Need help & moral support w/ truck issue
Question:
Agree that this is the most likely culprit.
– Hide quoted text — Show quoted text -> To: Patrick > I had a 1985 Nissan PU that did the exact same thing when I was camping at > Lake Isabella. It didn’t take very long to figure out that the exhaust was > pluged. The honey combs in the catalytic converter had broken loose and > pluged everything up so nothing could pass thru the exhaust system and that > was why everything was backing up thru the carburator. I took the exhaust > system apart and removed the honey combs that were cloging everything up and > the truck ran fine. I also had an ultralite airplane that sat for about six > months without being used. The bees had gone into the exhaust and hade their > home inside which also cloged the exhaust. The airplane would never get full > power. After I cleaned the exhaust on that engine, the plane ran fine. Is > what I am trying to say is, "Check your exhaust". > Steve from Lake Elsinore, Ca. > before you go nutz, try replacing the fouled spark plugs-just do it > its the cheapest and most probable cause of the problem you described > and dont use champions, they sometimes come pre-fouled from the > factory. R. > >Hi all, > >Sorry for the broad crosspost, but desperate times call for desperate > >measures. 
Please let me know if you have any ideas, since otherwise > >I’m probably going to have to get this thing towed to the garage, and > >have a huge bill for some guy to repeat the tests I’ve already done. > >Email is preferred, to cut down on spam, and since I don’t always get > >to reading these groups before they expire. > >I have a ‘79 GMC with a 454. It’s always run great, but I had to store > >it a few months ago. After not being run for a couple of months, I > >noticed that it started blowing unburned gas through the carburetor, > >which of course meant that it stumbled whenever that happened. As a > >result, I had to hold the gas pedal to about 2000 RPM or so, and just > >let the puffs of gas take their course, and then after it heated up > >a bit, it would idle poorly, but would at least run. Under load > >(low vacuum), it would also stumble and blow gas through the carb, > >until it was even warmer still. > >This situation got a little worse. Eventually, it got to be that even > >when it was warm, it would still puff out gas under load, and it took > >even longer to get it to "warm up." I did some inconclusive testing > >(see below), and changed the oil, after running engine cleaner for the > >recommended 5 minutes. > >Another few weeks passed, and the situation was significantly worse. > >I replaced the cap and rotor, and coming back to it a couple of days > >later, it didn’t even start at all! I noticed that the accelerator > >pump on the q-jet was leaking, as was the lower gasket. Figuring the > >carb was probably a big part of the problem, I replaced it with an > >Edelbrock. Minor improvement, since it no longer blows out clouds of > >misted gas, and runs a little under 1/4 throttle (more or less doesn’t > >seem to change the speed of the idle, and it appears to only run on > >2 cylinders or so, by the sound of it) > >Last night, I stuck an accel hei coil on it (it already had new wires). > >Again, no improvement. It looks like the battery is about dead, too, > >which is easily fixed, but I somehow doubt that it accounts for very > >much of the problem. > >What I do know is: compression is good, valve springs are good, valve > >"lash" is good (0), the problem got progressively worse over time and > >is worse cold, valve timing appears pretty close. No vacuum leaks, > >and I temporarily took off the smog stuff, to diagnose the issue. > >Unknowns: condition of the rest of the ignition system (condenser, > >ignition module), exact valve timing, whether the fact that it has a > >block-off plate over the EGR (which I assume is what the metal "tube" > >in the inside center of the manifold is for?) has anything to do with it. > >Speculation on what could be wrong: I’m running out of ideas! Originally > >I thought it may have been a valve that stuck at medium speeds (thus > >compression would be good, and high-RPM operation would be less > critical), > >but that wouldn’t explain why things are getting worse. I don’t know of > >any way to test for this. > >So, like I said, I’m completely out of ideas, and am hoping to not have > >to pay several hundreds more for a shop to try to fix it, especially > >after I’ve put about $500 into carburator, coil, and various other fixes. > >I thought about replacing the manifold, but that would be a bigger > >ordeal, and since it’s a truck with a 454 and a towing package, I’m > >not sure if it has tall-deck heads or not (or if that’s just used in > >bus engines!). > >I believe the original engine was replaced with an early-mid-80s engine, > >and like I said, the reason I bought this thing used in the first place > >was because the engine purred like a kitten. So, something really > strange > >is going on. Please help!! Argh! > >Thanks!! > > – Patrick
Response:
I also had similar problem. I ended up rebuilding carb several times only to find out that the vent tube to fuel tank was plugged. This caused the carb to load up and flood. When the heat of the mid-day expanded the fuel, it had no where to go so it took the only route it had, through the carb. Some types of carbs clog very easy and hold the needles open and they intern flood. I would install a clear fuel filter(second filter) and see what happens. Disconnect all sources of spark and run the fuel line into a jar, turn the engine over and see if there’s crap in the fuel. If the gas tank isn’t kept full when it’s parked for a while, it’s easy for the tank to develop fuel deposits in the tank. Good luck and I hope you find the problem before you spend a fortune to find the problem. Sincerely Rob H
– Hide quoted text — Show quoted text -> Had a similar problem with my 350 and replaced all the parts you did > and each replacement helped a little. Did fuel pump and intake manifold, > too. Also went over vacuum lines top to bottom. I would take > a good look at your fuel tank and filter. My tank was rusted after sitting > a *short* time at near empty. The fuel sock was torn so the carb injested a > ton of gunk and rust when I finally did restart it. Smelled terrible when it > ran, too. I double filtered it temporarily to ensure no more rust went > through. > Now the tank is out for repair. > Dale > Hi all, > Sorry for the broad crosspost, but desperate times call for desperate > measures. Please let me know if you have any ideas, since otherwise > I’m probably going to have to get this thing towed to the garage, and > have a huge bill for some guy to repeat the tests I’ve already done. > Email is preferred, to cut down on spam, and since I don’t always get > to reading these groups before they expire. > I have a ‘79 GMC with a 454. It’s always run great, but I had to store > it a few months ago. After not being run for a couple of months, I > noticed that it started blowing unburned gas through the carburetor, > which of course meant that it stumbled whenever that happened. As a > result, I had to hold the gas pedal to about 2000 RPM or so, and just > let the puffs of gas take their course, and then after it heated up > a bit, it would idle poorly, but would at least run. Under load > (low vacuum), it would also stumble and blow gas through the carb, > until it was even warmer still. > This situation got a little worse. Eventually, it got to be that even > when it was warm, it would still puff out gas under load, and it took > even longer to get it to "warm up." I did some inconclusive testing > (see below), and changed the oil, after running engine cleaner for the > recommended 5 minutes. > Another few weeks passed, and the situation was significantly worse. > I replaced the cap and rotor, and coming back to it a couple of days > later, it didn’t even start at all! I noticed that the accelerator > pump on the q-jet was leaking, as was the lower gasket. Figuring the > carb was probably a big part of the problem, I replaced it with an > Edelbrock. Minor improvement, since it no longer blows out clouds of > misted gas, and runs a little under 1/4 throttle (more or less doesn’t > seem to change the speed of the idle, and it appears to only run on > 2 cylinders or so, by the sound of it) > Last night, I stuck an accel hei coil on it (it already had new wires). > Again, no improvement. It looks like the battery is about dead, too, > which is easily fixed, but I somehow doubt that it accounts for very > much of the problem. > What I do know is: compression is good, valve springs are good, valve > "lash" is good (0), the problem got progressively worse over time and > is worse cold, valve timing appears pretty close. No vacuum leaks, > and I temporarily took off the smog stuff, to diagnose the issue. > Unknowns: condition of the rest of the ignition system (condenser, > ignition module), exact valve timing, whether the fact that it has a > block-off plate over the EGR (which I assume is what the metal "tube" > in the inside center of the manifold is for?) has anything to do with it. > Speculation on what could be wrong: I’m running out of ideas! Originally > I thought it may have been a valve that stuck at medium speeds (thus > compression would be good, and high-RPM operation would be less critical), > but that wouldn’t explain why things are getting worse. I don’t know of > any way to test for this. > So, like I said, I’m completely out of ideas, and am hoping to not have > to pay several hundreds more for a shop to try to fix it, especially > after I’ve put about $500 into carburator, coil, and various other fixes. > I thought about replacing the manifold, but that would be a bigger > ordeal, and since it’s a truck with a 454 and a towing package, I’m > not sure if it has tall-deck heads or not (or if that’s just used in > bus engines!). > I believe the original engine was replaced with an early-mid-80s engine, > and like I said, the reason I bought this thing used in the first place > was because the engine purred like a kitten. So, something really strange > is going on. Please help!! Argh! > Thanks!! > - Patrick
Response:
OUCH – That could hurt – in an airplane, you can’t exactly just pull over when you lose power… — ‘There is no substitute for cubic inches’ Chris Wisneski Cad Company www.cad500parts.com Originators of 8.2 Liter Performance (505)823-9840
– Hide quoted text — Show quoted text -> To: Patrick > I had a 1985 Nissan PU that did the exact same thing when I was camping at > Lake Isabella. It didn’t take very long to figure out that the exhaust was > pluged. The honey combs in the catalytic converter had broken loose and > pluged everything up so nothing could pass thru the exhaust system and that > was why everything was backing up thru the carburator. I took the exhaust > system apart and removed the honey combs that were cloging everything up and > the truck ran fine. I also had an ultralite airplane that sat for about six > months without being used. The bees had gone into the exhaust and hade their > home inside which also cloged the exhaust. The airplane would never get full > power. After I cleaned the exhaust on that engine, the plane ran fine. Is > what I am trying to say is, "Check your exhaust". > Steve from Lake Elsinore, Ca. > before you go nutz, try replacing the fouled spark plugs-just do it > its the cheapest and most probable cause of the problem you described > and dont use champions, they sometimes come pre-fouled from the > factory. R. > >Hi all, > >Sorry for the broad crosspost, but desperate times call for desperate > >measures. Please let me know if you have any ideas, since otherwise > >I’m probably going to have to get this thing towed to the garage, and > >have a huge bill for some guy to repeat the tests I’ve already done. > >Email is preferred, to cut down on spam, and since I don’t always get > >to reading these groups before they expire. > >I have a ‘79 GMC with a 454. It’s always run great, but I had to store > >it a few months ago. After not being run for a couple of months, I > >noticed that it started blowing unburned gas through the carburetor, > >which of course meant that it stumbled whenever that happened. As a > >result, I had to hold the gas pedal to about 2000 RPM or so, and just > >let the puffs of gas take their course, and then after it heated up > >a bit, it would idle poorly, but would at least run. Under load > >(low vacuum), it would also stumble and blow gas through the carb, > >until it was even warmer still. > >This situation got a little worse. Eventually, it got to be that even > >when it was warm, it would still puff out gas under load, and it took > >even longer to get it to "warm up." I did some inconclusive testing > >(see below), and changed the oil, after running engine cleaner for the > >recommended 5 minutes. > >Another few weeks passed, and the situation was significantly worse. > >I replaced the cap and rotor, and coming back to it a couple of days > >later, it didn’t even start at all! I noticed that the accelerator > >pump on the q-jet was leaking, as was the lower gasket. Figuring the > >carb was probably a big part of the problem, I replaced it with an > >Edelbrock. Minor improvement, since it no longer blows out clouds of > >misted gas, and runs a little under 1/4 throttle (more or less doesn’t > >seem to change the speed of the idle, and it appears to only run on > >2 cylinders or so, by the sound of it) > >Last night, I stuck an accel hei coil on it (it already had new wires). > >Again, no improvement. It looks like the battery is about dead, too, > >which is easily fixed, but I somehow doubt that it accounts for very > >much of the problem. > >What I do know is: compression is good, valve springs are good, valve > >"lash" is good (0), the problem got progressively worse over time and > >is worse cold, valve timing appears pretty close. No vacuum leaks, > >and I temporarily took off the smog stuff, to diagnose the issue. > >Unknowns: condition of the rest of the ignition system (condenser, > >ignition module), exact valve timing, whether the fact that it has a > >block-off plate over the EGR (which I assume is what the metal "tube" > >in the inside center of the manifold is for?) has anything to do with it. > >Speculation on what could be wrong: I’m running out of ideas! Originally > >I thought it may have been a valve that stuck at medium speeds (thus > >compression would be good, and high-RPM operation would be less > critical), > >but that wouldn’t explain why things are getting worse. I don’t know of > >any way to test for this. > >So, like I said, I’m completely out of ideas, and am hoping to not have > >to pay several hundreds more for a shop to try to fix it, especially > >after I’ve put about $500 into carburator, coil, and various other fixes. > >I thought about replacing the manifold, but that would be a bigger > >ordeal, and since it’s a truck with a 454 and a towing package, I’m > >not sure if it has tall-deck heads or not (or if that’s just used in > >bus engines!). > >I believe the original engine was replaced with an early-mid-80s engine, > >and like I said, the reason I bought this thing used in the first place > >was because the engine purred like a kitten. So, something really > strange > >is going on. Please help!! Argh! > >Thanks!! > > – Patrick
Response:
To: Patrick I had a 1985 Nissan PU that did the exact same thing when I was camping at Lake Isabella. It didn’t take very long to figure out that the exhaust was pluged. The honey combs in the catalytic converter had broken loose and pluged everything up so nothing could pass thru the exhaust system and that was why everything was backing up thru the carburator. I took the exhaust system apart and removed the honey combs that were cloging everything up and the truck ran fine. I also had an ultralite airplane that sat for about six months without being used. The bees had gone into the exhaust and hade their home inside which also cloged the exhaust. The airplane would never get full power. After I cleaned the exhaust on that engine, the plane ran fine. Is what I am trying to say is, "Check your exhaust". Steve from Lake Elsinore, Ca.
– Hide quoted text — Show quoted text -> before you go nutz, try replacing the fouled spark plugs-just do it > its the cheapest and most probable cause of the problem you described > and dont use champions, they sometimes come pre-fouled from the > factory. R. >Hi all, >Sorry for the broad crosspost, but desperate times call for desperate >measures. Please let me know if you have any ideas, since otherwise >I’m probably going to have to get this thing towed to the garage, and >have a huge bill for some guy to repeat the tests I’ve already done. >Email is preferred, to cut down on spam, and since I don’t always get >to reading these groups before they expire. >I have a ‘79 GMC with a 454. It’s always run great, but I had to store >it a few months ago. After not being run for a couple of months, I >noticed that it started blowing unburned gas through the carburetor, >which of course meant that it stumbled whenever that happened. As a >result, I had to hold the gas pedal to about 2000 RPM or so, and just >let the puffs of gas take their course, and then after it heated up >a bit, it would idle poorly, but would at least run. Under load >(low vacuum), it would also stumble and blow gas through the carb, >until it was even warmer still. >This situation got a little worse. Eventually, it got to be that even >when it was warm, it would still puff out gas under load, and it took >even longer to get it to "warm up." I did some inconclusive testing >(see below), and changed the oil, after running engine cleaner for the >recommended 5 minutes. >Another few weeks passed, and the situation was significantly worse. >I replaced the cap and rotor, and coming back to it a couple of days >later, it didn’t even start at all! I noticed that the accelerator >pump on the q-jet was leaking, as was the lower gasket. Figuring the >carb was probably a big part of the problem, I replaced it with an >Edelbrock. Minor improvement, since it no longer blows out clouds of >misted gas, and runs a little under 1/4 throttle (more or less doesn’t >seem to change the speed of the idle, and it appears to only run on >2 cylinders or so, by the sound of it) >Last night, I stuck an accel hei coil on it (it already had new wires). >Again, no improvement. It looks like the battery is about dead, too, >which is easily fixed, but I somehow doubt that it accounts for very >much of the problem. >What I do know is: compression is good, valve springs are good, valve >"lash" is good (0), the problem got progressively worse over time and >is worse cold, valve timing appears pretty close. No vacuum leaks, >and I temporarily took off the smog stuff, to diagnose the issue. >Unknowns: condition of the rest of the ignition system (condenser, >ignition module), exact valve timing, whether the fact that it has a >block-off plate over the EGR (which I assume is what the metal "tube" >in the inside center of the manifold is for?) has anything to do with it. >Speculation on what could be wrong: I’m running out of ideas! Originally >I thought it may have been a valve that stuck at medium speeds (thus >compression would be good, and high-RPM operation would be less critical), >but that wouldn’t explain why things are getting worse. I don’t know of >any way to test for this. >So, like I said, I’m completely out of ideas, and am hoping to not have >to pay several hundreds more for a shop to try to fix it, especially >after I’ve put about $500 into carburator, coil, and various other fixes. >I thought about replacing the manifold, but that would be a bigger >ordeal, and since it’s a truck with a 454 and a towing package, I’m >not sure if it has tall-deck heads or not (or if that’s just used in >bus engines!). >I believe the original engine was replaced with an early-mid-80s engine, >and like I said, the reason I bought this thing used in the first place >was because the engine purred like a kitten. So, something really strange >is going on. Please help!! Argh! >Thanks!! > – Patrick
Response:
before you go nutz, try replacing the fouled spark plugs-just do it its the cheapest and most probable cause of the problem you described and dont use champions, they sometimes come pre-fouled from the factory. R. – Hide quoted text — Show quoted text – >Hi all, >Sorry for the broad crosspost, but desperate times call for desperate >measures. Please let me know if you have any ideas, since otherwise >I’m probably going to have to get this thing towed to the garage, and >have a huge bill for some guy to repeat the tests I’ve already done. >Email is preferred, to cut down on spam, and since I don’t always get >to reading these groups before they expire. >I have a ‘79 GMC with a 454. It’s always run great, but I had to store >it a few months ago. After not being run for a couple of months, I >noticed that it started blowing unburned gas through the carburetor, >which of course meant that it stumbled whenever that happened. As a >result, I had to hold the gas pedal to about 2000 RPM or so, and just >let the puffs of gas take their course, and then after it heated up >a bit, it would idle poorly, but would at least run. Under load >(low vacuum), it would also stumble and blow gas through the carb, >until it was even warmer still. >This situation got a little worse. Eventually, it got to be that even >when it was warm, it would still puff out gas under load, and it took >even longer to get it to "warm up." I did some inconclusive testing >(see below), and changed the oil, after running engine cleaner for the >recommended 5 minutes. >Another few weeks passed, and the situation was significantly worse. >I replaced the cap and rotor, and coming back to it a couple of days >later, it didn’t even start at all! I noticed that the accelerator >pump on the q-jet was leaking, as was the lower gasket. Figuring the >carb was probably a big part of the problem, I replaced it with an >Edelbrock. Minor improvement, since it no longer blows out clouds of >misted gas, and runs a little under 1/4 throttle (more or less doesn’t >seem to change the speed of the idle, and it appears to only run on >2 cylinders or so, by the sound of it) >Last night, I stuck an accel hei coil on it (it already had new wires). >Again, no improvement. It looks like the battery is about dead, too, >which is easily fixed, but I somehow doubt that it accounts for very >much of the problem. >What I do know is: compression is good, valve springs are good, valve >"lash" is good (0), the problem got progressively worse over time and >is worse cold, valve timing appears pretty close. No vacuum leaks, >and I temporarily took off the smog stuff, to diagnose the issue. >Unknowns: condition of the rest of the ignition system (condenser, >ignition module), exact valve timing, whether the fact that it has a >block-off plate over the EGR (which I assume is what the metal "tube" >in the inside center of the manifold is for?) has anything to do with it. >Speculation on what could be wrong: I’m running out of ideas! Originally >I thought it may have been a valve that stuck at medium speeds (thus >compression would be good, and high-RPM operation would be less critical), >but that wouldn’t explain why things are getting worse. I don’t know of >any way to test for this. >So, like I said, I’m completely out of ideas, and am hoping to not have >to pay several hundreds more for a shop to try to fix it, especially >after I’ve put about $500 into carburator, coil, and various other fixes. >I thought about replacing the manifold, but that would be a bigger >ordeal, and since it’s a truck with a 454 and a towing package, I’m >not sure if it has tall-deck heads or not (or if that’s just used in >bus engines!). >I believe the original engine was replaced with an early-mid-80s engine, >and like I said, the reason I bought this thing used in the first place >was because the engine purred like a kitten. So, something really strange >is going on. Please help!! Argh! >Thanks!! > – Patrick
Response:
Had a similar problem with my 350 and replaced all the parts you did and each replacement helped a little. Did fuel pump and intake manifold, too. Also went over vacuum lines top to bottom. I would take a good look at your fuel tank and filter. My tank was rusted after sitting a *short* time at near empty. The fuel sock was torn so the carb injested a ton of gunk and rust when I finally did restart it. Smelled terrible when it ran, too. I double filtered it temporarily to ensure no more rust went through. Now the tank is out for repair. Dale
– Hide quoted text — Show quoted text -> Hi all, > Sorry for the broad crosspost, but desperate times call for desperate > measures. Please let me know if you have any ideas, since otherwise > I’m probably going to have to get this thing towed to the garage, and > have a huge bill for some guy to repeat the tests I’ve already done. > Email is preferred, to cut down on spam, and since I don’t always get > to reading these groups before they expire. > I have a ‘79 GMC with a 454. It’s always run great, but I had to store > it a few months ago. After not being run for a couple of months, I > noticed that it started blowing unburned gas through the carburetor, > which of course meant that it stumbled whenever that happened. As a > result, I had to hold the gas pedal to about 2000 RPM or so, and just > let the puffs of gas take their course, and then after it heated up > a bit, it would idle poorly, but would at least run. Under load > (low vacuum), it would also stumble and blow gas through the carb, > until it was even warmer still. > This situation got a little worse. Eventually, it got to be that even > when it was warm, it would still puff out gas under load, and it took > even longer to get it to "warm up." I did some inconclusive testing > (see below), and changed the oil, after running engine cleaner for the > recommended 5 minutes. > Another few weeks passed, and the situation was significantly worse. > I replaced the cap and rotor, and coming back to it a couple of days > later, it didn’t even start at all! I noticed that the accelerator > pump on the q-jet was leaking, as was the lower gasket. Figuring the > carb was probably a big part of the problem, I replaced it with an > Edelbrock. Minor improvement, since it no longer blows out clouds of > misted gas, and runs a little under 1/4 throttle (more or less doesn’t > seem to change the speed of the idle, and it appears to only run on > 2 cylinders or so, by the sound of it) > Last night, I stuck an accel hei coil on it (it already had new wires). > Again, no improvement. It looks like the battery is about dead, too, > which is easily fixed, but I somehow doubt that it accounts for very > much of the problem. > What I do know is: compression is good, valve springs are good, valve > "lash" is good (0), the problem got progressively worse over time and > is worse cold, valve timing appears pretty close. No vacuum leaks, > and I temporarily took off the smog stuff, to diagnose the issue. > Unknowns: condition of the rest of the ignition system (condenser, > ignition module), exact valve timing, whether the fact that it has a > block-off plate over the EGR (which I assume is what the metal "tube" > in the inside center of the manifold is for?) has anything to do with it. > Speculation on what could be wrong: I’m running out of ideas! Originally > I thought it may have been a valve that stuck at medium speeds (thus > compression would be good, and high-RPM operation would be less critical), > but that wouldn’t explain why things are getting worse. I don’t know of > any way to test for this. > So, like I said, I’m completely out of ideas, and am hoping to not have > to pay several hundreds more for a shop to try to fix it, especially > after I’ve put about $500 into carburator, coil, and various other fixes. > I thought about replacing the manifold, but that would be a bigger > ordeal, and since it’s a truck with a 454 and a towing package, I’m > not sure if it has tall-deck heads or not (or if that’s just used in > bus engines!). > I believe the original engine was replaced with an early-mid-80s engine, > and like I said, the reason I bought this thing used in the first place > was because the engine purred like a kitten. So, something really strange > is going on. Please help!! Argh! > Thanks!! > - Patrick
Response:
Also check the exhaust system for a stopped up muffler or cat convertor. Alan – Hide quoted text — Show quoted text – > Hi all, > Sorry for the broad crosspost, but desperate times call for desperate > measures. Please let me know if you have any ideas, since otherwise > I’m probably going to have to get this thing towed to the garage, and > have a huge bill for some guy to repeat the tests I’ve already done. > Email is preferred, to cut down on spam, and since I don’t always get > to reading these groups before they expire. > I have a ‘79 GMC with a 454. It’s always run great, but I had to store > it a few months ago. After not being run for a couple of months, I > noticed that it started blowing unburned gas through the carburetor, > which of course meant that it stumbled whenever that happened. As a > result, I had to hold the gas pedal to about 2000 RPM or so, and just > let the puffs of gas take their course, and then after it heated up > a bit, it would idle poorly, but would at least run. Under load > (low vacuum), it would also stumble and blow gas through the carb, > until it was even warmer still. > This situation got a little worse. Eventually, it got to be that even > when it was warm, it would still puff out gas under load, and it took > even longer to get it to "warm up." I did some inconclusive testing > (see below), and changed the oil, after running engine cleaner for the > recommended 5 minutes. > Another few weeks passed, and the situation was significantly worse. > I replaced the cap and rotor, and coming back to it a couple of days > later, it didn’t even start at all! I noticed that the accelerator > pump on the q-jet was leaking, as was the lower gasket. Figuring the > carb was probably a big part of the problem, I replaced it with an > Edelbrock. Minor improvement, since it no longer blows out clouds of > misted gas, and runs a little under 1/4 throttle (more or less doesn’t > seem to change the speed of the idle, and it appears to only run on > 2 cylinders or so, by the sound of it) > Last night, I stuck an accel hei coil on it (it already had new wires). > Again, no improvement. It looks like the battery is about dead, too, > which is easily fixed, but I somehow doubt that it accounts for very > much of the problem. > What I do know is: compression is good, valve springs are good, valve > "lash" is good (0), the problem got progressively worse over time and > is worse cold, valve timing appears pretty close. No vacuum leaks, > and I temporarily took off the smog stuff, to diagnose the issue. > Unknowns: condition of the rest of the ignition system (condenser, > ignition module), exact valve timing, whether the fact that it has a > block-off plate over the EGR (which I assume is what the metal "tube" > in the inside center of the manifold is for?) has anything to do with it. > Speculation on what could be wrong: I’m running out of ideas! Originally > I thought it may have been a valve that stuck at medium speeds (thus > compression would be good, and high-RPM operation would be less critical), > but that wouldn’t explain why things are getting worse. I don’t know of > any way to test for this. > So, like I said, I’m completely out of ideas, and am hoping to not have > to pay several hundreds more for a shop to try to fix it, especially > after I’ve put about $500 into carburator, coil, and various other fixes. > I thought about replacing the manifold, but that would be a bigger > ordeal, and since it’s a truck with a 454 and a towing package, I’m > not sure if it has tall-deck heads or not (or if that’s just used in > bus engines!). > I believe the original engine was replaced with an early-mid-80s engine, > and like I said, the reason I bought this thing used in the first place > was because the engine purred like a kitten. So, something really strange > is going on. Please help!! Argh! > Thanks!! > - Patrick
Response:
Have you replaced the timing chain? Sounds like it has worn and possibly slipped. This would cause the back fire of fuel through the carb. Be careful! A spark while testing for ignition spark "WILL" ignite this fuel! I found out the hard way! Keith
– Hide quoted text — Show quoted text -> Also check the exhaust system for a stopped up muffler or cat convertor.
Response:
I would still look at timing; probably valve, or sticky valve(s) My thoughts: For Crissake don’t blow yourelf up! Check for spark (timing light) on all pots under various engine conditions. Look especially for wander or intermittent spark, which could indicate worn/damaged/loose parts on dizzy (including the shaft) Check spark timing on all pots (you will need to mark the timing pulley with other chalk marks at the correct angles) See above…. If that’s OK: If it’s running rough, find out which pots don’t make a difference (remove plug leads) replace all plug leads but one of the ones that make no difference then remove _plugs_ that make no difference, one by one, running the engine each time, until you find one (or ones!) that stops the fuel blowback (if you do!). If the engine runs without a plug in the pot, and there is no fuel blowback , then that is the faulty pot/valve. It may of course be that there is more than one. This could be caused by sticky valves of slipping timing chain. If you can isolate to a particular pot, then it’s valve. I would have though that a timing chain problem would get worse and worse, and that all pts would finally die. – Hide quoted text — Show quoted text ->Hi all, >Sorry for the broad crosspost, but desperate times call for desperate >measures. Please let me know if you have any ideas, since otherwise >I’m probably going to have to get this thing towed to the garage, and >have a huge bill for some guy to repeat the tests I’ve already done. >Email is preferred, to cut down on spam, and since I don’t always get >to reading these groups before they expire. >I have a ‘79 GMC with a 454. It’s always run great, but I had to store >it a few months ago. After not being run for a couple of months, I >noticed that it started blowing unburned gas through the carburetor, >which of course meant that it stumbled whenever that happened. As a >result, I had to hold the gas pedal to about 2000 RPM or so, and just >let the puffs of gas take their course, and then after it heated up >a bit, it would idle poorly, but would at least run. Under load >(low vacuum), it would also stumble and blow gas through the carb, >until it was even warmer still. >This situation got a little worse. Eventually, it got to be that even >when it was warm, it would still puff out gas under load, and it took >even longer to get it to "warm up." I did some inconclusive testing >(see below), and changed the oil, after running engine cleaner for the >recommended 5 minutes. >Another few weeks passed, and the situation was significantly worse. >I replaced the cap and rotor, and coming back to it a couple of days >later, it didn’t even start at all! I noticed that the accelerator >pump on the q-jet was leaking, as was the lower gasket. Figuring the >carb was probably a big part of the problem, I replaced it with an >Edelbrock. Minor improvement, since it no longer blows out clouds of >misted gas, and runs a little under 1/4 throttle (more or less doesn’t >seem to change the speed of the idle, and it appears to only run on >2 cylinders or so, by the sound of it) >Last night, I stuck an accel hei coil on it (it already had new wires). >Again, no improvement. It looks like the battery is about dead, too, >which is easily fixed, but I somehow doubt that it accounts for very >much of the problem. >What I do know is: compression is good, valve springs are good, valve >"lash" is good (0), the problem got progressively worse over time and >is worse cold, valve timing appears pretty close. No vacuum leaks, >and I temporarily took off the smog stuff, to diagnose the issue. >Unknowns: condition of the rest of the ignition system (condenser, >ignition module), exact valve timing, whether the fact that it has a >block-off plate over the EGR (which I assume is what the metal "tube" >in the inside center of the manifold is for?) has anything to do with it. >Speculation on what could be wrong: I’m running out of ideas! Originally >I thought it may have been a valve that stuck at medium speeds (thus >compression would be good, and high-RPM operation would be less critical), >but that wouldn’t explain why things are getting worse. I don’t know of >any way to test for this. >So, like I said, I’m completely out of ideas, and am hoping to not have >to pay several hundreds more for a shop to try to fix it, especially >after I’ve put about $500 into carburator, coil, and various other fixes. >I thought about replacing the manifold, but that would be a bigger >ordeal, and since it’s a truck with a 454 and a towing package, I’m >not sure if it has tall-deck heads or not (or if that’s just used in >bus engines!). >I believe the original engine was replaced with an early-mid-80s engine, >and like I said, the reason I bought this thing used in the first place >was because the engine purred like a kitten. So, something really strange >is going on. Please help!! Argh! >Thanks!! > – Patrick
Nick White — HEAD:Hertz Music ….damn spam !! <") _/ ) ( ) _//- __/
Response:
- Hide quoted text — Show quoted text – > Hi all, > Sorry for the broad crosspost, but desperate times call for desperate > measures. Please let me know if you have any ideas, since otherwise > I’m probably going to have to get this thing towed to the garage, and > have a huge bill for some guy to repeat the tests I’ve already done. > Email is preferred, to cut down on spam, and since I don’t always get > to reading these groups before they expire. > I have a ‘79 GMC with a 454. It’s always run great, but I had to store > it a few months ago. After not being run for a couple of months, I > noticed that it started blowing unburned gas through the carburetor, > which of course meant that it stumbled whenever that happened. As a > result, I had to hold the gas pedal to about 2000 RPM or so, and just > let the puffs of gas take their course, and then after it heated up > a bit, it would idle poorly, but would at least run. Under load > (low vacuum), it would also stumble and blow gas through the carb, > until it was even warmer still. > This situation got a little worse. Eventually, it got to be that even > when it was warm, it would still puff out gas under load, and it took > even longer to get it to "warm up." I did some inconclusive testing > (see below), and changed the oil, after running engine cleaner for the > recommended 5 minutes. > Another few weeks passed, and the situation was significantly worse. > I replaced the cap and rotor, and coming back to it a couple of days > later, it didn’t even start at all! I noticed that the accelerator > pump on the q-jet was leaking, as was the lower gasket. Figuring the > carb was probably a big part of the problem, I replaced it with an > Edelbrock. Minor improvement, since it no longer blows out clouds of > misted gas, and runs a little under 1/4 throttle (more or less doesn’t > seem to change the speed of the idle, and it appears to only run on > 2 cylinders or so, by the sound of it) > Last night, I stuck an accel hei coil on it (it already had new wires). > Again, no improvement. It looks like the battery is about dead, too, > which is easily fixed, but I somehow doubt that it accounts for very > much of the problem. > What I do know is: compression is good, valve springs are good, valve > "lash" is good (0), the problem got progressively worse over time and > is worse cold, valve timing appears pretty close. No vacuum leaks, > and I temporarily took off the smog stuff, to diagnose the issue. > Unknowns: condition of the rest of the ignition system (condenser, > ignition module), exact valve timing, whether the fact that it has a > block-off plate over the EGR (which I assume is what the metal "tube" > in the inside center of the manifold is for?) has anything to do with it. > Speculation on what could be wrong: I’m running out of ideas! Originally > I thought it may have been a valve that stuck at medium speeds (thus > compression would be good, and high-RPM operation would be less critical), > but that wouldn’t explain why things are getting worse. I don’t know of > any way to test for this. > So, like I said, I’m completely out of ideas, and am hoping to not have > to pay several hundreds more for a shop to try to fix it, especially > after I’ve put about $500 into carburator, coil, and various other fixes. > I thought about replacing the manifold, but that would be a bigger > ordeal, and since it’s a truck with a 454 and a towing package, I’m > not sure if it has tall-deck heads or not (or if that’s just used in > bus engines!). > I believe the original engine was replaced with an early-mid-80s engine, > and like I said, the reason I bought this thing used in the first place > was because the engine purred like a kitten. So, something really strange > is going on. Please help!! Argh! > Thanks!! > - Patrick
I think before you buy any more parts trying to fix it you should pay a shop to check it I would have the timing checked with a timing light It could have jumped time. Have you checked the fuel pump? It could be almost anything and will be hard for someone to diagnose over the net. Good luck. Steve
Response:
Hi all, Sorry for the broad crosspost, but desperate times call for desperate measures. Please let me know if you have any ideas, since otherwise I’m probably going to have to get this thing towed to the garage, and have a huge bill for some guy to repeat the tests I’ve already done. Email is preferred, to cut down on spam, and since I don’t always get to reading these groups before they expire. I have a ‘79 GMC with a 454. It’s always run great, but I had to store it a few months ago. After not being run for a couple of months, I noticed that it started blowing unburned gas through the carburetor, which of course meant that it stumbled whenever that happened. As a result, I had to hold the gas pedal to about 2000 RPM or so, and just let the puffs of gas take their course, and then after it heated up a bit, it would idle poorly, but would at least run. Under load (low vacuum), it would also stumble and blow gas through the carb, until it was even warmer still. This situation got a little worse. Eventually, it got to be that even when it was warm, it would still puff out gas under load, and it took even longer to get it to "warm up." I did some inconclusive testing (see below), and changed the oil, after running engine cleaner for the recommended 5 minutes. Another few weeks passed, and the situation was significantly worse. I replaced the cap and rotor, and coming back to it a couple of days later, it didn’t even start at all! I noticed that the accelerator pump on the q-jet was leaking, as was the lower gasket. Figuring the carb was probably a big part of the problem, I replaced it with an Edelbrock. Minor improvement, since it no longer blows out clouds of misted gas, and runs a little under 1/4 throttle (more or less doesn’t seem to change the speed of the idle, and it appears to only run on 2 cylinders or so, by the sound of it) Last night, I stuck an accel hei coil on it (it already had new wires). Again, no improvement. It looks like the battery is about dead, too, which is easily fixed, but I somehow doubt that it accounts for very much of the problem. What I do know is: compression is good, valve springs are good, valve "lash" is good (0), the problem got progressively worse over time and is worse cold, valve timing appears pretty close. No vacuum leaks, and I temporarily took off the smog stuff, to diagnose the issue. Unknowns: condition of the rest of the ignition system (condenser, ignition module), exact valve timing, whether the fact that it has a block-off plate over the EGR (which I assume is what the metal "tube" in the inside center of the manifold is for?) has anything to do with it. Speculation on what could be wrong: I’m running out of ideas! Originally I thought it may have been a valve that stuck at medium speeds (thus compression would be good, and high-RPM operation would be less critical), but that wouldn’t explain why things are getting worse. I don’t know of any way to test for this. So, like I said, I’m completely out of ideas, and am hoping to not have to pay several hundreds more for a shop to try to fix it, especially after I’ve put about $500 into carburator, coil, and various other fixes. I thought about replacing the manifold, but that would be a bigger ordeal, and since it’s a truck with a 454 and a towing package, I’m not sure if it has tall-deck heads or not (or if that’s just used in bus engines!). I believe the original engine was replaced with an early-mid-80s engine, and like I said, the reason I bought this thing used in the first place was because the engine purred like a kitten. So, something really strange is going on. Please help!! Argh! Thanks!! - Patrick
