86 carburator mixture control valve
Question:
On my full size 86 Blazer the computer was high on the inside of the firewall behind and above the glove box. It might be behind some loose insulation. If I remember right it has minimal control, spark retard (knock sensor), and working with the temp for the control on the carb. It’s been awhile since I worked on it, I replaced it with a later model TBI system. I think the only signal it got was either on or off. Here again not real sure, can’t find my manuals. – Hide quoted text — Show quoted text – > scratch the vacuum…too many sensors here…I’m trying to make some sense > outta this manual. Let me tell you, the factory service manuals are nothing > like they were in the 60’s and 70’s! > According to the book, my truck has a computer too, but I’d sure like to > know where they hid it. It looks to me like the computer trucks in 86 were > the California models. I’ll see if I can’t figure out these diagrams a > little more when I get off work.
Response:
what you have is the predecessor to full blown computer engine management…most mid eighties gm trucks had this setup. believe it or not there is an ecm module located under the dash, but it’s primary function is to monitor ignition timing and fuel mixture.
Response:
Okay were exactly is this module, and do we have volatage specs for it? And what kind of input does it need or get to operate?
– Hide quoted text — Show quoted text -> what you have is the predecessor to full blown computer engine > management…most mid eighties gm trucks had this setup. believe it or not > there is an ecm module located under the dash, but it’s primary function is > to monitor ignition timing and fuel mixture.
Response:
the module is behind the glovebox on my 85 Blazer…open the glovebox and pull it all the way down so you can look in behind it, the module should be on a bracket to your left as you peer into the glovebox opening…you may have to root around a little to find it..look for a wide flat plug connected to a silver box that measures about 4×6. This is the ecm, or what passes for one anyway. According to the manual it mainly monitors ignition timing and can change timing in the event of severe knocking to prevent detonation. It has a knock sensor mounted on the side of the engine block to help it accomplish this. The signal sent from the knock sensor is a on/off type signal with no signal causing the ecm to retard the timing when engine knock is detected and a voltage of 8-10v during normal operation (no knock). This system was referred to as ESC or Electronic Spark Control. My 81 stepside even has a nameplate below the K10 plate on the fender proclaiming Electronic Spark Control, so apparently GM was quite proud of it’s little invention. Oddly enough, It is hard to find any detailed information on this early ecm…most manuals only briefly mention it before moving on to the next generation with flash codes and such. Who knows why they decided to throw the fuel mixture solenoid into the mix, unless it changes the fuel mixture when the engine is cold. I think it only has the one temp sensor for feedback, as you mentioned. The use of this as an accelerator pump solenoid would seem to explain the lack of anything else in the system. As far as "take all that smog pump crap off" goes, I’m still paying the price for a previous owner’s ignorance on my stepside. I agree with the take it all off and start from scratch or leave it alone point of view, but I would have opted for leave it alone, myself! After fixing countless vacuum leaks, rewiring half the engine compartment and scratching my head trying to figure out just exactly how much advance I have in the unknown pre-ESC distributor someone has put on this truck, I can finally say it sorta runs halfway decent some of the time.
Response:
scratch the vacuum…too many sensors here…I’m trying to make some sense outta this manual. Let me tell you, the factory service manuals are nothing like they were in the 60’s and 70’s! According to the book, my truck has a computer too, but I’d sure like to know where they hid it. It looks to me like the computer trucks in 86 were the California models. I’ll see if I can’t figure out these diagrams a little more when I get off work.
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| > I didn’t get the entire post, but are you talking about the 2-wire plug on | > the pass side front? | Yes it is, and it is supposed to be getting a signal from a small computer | under the dash so I’m told. | Now do you know what voltage it is suppose to send out to the mixture | control valve on the carb? | | This is a 2-stage accelerator pump, and it’s controlled totally by | temperature and vacuum controls. | | Temp yes, vacumn?! | And where does this small computer get it’s input from? | There is no O2 sensor on this motor | | I have the same 86 | > setup in my K1500 305. It basically gives twice the "squirt" when it’s | cold | > to aid in cold engine operation. | > | > Just taking that "smog pump crap" off is the worst mistake most people | ever | > make. Why? These setups (my 86 is a good example) are complex systems | (key | > word-system) that use many sensors, switches, and other things. If you | take | > away just one piece of the "system" you’ve pretty much rendered the whole | > thing useless. What it amounts to, is either leave it alone, or take it | ALL | > off. And the latter is not something a non-knowledgeable person with a | > "generic" Chiltons manual should be attempting. On the other hand, if you | > know your stuff, feel free to alter and test, alter and test, alter and | test | > until you find your "happy place." | > | > I hate it when someone just blurts out "rip it all off–it’s crap anyway" | to | > these newgroups. You just don’t know what kind of heartache you’re going | to | > cause somebody. | > | > | > | > | I know it’s a computer carb, but where does it get it signal? | > | Any CERTIFIED Chevy mechanics seen this setup? | > | | > | > I believe it a computer carb that was SUPPOSE to help Pollution. 87 | and | > up | > | > went to EFI. take that smog pump crap off, I did and seen a 16 pounds | of | > | > torque incase at the real wheels and still passed the emission. I had | it | > | put | > | > on a dyno(did some performance tuning) | > | > | > | > > Do you have one on your 86? | > | > > And if so why? | > | > > I don’t have a computer to open and close it, so why would Chevy put | > one | > | > > there? | > | > > It has 2 wires that one runs to the TVS on the upper waterneck hose | > and | > | > the | > | > > other goes into the firewall, underneath the dash I’m assuming? | > | > > I don’t have an O2 sensor either, so this does not make any sense to | > me! | > | > > And I don’t have a Check Engine Light either so the motor is not a | CCC | > | or | > | > C4 | > | > > System. | > | > > I do have a cat, and a airpump thought and all related smog hoses! | > | > > A Hybrid maybe?!!! | > | > > Can someone explain! | > | > > | > | > > | > | > | > | > | > | | > | | > | > | |
Response:
Do you have one on your 86? And if so why? I don’t have a computer to open and close it, so why would Chevy put one there? It has 2 wires that one runs to the TVS on the upper waterneck hose and the other goes into the firewall, underneath the dash I’m assuming? I don’t have an O2 sensor either, so this does not make any sense to me! And I don’t have a Check Engine Light either so the motor is not a CCC or C4 System. I do have a cat, and a airpump thought and all related smog hoses! A Hybrid maybe?!!! Can someone explain!
Response:
I believe it a computer carb that was SUPPOSE to help Pollution. 87 and up went to EFI. take that smog pump crap off, I did and seen a 16 pounds of torque incase at the real wheels and still passed the emission. I had it put on a dyno(did some performance tuning)
– Hide quoted text — Show quoted text -> Do you have one on your 86? > And if so why? > I don’t have a computer to open and close it, so why would Chevy put one > there? > It has 2 wires that one runs to the TVS on the upper waterneck hose and the > other goes into the firewall, underneath the dash I’m assuming? > I don’t have an O2 sensor either, so this does not make any sense to me! > And I don’t have a Check Engine Light either so the motor is not a CCC or C4 > System. > I do have a cat, and a airpump thought and all related smog hoses! > A Hybrid maybe?!!! > Can someone explain!
Response:
I know it’s a computer carb, but where does it get it signal? Any CERTIFIED Chevy mechanics seen this setup?
– Hide quoted text — Show quoted text -> I believe it a computer carb that was SUPPOSE to help Pollution. 87 and up > went to EFI. take that smog pump crap off, I did and seen a 16 pounds of > torque incase at the real wheels and still passed the emission. I had it put > on a dyno(did some performance tuning) > Do you have one on your 86? > And if so why? > I don’t have a computer to open and close it, so why would Chevy put one > there? > It has 2 wires that one runs to the TVS on the upper waterneck hose and > the > other goes into the firewall, underneath the dash I’m assuming? > I don’t have an O2 sensor either, so this does not make any sense to me! > And I don’t have a Check Engine Light either so the motor is not a CCC or > C4 > System. > I do have a cat, and a airpump thought and all related smog hoses! > A Hybrid maybe?!!! > Can someone explain!
Response:
> I didn’t get the entire post, but are you talking about the 2-wire plug on > the pass side front?
Yes it is, and it is supposed to be getting a signal from a small computer under the dash so I’m told. Now do you know what voltage it is suppose to send out to the mixture control valve on the carb? This is a 2-stage accelerator pump, and it’s controlled totally by temperature and vacuum controls. Temp yes, vacumn?! And where does this small computer get it’s input from? There is no O2 sensor on this motor I have the same 86 – Hide quoted text — Show quoted text -> setup in my K1500 305. It basically gives twice the "squirt" when it’s cold > to aid in cold engine operation. > Just taking that "smog pump crap" off is the worst mistake most people ever > make. Why? These setups (my 86 is a good example) are complex systems (key > word-system) that use many sensors, switches, and other things. If you take > away just one piece of the "system" you’ve pretty much rendered the whole > thing useless. What it amounts to, is either leave it alone, or take it ALL > off. And the latter is not something a non-knowledgeable person with a > "generic" Chiltons manual should be attempting. On the other hand, if you > know your stuff, feel free to alter and test, alter and test, alter and test > until you find your "happy place." > I hate it when someone just blurts out "rip it all off–it’s crap anyway" to > these newgroups. You just don’t know what kind of heartache you’re going to > cause somebody. > | I know it’s a computer carb, but where does it get it signal? > | Any CERTIFIED Chevy mechanics seen this setup? > |
– Hide quoted text — Show quoted text -> | > I believe it a computer carb that was SUPPOSE to help Pollution. 87 and > up > | > went to EFI. take that smog pump crap off, I did and seen a 16 pounds of > | > torque incase at the real wheels and still passed the emission. I had it > | put > | > on a dyno(did some performance tuning) > | > > | > > Do you have one on your 86? > | > > And if so why? > | > > I don’t have a computer to open and close it, so why would Chevy put > one > | > > there? > | > > It has 2 wires that one runs to the TVS on the upper waterneck hose > and > | > the > | > > other goes into the firewall, underneath the dash I’m assuming? > | > > I don’t have an O2 sensor either, so this does not make any sense to > me! > | > > And I don’t have a Check Engine Light either so the motor is not a CCC > | or > | > C4 > | > > System. > | > > I do have a cat, and a airpump thought and all related smog hoses! > | > > A Hybrid maybe?!!! > | > > Can someone explain! > | > > > | > > > | > > | > > | > |
Response:
I agree 100%… – Hide quoted text — Show quoted text -> Just taking that "smog pump crap" off is the worst mistake most people ever > make. Why? These setups (my 86 is a good example) are complex systems (key > word-system) that use many sensors, switches, and other things. If you take > away just one piece of the "system" you’ve pretty much rendered the whole > thing useless. What it amounts to, is either leave it alone, or take it ALL > off. And the latter is not something a non-knowledgeable person with a > "generic" Chiltons manual should be attempting. On the other hand, if you > know your stuff, feel free to alter and test, alter and test, alter and test > until you find your "happy place." > I hate it when someone just blurts out "rip it all off–it’s crap anyway" to > these newgroups. You just don’t know what kind of heartache you’re going to > cause somebody. > | I know it’s a computer carb, but where does it get it signal? > | Any CERTIFIED Chevy mechanics seen this setup? > |
– Hide quoted text — Show quoted text -> | > I believe it a computer carb that was SUPPOSE to help Pollution. 87 and > up > | > went to EFI. take that smog pump crap off, I did and seen a 16 pounds of > | > torque incase at the real wheels and still passed the emission. I had it > | put > | > on a dyno(did some performance tuning) > | > > | > > Do you have one on your 86? > | > > And if so why? > | > > I don’t have a computer to open and close it, so why would Chevy put > one > | > > there? > | > > It has 2 wires that one runs to the TVS on the upper waterneck hose > and > | > the > | > > other goes into the firewall, underneath the dash I’m assuming? > | > > I don’t have an O2 sensor either, so this does not make any sense to > me! > | > > And I don’t have a Check Engine Light either so the motor is not a CCC > | or > | > C4 > | > > System. > | > > I do have a cat, and a airpump thought and all related smog hoses! > | > > A Hybrid maybe?!!! > | > > Can someone explain! > | > > > | > > > | > > | > > | > |
Response:
I didn’t get the entire post, but are you talking about the 2-wire plug on the pass side front? This is a 2-stage accelerator pump, and it’s controlled totally by temperature and vacuum controls. I have the same 86 setup in my K1500 305. It basically gives twice the "squirt" when it’s cold to aid in cold engine operation. Just taking that "smog pump crap" off is the worst mistake most people ever make. Why? These setups (my 86 is a good example) are complex systems (key word-system) that use many sensors, switches, and other things. If you take away just one piece of the "system" you’ve pretty much rendered the whole thing useless. What it amounts to, is either leave it alone, or take it ALL off. And the latter is not something a non-knowledgeable person with a "generic" Chiltons manual should be attempting. On the other hand, if you know your stuff, feel free to alter and test, alter and test, alter and test until you find your "happy place." I hate it when someone just blurts out "rip it all off–it’s crap anyway" to these newgroups. You just don’t know what kind of heartache you’re going to cause somebody.
| I know it’s a computer carb, but where does it get it signal? | Any CERTIFIED Chevy mechanics seen this setup? | > I believe it a computer carb that was SUPPOSE to help Pollution. 87 and up | > went to EFI. take that smog pump crap off, I did and seen a 16 pounds of | > torque incase at the real wheels and still passed the emission. I had it | put | > on a dyno(did some performance tuning) | > | > > Do you have one on your 86? | > > And if so why? | > > I don’t have a computer to open and close it, so why would Chevy put one | > > there? | > > It has 2 wires that one runs to the TVS on the upper waterneck hose and | > the | > > other goes into the firewall, underneath the dash I’m assuming? | > > I don’t have an O2 sensor either, so this does not make any sense to me! | > > And I don’t have a Check Engine Light either so the motor is not a CCC | or | > C4 | > > System. | > > I do have a cat, and a airpump thought and all related smog hoses! | > > A Hybrid maybe?!!! | > > Can someone explain! | > > | > > | > | > | |
