97 GMC fuel pump problem – stalling
Question:
– Hide quoted text — Show quoted text -> My 97 GMC Sierra 1500 pickup stalls or fails to start sometimes. I >just had the fuel pump replaced and that did not fix it. I believe the >mechanics at the dealership may have taken a guess and replaced the >pump without knowing for sure if it was bad. I do know that when it >stalls the fuel pump relay has dropped out. Does anyone have a wiring >diagram for the fuel pump and fuel pump relay? The pump only runs a >few seconds, then the relay drops out when I turn the key on without >starting the engine. This makes me wonder what controls the relay. >Perhaps a pressure switch? Any help would be greatly appreciated. >– >Stuart > Stuart … > The fuel pump only runs a couple of seconds to pressurize the system > if you turn the key to ON but not START. The system should probably > build to 9-13 psi (it might take a couple of ON OFF ON cycles to get > the pressure there. If it can start, it should be the 9-13 psi. > as you probably know this could be fuel or electrical. if fuel you > have the computers to contentd with, and the fuel injector could be > bad, or the ecm or the pressure regualtor or the … sorta makes you > wish for carb and diaphram fuel pump eh ? > Did the mechanics check the fuel pressure ? usually just after the > inline filter. Did they replace the filter ? Little stuff but one > can’t assume the filter is good since the truck is only a few years > old. (I doubt if it’s the filter :^) ) > replacing the pump without knowing sounds expensive but common. > any error codes ? > I don’t have a 97 manual and am just going by what I found out from a > older TBI unit and the inerlocking of the ECM, MAP, TBI, > mic,key,mo,use :^) > good luck > - Ed > —
Thanks Ed for your advice. I did not get a chance to talk to the mechanic after he replaced the pump, so I don’t know about the error codes. The truck only has 21,000 miles, so the filter is quite unlikely to be the problem. I am starting to question the fuel pump relay, which gets very warm when it the engine is running. Maybe the coil is opening up when it gets hot. I found a book with a "typical wiring diagram" for GMC/Chevy trucks, so I now have some idea what to look for. I am an electronics tech by trade. I ran the truck for 2 hours tonight, waiting for it to stall so that I might see the problem, but it ran flawlessly. Damn. And yes, it does make me wish for the days when we were still using carbs and diaphram pumps, which was a kinder, gentler time. On the other hand, we now have cars that will idle properly. And that in itself is a big step up. Stuart Before you buy.
Response:
On the GM engines, the fuel pump is controlled through the oil pressure sending switch. Check to see if the oil pressure is erratic when the stalling happens, if possible. When the computer senses no oil pressure, it shuts down the fuel system to ’save’ the engine. Bill
– Hide quoted text — Show quoted text -> My 97 GMC Sierra 1500 pickup stalls or fails to start sometimes. I > just had the fuel pump replaced and that did not fix it. I believe the > mechanics at the dealership may have taken a guess and replaced the > pump without knowing for sure if it was bad. I do know that when it > stalls the fuel pump relay has dropped out. Does anyone have a wiring > diagram for the fuel pump and fuel pump relay? The pump only runs a > few seconds, then the relay drops out when I turn the key on without > starting the engine. This makes me wonder what controls the relay. > Perhaps a pressure switch? Any help would be greatly appreciated. > — > Stuart > Before you buy.
Response:
> My 97 GMC Sierra 1500 pickup stalls or fails to start sometimes. I >just had the fuel pump replaced and that did not fix it. I believe the >mechanics at the dealership may have taken a guess and replaced the >pump without knowing for sure if it was bad. I do know that when it >stalls the fuel pump relay has dropped out. Does anyone have a wiring >diagram for the fuel pump and fuel pump relay? The pump only runs a >few seconds, then the relay drops out when I turn the key on without >starting the engine. This makes me wonder what controls the relay. >Perhaps a pressure switch? Any help would be greatly appreciated. >– >Stuart
Stuart … The fuel pump only runs a couple of seconds to pressurize the system if you turn the key to ON but not START. The system should probably build to 9-13 psi (it might take a couple of ON OFF ON cycles to get the pressure there. If it can start, it should be the 9-13 psi. as you probably know this could be fuel or electrical. if fuel you have the computers to contentd with, and the fuel injector could be bad, or the ecm or the pressure regualtor or the … sorta makes you wish for carb and diaphram fuel pump eh ? Did the mechanics check the fuel pressure ? usually just after the inline filter. Did they replace the filter ? Little stuff but one can’t assume the filter is good since the truck is only a few years old. (I doubt if it’s the filter :^) ) replacing the pump without knowing sounds expensive but common. any error codes ? I don’t have a 97 manual and am just going by what I found out from a older TBI unit and the inerlocking of the ECM, MAP, TBI, mic,key,mo,use :^) good luck – Ed — link to 100 current SE NOS/DMA charts for $8/per over 100 out of date $4/per all unmarked, unused http://www.Charts-USA.com (Lake Champlain & FL Keys digital charts)
Response:
My 97 GMC Sierra 1500 pickup stalls or fails to start sometimes. I just had the fuel pump replaced and that did not fix it. I believe the mechanics at the dealership may have taken a guess and replaced the pump without knowing for sure if it was bad. I do know that when it stalls the fuel pump relay has dropped out. Does anyone have a wiring diagram for the fuel pump and fuel pump relay? The pump only runs a few seconds, then the relay drops out when I turn the key on without starting the engine. This makes me wonder what controls the relay. Perhaps a pressure switch? Any help would be greatly appreciated. — Stuart Before you buy.
