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5.7L 1500 won't start after being driven and shut off

41K views 19 replies 12 participants last post by  realunion 
#1 ·
I have a 5.7L 1500 GMC Sierra that has lately decided to strand me at random locations throughout my hometown. I get in in the morning, crank, and it goes. I stop to do anything, hop back in, and I can crank it all I want and it will not fire back up. Fuel pump is running it's little heart out, starter is trying its hardest, but the truck just will not fire up till it damn well feels like it. I've already replaced both the cam and crank sensors, new fuel pump and filter as of 3 months ago, and new wires and plugs as of 2 months ago. I'm beginning to get a little stressed. I'm sure this topic has been posted before, I just didn't have the time to browse all of them. Any help is appreciated. Greatly.
 
#4 ·
I can't remember which type of fuel injectors your vehicle has. Try running a tank of Shell premium fuel through it. That fuel has excellent cleaning qualities and you don't have to mix anything. Just pump it in.
Then after they get cleaned you can re-evaluate.
 
#5 ·
Wife's Car had a problem like this it wound up being her ignition coil and control module but that is a little Saturn 4 banger not a chevy V8 . . . have a check engine light on? get an auto store to read the code?
 
#6 ·
I am fairly interested in theories myself because my Corvette is doing the same thing. Difference is it is a 1988. My ideas all lead to the same road of bonked injectors spacifically something to do with heat soak and blah blah blah. Problem is what is the blah blah blah part? I have run every cleaner known to man. Is your problem worse if the engine gets up to full engine temperature? Is the problem proportional to the time left off? (ie if your kill it for 30 seconds can you get it to turn back on?)
 
#7 ·
Sounds like an ignition module to me.
 
#10 ·
lzn197 said:
AzDragonLord said:
Sounds like it's vapor-locked to me.
Huh? Explain this please?
Vapor lock occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient loss of power or complete stalling. Restarting the engine from this state may be difficult. The fuel can vaporise due to being heated by the engine, by the local climate or due to a lower boiling point at high altitude. A vapor lock is more likely to develop when the vehicle is in traffic because the under-hood temperature tends to rise. A vapor lock can also develop when the engine is stopped while hot and the vehicle is parked for a short period. The fuel in the line near the engine does not move and can thus heat up sufficiently to form a vapor lock. The problem is more likely in hot weather or high altitude.
 
#12 ·
I had the same problem. It also started idling high and sometimes wouldn't shift into overdrive. Was running 2500 rpm at 55 mph. Check engine light was on and code said low coolant temp. Changed the thermostat but still the same. New fuel pump didn't fix it either. Saw on another post the coolant temp sensor could cause it. Didn't think that was the problem but changed it anyway. Problem fixed. Wish I would have done that before changing the fuel pump!
 
#13 ·
Have u tried flooring the gas pedal while cranking? I have excatly the same problem. My gmc also sometimes stall when idle. Cant seem to figure out the problem. I dont know if its fuel related. Could also be some kind of ignition problem, but that doesnt explain why it fires up easy when cold. I think ill try to insulate the fuel pipes behind the engine.
 
#16 ·
gmctruckguy said:
Sounds like an ignition module to me.
OP, i would have to agree with "gmctruckguy"

Had an Impala SS the same year as your truck. Had a similar problem to what your experiencing and the ICM was the cause. It was cracked when i replace it. Not sure if it was heat or what have you but replacing the ICM did the trick. They are fairly cheap too, i believe.
 
#18 ·
Yeap. ICM = Ignition control module

I'm not going to speculate on the details of your problem. All i can tell you is that I owned a 96 Impala SS from roughly 150k to 240k (7yrs) and i dealt with a host of issues, both fuel and ignition related. I had an issue simular to yours (intermitent strarting issue) relatively early in my ownership with the Impala. It was recommeded to me by a friend of mine (quality mechanic) to swap out the ignition coil and ignition control module. Upon replacing both I realized the ICM was cracked. Car fired right up and no further issues after i swapped the before mentioned ignition parts. If you give the ICM a shot, remember not to over tighten the mounting bolts and use di-electric grease. That part is flat/skinny and IMO, a little on the frail side. Hope this helps....
 
#20 ·
If gm vehicle wont start try disconnecting battery to reset computer.I used an old key pod and the computer went crazy.my vehicle had great difficulty starting an fan would run all the time and computer was saying my engine was hot and turned off air conditioning.If you have these problems reset computer first before replacing say ignition control module etc.I will have to get old key pod reprogrammed or get another made.
 
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