Won't start hot - 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, ...

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.

You say the starter is trying it's hardest. Is it cranking over real slow? Or cranking over like normal speed but doesn't fire up?

Seems to be at normal speed. It just feels like it could start at any second, but doesn't. Just about the most aggravating problem I've encountered yet.

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.

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?

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?)

Sounds like an ignition module to me.

Sounds like it's vapor-locked to me.

AzDragonLord wrote:Sounds like it's vapor-locked to me.

Huh? Explain this please?

lzn197 wrote:

AzDragonLord wrote: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.