Hot Start Problem - F.I. - 2002 GMC Sierra 6.0L

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Jim 5

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I'm trying to help my father in law with his truck.

He says that when it is at full operating temperature, to restart it the truck will crank and crank with no start. Turn the key off and turn it back on again and it starts right up.

No drivability issues whatsoever. There's a guy on the dieselplace.com forums who has the exact same issue and can't diagnose it either. He has:

- replaced fuel filter/pump
- fuel pressure regulator
- spark plugs

He says he doesn't smell fuel in the oil. I sort of suspect a leaky injector or fuel flowing back through the fuel pump and depressurizing the fuel rail.

What I don't get is why it would start fine cold or and right after turning the key off after a long stretch of cranking.

The truck throws no codes.

Can anyone give me some ideas for troubleshooting?
 
Got the exact same problem with my 2002 Cavalier. It's apparently a problem with the placement of the starter common to GM's - they get 'heat soaked' easily, and are hard to start hot.

I'll try to find a thread I had on it recently.....
 
Not sure if I get that. The starter is functioning normally, but the engine won't start. It's like someone disconnected the distributor (if this vehicle had one). The engine is cranking over but won't start until you turn it off and then turn it on again and retry.

Are you talking about the starter solenoid (attached to the starter) overheating? I know that many gm guys will buy a ford starter solenoid and relocate it up by the battery to solve this probem.
 
Had this exact problem on my 94 pontiac!

Never could figure it out.

Good luck man.
 
Mine does both - cranks 'normally' w/o starting, and sometimes 'seizes' briefly and won't crank. It just seems to be that different parts get heat soaked, and have trouble.

I'm sorry, beyond that I don't know whatt he answer is 'cause I've never tried to really fix the problem, I just live with it.....
 
A very short spray of ether as close to the throttle plate as possible can help determine if there is a fuel delivery problem.
 
Electronics can get finicky when hot. This normally isn't a problem because they are designed to with stand the heat of the engine bay, but when they start to degrade and get to the end of there life they become more susceptible.


An off the wall guess that really I have no idea if this is possible of not but something like the fuel pump relay. when you turn the key back to off it gets powered down and when you turn the key back to on it sends power to it again.
 
Cleaning the throttle body might help, and changine PCV valve. Does this engine have throttle by wire, I can't remember? The apeture around the throttle is very tight and deposits can block the airflow too much especially in hot start. Usually they will start hard though.

Make sure the fuel pump soleniod kicks on and the pump runs for 2 seconds when the key is turned to RUN, and that there's good fuel pressure.

This truck probably has PassLock II and the ignition switch has to send the right code on to the BCM and then to the PCM before the fuel injectors are enabled. I doubt there's a problem there, but if there was a trouble code set it may not light the service engine soon light. And you need a dealer level scanner to pull the BCM codes.

You want to look for what the truck is missing when it won't hart start-spark, fuel pressure, injector signal.
 
Last edited:
Originally Posted By: EricF
sounds more like iffy ignition module or relay.
my money's on the module.


I know what you're talking about. I upgraded the 302 on my Bronco to a hall effect distributor with an ignition module. Every once and a while when the truck heated up I could be cruising down the road and the truck would just stop as if someone reached over and turned off the key. A new junkyard module would solve the problem.

Since I don't want to get stranded in the boonies in my trail rig, I keep 2 spare tested modules in my tool kit.

Would a 2002 model year truck have the same type of "module"? I thought the engine management computer works or doesn't work.
 
What throws me here is that the vehicle will start right up when the key is first put to the off position.
If this fixes it, it sure is odd.
It's fuel or spark, though.
The starting fluid will show if it's a fuel problem. If you spray it and she starts right up for a few seconds, you now know what half to dive into.
 
Originally Posted By: mechtech2
What throws me here is that the vehicle will start right up when the key is first put to the off position.
If this fixes it, it sure is odd.
It's fuel or spark, though.
The starting fluid will show if it's a fuel problem. If you spray it and she starts right up for a few seconds, you now know what half to dive into.


Good tip. Thanks. Could I do the same thing with propane/butane? I've got tons of that handy.
 
Starting fluid is a sure thing.
Go ahead and try the gas, however. It should work OK. It has very high octane, and starting fluid is low. You'll have to crank as you allow the propane to be ingested.
If she fires up for a few seconds, you know it is a fuel problem.
No results probably means the ignition is at fault, so check for spark right away.
 
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