When the truck has been sitting a while, such as a couple of hours or half a day it is exhibiting the following problem: I turn the ignition on and it rolls the motor over and will not start the engine. I let off the ignition and then it starts right up.
Any one have any ideas where to start?
Thanks
Try this, turn the ignition on for 10 seconds and then off again for 5 seconds and then on again for 5 seconds, then start the engine. If the engine starts, your fuel pressure check valve on the fuel sending unit "Fuel pump" has gone bad and will cost you a new fuel sending unit or you learn to pressurize your fuel line as mentioned above. The valve is on low pressure return line on the fuel sending unit, the other place where fuel could be leaking is form your fuel pressure regulator, but what you have described does not indicate a bad fuel pressure regulator.
Here is a test you can do:
* Check cold start fuel pressure.
* Check engine running fuel pressure.
* Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
The 75-85 is only a check on the capable full pressure of fuel pump.
If you can not find the rubber return line check full pressure by plugging return line or just or the true full pressure can be taken direct at the end fuel filter.
* What are the pressure readings that you have done.
* What are your cold start pressure readings?
* Post back what you have.
