chevyaurora

2007 Chevy Silverado Classic has an intermittent no start issue. The truck cranks, starts then shuts off. When this happens there are no gauge warning lights when the key is in the on position. Please see attached video for the issue.


Parts I have changed:

ignition cylinder
ignition switch
BCM
PCM
checked all grounds for clean connections
ignition fuse

chem_man

Have you checked your fuel pressure - both when it normally starts and then when it does not start?

chevyaurora

I am going to check my fuel pressure later today. I will let you know the readings.

chevyaurora

I checked the fuel pressure. I hooked up the fuel pressure gauge and turned the key to the on position. The pressure read 55 psi then slowly moved down to 30 psi after 5 minutes. Does this sound normal?

chem_man

Something is definitely wrong. First, the fuel pressure specification for your vehicle is 56 - 62 PSI, so 55 PSI is below the lowest specified fuel pressure. Secondly, it should hold pressure right around 55 PSI for more than 5 minutes. So, what does this all mean? Well, it looks like your fuel pump is wearing out since it does not reach the minimum factory specified pressure. Also, the reason for the rapid drop in fuel pressure with the engine off needs to be determined. It could be the check valve in the fuel pump assembly is worn and the pressure is bleeding off due to that, OR, one or more of your fuel injectors is leaky.

The easiest way to check for a leaky fuel injector is to let the fuel pump cycle a couple of times over 10 to 15 minutes (just turn the key to the on position without starting the engine for about 5 seconds to let the fuel pump turn on and get up to pressure then turn the key to the off position - repeat again in 5 to 10 minutes) and then pull the spark plugs and check to see if the electrode area of the spark plug is wet with fuel. Wet plugs can indicate an injector that is not sealing shut when the power is removed from it. Another method is to pull the injector rails while leaving the fuel lines connected to them, cycle the fuel pump a few times and then look for gas dripping from one or more of the injectors.

In addition to that, if you have a flex-fuel engine, the sensor used to determine the amount of alcohol in the fuel might need to be reset, and the best way to do that is to let a dealership do it and while they are at it they can apply any updates to the PCM. From what I have read on the various forums, most dealerships charge about an hour of labor time to do this.

Now, if you decide to replace the fuel pump yourself, please do not try and save some money by purchasing a low priced, no name fuel pump off the internet. You will come to regret it in all likelihood. Please purchase either an ACDelco or a Delphi fuel pump. They are the best and will likely last for many, many years. While every now and then one can get a defective fuel pump from ACDelco or Delphi, they do stand behind their pumps with a lifetime warranty.

Good Luck!

chevyaurora

Thank you for the detailed response verifying that there is an issue with the fuel pressure. I have already cycled the fuel pump with the key on and off for 15 minutes in my recent troubleshooting methods. There were no signs of leaking injectors or the smell of fuel in the engine compartment. I also changed the plugs and wires last week and the plugs were dry with no fuel or oil residue. Three weeks ago, I changed out the knock sensors which required pulling off the intake manifold. Everything on top of and along the head were clean and dry. All parts (spark plugs, spark plug wires, knock sensors and knock sensors harness) were replaced with ACDelco. This is not flex fuel so we can rule this out.

Is the rapid drop in fuel pressure causing the truck to start for one second then shut down? I am inclined to change the fuel pump to solve the issue.

This still doesn't explain the gauge warning lights not firing up when they is in the on position. Any thoughts on that? When they do fire up when the key is in the on position, then the truck will start and run every time. This is the thing that is throwing me off.

tech2

theft light on?

chevyaurora

Theft light is not on or is not blinking.

chem_man

I think what Tech2 is asking about has to do with the Passkey anti-theft system, and if it is causing the intermittent no start condition.

What you are looking at is a chicken or the egg problem. Is the fuel system causing the intermittent no start condition because the fuel pump is bad, or is the fuel pump responding to something else telling the engine to shut off.

What is your fuel pressure with the engine running?