02 Fuel Pressure

[Smith1000]

When fuel pressure bleeds down, is this a problem with the fuel pressure regulator, or the fuel pump? I have replaced the fuel pressure regulator and the crank and cam position sensors. It starts good when cold, but will not start well after sitting for about 15 minutes. Have to crank on it some. If I shut it off and start it right back up, it starts well though.

Checked the fuel pressure running and it is 49 lbs. This is not an Ultra.

I replaced the regulator because there was a gas odor. It seemed like the starting issue started about that time, so it may be the new regulator, or possibly the fuel pump.

[Tech II]

Only way to know for sure, is to install Special GM tools( shut off valves on the supply and return lines.......

Cycle the ignition 3X's to get max pressure.......if pressure drops, repressurize to max, and then close both valves.....if pressure stops dropping, open return line valve......if pressure drops, bad regulator......if pressure doesn't drop, open supply line valve....if it drops, bad check valve in pump/leaking supply line/etc.

If you close both valves and pressure still drops, leaking injector....

[Smith1000]

Very helpful. Thanks. Sounds like some basic plumbing checks. I am wondering if i could detect the leak down using s stethoscope after shutting it off, or by checking the temperature of the lines for a difference.

[HotZ28]

I am wondering if i could detect the leak down using s stethoscope after shutting it off, or by checking the temperature of the lines for a difference.

No, neither one would be an accurate method of testing for a small leak.

[Smith1000]

I put the old regulator back in and this seems to have solved the hard starting issue. I believe that the small o ring seal that sits in the bottom of the housing was misaligned as it appeared slightly crimped. Has been starting well since though.