2000 sonoma starting issue

[sonoma00]

I have 2000 sonoma with 4.3 with the CSEFI and it takes a while to start after it sits for awhile and it is really doggy for about 1/4 mile then runs just fine. Fuel pressure is 55-60 while running and as soon I shut it off it drops to nothing and you can hear fuel dumping back into tank. I've been told it is the fuel pressure regulator, but before digging into that I want to if it be something else.

Any help would be great

 

[Molson02536]

I have 2000 sonoma with 4.3 with the CSEFI and it takes a while to start after it sits for awhile and it is really doggy for about 1/4 mile then runs just fine. Fuel pressure is 55-60 while running and as soon I shut it off it drops to nothing and you can hear fuel dumping back into tank. I've been told it is the fuel pressure regulator, but before digging into that I want to if it be something else.

Any help would be great

If it's not your fuel pressure regulator, it's your CSFI poppet valve that has gone bad with carbon build up at the poppet. There is a check valve at the fuel sending unit that keeps the fuel system pressurized. You can check that by pinching off the return fuel line and then pressurize the fuel system, you should get a reading of 75 PSI (this only ensures your fuel pump is good).

Once you turn the ignition off, the fuel pressure should not drop fast. If the fuel pressure drops, your fuel pressure regulator is leaking and will need to be replaced. If the fuel pressure does not drop fast until you let the fuel back return to the fuel by un pinching the return line, then it's the check valve in the fuel sending unit that has gone bad.

Good luck and keep us posted and most of the time the "service engine soon" light will come on due to the engine running rich from the extra gas leaking in to your intake ports, but may not if the leak is not bad enough to cause it to run rich. Check all your vacuum lines to make sure there are no leaks, your fuel pressure regulator is controlled by vacuum line.

Keep us posted and good luck.