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I just performed a pressure test on my 2000 Grand Prix SE’s fuel system and when running it achieves 44psi, which is normal. However, when I turn the engine off to do a leak down test, it loses pressure in about 5 to 10 seconds. Another bit of info from the test, the pressure reaches 55psi when you dont start the car only for a brief moment before the pressure is lost. Btw, the car runs well once it starts, but can be sluggish to start as I see the poor fuel pressure and possible air in the rail from the leak. Regulator is good, and I have no external leaks. Fuel filter is new with no restrictions. How likely is it to be a bad fuel pump check valve? I don’t think it’s a bad injector as that usually is a slow leak. Any suggestions? I don’t think this car has rubber fuel lines so I haven’t pinched off the return line yet to isolate the leak. The engine is the 3800 series 2 3.8L v6.
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Can you hook up the fuel gauge at the fuel filter location or pinch any rubber lines off
to isolate the tank from the rail? this way you can determine fuel pump or injectors. You
did pull the vac line on the fp reg to see if gas is leaking or wicking?Sounds like the fuel pump is getting weak even when the fuel pressure is good.Fuel pumps can get weak and cause performance problems.Another thing I see with fuel pump failures is this brand used: Airtex. Anyone saying Airtex fuel pumps are good are full of crap,high failure rates.AC Delco or Delphi only for a GM fuel pump replacement
I’m glad you mentioned the possibility of a weeping regulator as i know that is a notorious issue with these engines. Mine is good, pressure rises to max when i pull the intake vacuum line off of it. I have no way of putting my gauge on the line by the filter as my gauge doesn’t have all those fancy splicing adaptors like the professional gauge kits. I looked around at the fuel lines and all are either plastic or metal, so I can’t pinch them off :/. It’s a bit more work, but can’t I simply pull the fuel rail off and leave the injectors in to see if any spray fuel (not turning the engine over)? If they don’t leak visibly, then I can assume the pump assembly? Thanks for the input so far. I do agree that Airtex is crap, I was looking at a Delphi unit to potentially replace it with.
Depending on your ability you could save some money and buy just the pump. I have an 01 impala with the series 2 3.8 and that’s what I did. It’s not terribly difficult. The hardest thing to do was put the plastic flex tube in between the pump and the assembly. The rest was easy. You can find the pump on eBay.
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The fuel pumps on Ebay are cheap fuel pumps.I see a lot of problems with cheap aftermarket fuel pumps.Drop in the Delphi or AC Delco fuel pump in doing it once.Plus Delphi has a lifetime warranty on their fuel pumps.That one,you may not have to drop the tank on.There is an access plate underneath the back seat you remove.
I agree on the cheap pumps but the one I purchased was an AC delco
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Well done on checking the fuel pressure. I actually cover that exact issue in this video.
You can do 1 of 2 things. Before you crank the engine, cycle the key to the ON position a couple of times before you crank. This will prime the system and it should start fine after that. The other option is to replace the fuel pump. The reason it’s bleeding down is in this video.
Good luck and keep us posted.
Thank you all for the advice yet again :). I’ll try to throw in a new pump potentially Thursday next week as I have a jam packed week training for the local “Tour de Tonka” bicycle ride on Tuesday and working 50 hours. I’ll keep this updated on my findings.
Good news! Sorry about the super late response. I just threw in a new delphi pump today between some nasty thunderstorms and it holds pressure like it should now. Thank you all for helping me properly diagnose the issue and allow me to not waste my 35 minutes of time replacing the pump ;). It most certianly was the check valve Eric.
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