Strange things happening with fuel pressure…

[Dwayne]

I’m currently working on a car for a customer, that has strange things happening with fuel pressure…

Vehicle is a 2004 Chevrolet Cavalier with Ecotec 2.2 automatic 117,000 ish miles

I have repaired numerous issues with this car over the last few monthe, and now there is another issue that need to be resolved. I’m no professional auto tech, but I Lovetowrenchit!, So here we go…

Complaint
1. engine will run rough at idle sometimes, engine will run smooth sometimes, engine will be hard to start sometimes, engine will quit running sometimes, engine will shut off sometimes when cornering, leaning ect.

2. CEL comes on sometimes.

3. I take a chance on driving the car, never know when it will quit running, and if it does…It will be hard to restart, but it can be restarted, and will run

What I have done after work hours, and what my finding are. I’m suspecting a fuel issue of some sort

1. Pulled trouble stored trouble code, cam back P0300..YUCK!! I know I’m in for a real fun time with this one Lol

2. Hooked up my fuel pressure tester, tested fuel pump for pressure KOEO got 60psi, Okay, good!

3. I decided to see if she will have a problem starting and running, fired right up, and ran smooth and without any misfire…Good:) while running fuel pressure dropped down to 57psi Good!…

4. After about 20 minute of no evidence of the initial complaint. I shut the engine down, and watched the fuel pressure needle. It dropped from 57psi down into low 50’s, but over a period of time, about 1 hour the pressure was down to low 40’S, after several more hours, pressure down to the 30″s, let the car sit over night, got up to go to work the next morning, checked the pressure gauge…it was ” 0 ” psi.

This is where it gets weird. I went to work that day, came home 12 hours later, looked at the fuel pressure gauge, and somehow the pressure went back up to the 30 ish psi range. Well i didn’t expect that Lol..now I’m scratching my head trying to figure out what is going on…

5. I decided to do a fuel pump volume test KOEO and got around 1 Qt in about 40sec..Good!
don’t think the fuel volume is a problem…maybe the fuel pump check ball is leaking, slowly…still a possibility

6. I got to thinking maybe a vacuum leak, fuel pump pressure regulator issue, leaking injector, or injectors. Well before I could start figuring out which way to go with my troubleshooting, I smelled fuel. I spotted some fuel on the outside of the fuel pressure regulator where it is mated together, and thought how could that be happening??

Well, I don’t have any fuel in the vacuum line, and the vacuum line is hooked to the intake boot, and not on the manifold, so no vacuum at idle on that hose. I’m not sure if if it has any vacuum at all on that hose. I pulled that line off the fuel pressure regulator while engine was running, for about 10 minutes or so, and no fuel pushed out of the regulator.

7. I’m going to purchase a new fuel pump regulator tomorrow, not sure if it is causing the pressure bleed off, because when I pinch the return hose I get pressure increase of 10 psi or so, that seems normal to me from what I know.

I am purchasing the regulator tomorrow to take away a fire hazard, and hoping that the diagram inside has a small rupture, and all this troubleshooting will end, without me going to troubleshoot the fuel pump…

I would appreciate any help/direction on which way to go. I don’t want to drop the tank unless I need to, and want to keep the cost as low as possible, for my buddy

thanks for taking the time to read this, I appreciate it:)

Topic

[EricTheCarGuy]

You’re most welcome. That’s what I’m hear for. Thanks for the updates and for using our little forum.

[Author]

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