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

[Lorrin Barth]

Is there a vacuum hose routing diagram on the underside of the hood?

[Dwayne]

Yes, and I was going to throw a vacuum gauge on the engine, however I’ll do that after I replace the fpr

[college man]

seeing you have a p0300 random misfire we need to determine what
cylinder is down on power. Try doing a power balance test with the
injectors. On this motor one ignition coil fires two cylinders which
is 50% of the spark to the engine. test all 4 of the wires with a spark
tester for spark. also these ignition coils and control modules sit on
a plate which need to be clean of rust as these are your ground.

http://www.ericthecarguy.com/faq/solving-automotive-no-start-problems

http://www.ericthecarguy.com/faq/solving-automotive-performance-issues

[Lorrin Barth]

College man, what I am wondering about is the routing of the vacuum line to the fpr. The OP writes that it is connected to the intake boot. Well, where ever that is I’m wondering if it is correct.

[Dwayne]

[quote=”barneyb” post=109976]College man, what I am wondering about is the routing of the vacuum line to the fpr. The OP writes that it is connected to the intake boot. Well, where ever that is I’m wondering if it is correct.[/quote]
hi barneyb
the vacuum line to the fpr is routed correctly. The vacuum hose is on the intake boot, located between the air box that has the filter, and the plenum that goes over the TB. The engine also has the cop encapsulated inside the ignition module black box on top of the head

maybe I can find a pic and post it, here are two, note the fpr vacuum line on the intake boot just before the TB plenum that sits on top of the TB. In this configuration there is no vacuum in that line, the metered air just flows on by that line, weird! I will do some more research on why that vacuum line is even there, if it has no vacuum
[IMG]http://i494.photobucket.com/albums/rr310/buckz6319/2003_Pontiac_Sunfire_Ecotec_zpse1ea6e70.jpg[/IMG]
[IMG]http://i494.photobucket.com/albums/rr310/buckz6319/maxresdefault_zps8f25c5b6.jpg[/IMG]

[Lorrin Barth]

Clean engine compartment! Things are always changing but ordinarily the fpr samples vacuum in the manifold and adjusts fuel pressure to match changing manifold pressure. When it samples nothing why have the line? I guess we need somebody smarter than me here to explain it.

[Dwayne]

[quote=”barneyb” post=109988]Clean engine compartment! Things are always changing but ordinarily the fpr samples vacuum in the manifold and adjusts fuel pressure to match changing manifold pressure. When it samples nothing why have the line? I guess we need somebody smarter than me here to explain it.[/quote]
barneyb
yes, engineers are always changing, reconfiguring to ensure efficiency, and performance

you are correct about the fpr pulling vacuum from the manifold:) but for what ever reason this one doesn’t…idk why it’s set up this way, but I will research it. I do know I can check the fpr several ways, but since this one is already leaking, I’ll just put a new one on, then continue with my troubleshooting.

I still can’t figure out the psi rise in the system during the time it all bled out that evening, and when I got home from work the next day, there was enough psi in the system to make me scratch my head a but. I feel like the pressure in the tank after sitting all day, and it being hot out, probably caused the pressure to come back up?

[Lorrin Barth]

It can’t be pressure in the fuel tank. Fuel tanks are made of thin material and a few pounds of pressure in the tank would make it round.

[Edit]Thinking about this the obvious answer is that someone started the engine.

[Dwayne]

Well, I just changed the fpr, and the car runs better already. I’m letting it sit for a while with pressure gauge hooked up, and I’m keeping my fingers crossed that the pressure is maintained, and it doesn’t all leak out

I will report back on my findings

[Dwayne]

Okay, update…I went for a test drive for about 25 miles, some highway, some city stop n go.

I had city driving problems thus far. The car quit without warning when coming to a complete stop at traffic light, and one stop sigh. In both cases the car didn’t give any warning that it was going to cut off, it just did it.

I couldn’t here a fuel pump noise after the engine shut off, so I put it in park quickly turned key off then key on, heard the fuel pump prime, and started the engine no problem. I didn’t have any rough idle, missing, or nothing that was alerting me that she was going to quit. I did make it home:0

Now I need to move forward and continue to troubleshoot further, at least I got rid of a fire hazard, and rough idle

[Dwayne]

[quote=”college man” post=109969]seeing you have a p0300 random misfire we need to determine what
cylinder is down on power. Try doing a power balance test with the
injectors.thanks! I will do that test On this motor one ignition coil fires two cylinders which
is 50% of the spark to the engine.the ignition coils are not visible, they are encased in a long black rectangle plastic housing, and the ignition module sits on top, so I can’t find any info on how to test such a system, any info would be appreciated on this one test all 4 of the wires with a spark
tester for spark. I believe I can do this, just have to remove the coil pack for all 4 cylinders, as one unit, and put spark plugs in each boot, to test also these ignition coils and control modules sit on
a plate which need to be clean of rust as these are your ground.the coil pack is plastic, and bolts to top of rocker cover. The ignition module is a separate unit that sits in it’s own nest, and screws to the top of the long coil pack. I would appreciate any information on how to test coil resistance, and how to test the ignition module, below is a pic of a Ecotec 2.2 with this type of ignition system I’m referring to

http://www.ericthecarguy.com/faq/solving-automotive-no-start-problems

http://www.ericthecarguy.com/faq/solving-automotive-performance-issues%5B/quote%5D
[IMG]http://i494.photobucket.com/albums/rr310/buckz6319/2003_Pontiac_Sunfire_Ecotec_zpse1ea6e70.jpg[/IMG]

Now the car will start and run, with excellent vacuum according to my vacuum gauge, but it will now just quit running without warning, and I here the fuel pump relay click when it quits. To get the engine restarted I have to turn the key completely off, then back on, so it will start and run. The fuel pressure is per specs, and I have installed a new fpr. I tested the fuel pump volume today, and it will pump 1QT of gas in 30 seconds, but I could only do this test with engine running, not by just truning the key on, because the computer takes over the operation of the fuel pump after initial prime and start

[Lorrin Barth]

There was an owner posting here a few months ago concerning a Mustang that would show the thief light run rough and sometimes quit. I wrote him back saying if the thief light is coming on that means the computer is quitting – clean your grounds. Fords are known for bad grounds. He did and that fixed it.

So, anyway, lucky suggestion but something to consider.

[Dwayne]

[quote=”barneyb” post=110205]There was an owner posting here a few months ago concerning a Mustang that would show the thief light run rough and sometimes quit. I wrote him back saying if the thief light is coming on that means the computer is quitting – clean your grounds. Fords are known for bad grounds. He did and that fixed it.

So, anyway, lucky suggestion but something to consider.[/quote]
Thanks I’ll check into that
But theft light on when it just quits
It just quits lol

[Stephen Bowen]

I’m going to go out on a limb–as this issue is one that the VW’s I work with also share.

It’s caused a lot on those cars by a defective crank sensor. Could also be a cam sensor as well on some engines. I’m not sure on yours, just floating it as a possible issue.

I’d check the grounds–as that’s very possible– And I’d also look into testing the crank and/or cam sensor- Which ever one this car uses for the engine RPM. If the sensor is easy to get to? Maybe having the car just sit there at idle and give the sensor a very light ‘tap’ with the butt end of a screw driver?

S-

edit: at times if the sensor is vibrated just right it can drop the signal to the computer. If the computer sees the engine has no RPM? Then it will throw the system into ‘shut down’. as in–no fuel pump or ignition. It thinks the engine stalled out. Tapping the sensor with a screwdriver handle can cause the issue to happen on ‘command’ if it’s bad enough.

I’m only throwing it out there, as I am not sure about your system.

[Lorrin Barth]

Is a bad suggestion better than no suggestion at all – lol.

[Author]

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