Hooked up a fuel pressure tester between the fuel filter and the FPR. Did the first test from the FSM (hold pressure inspection) came up 16 psi (should be 18psi) after 5 min. Then did the 'Fuel line pressure inspection', resulting in 42 psi (should be 34.1-39.8psi)while the car is on with the fuel pump going. Per the FSM, this means bad FPR, correct? Just wanted a second opinion, and wasn't sure if 2 psi difference would cause so many problems.

The main issue is a very rough cold start (have to pump the gas petal to get it started while cranking, then idles like crap and backfires until warm) and stumbles in higher rpms. Hot start has been a minor issue for a while now, I have to rev the gas to keep the rpm's up.

 

I wrote a mistake here. Ignore.

By the way, the 42 isn't all that far from 39psi imho. I'd check the pressure at idle also. It's not uncommon for me to see around 31-32psi at idle, even though the FSM says, what? 28psi?

 

32 at idle, FSM says 27-33.
I just noticed something when I just started it up, it shook violently for the first few seconds this time, but the cold start actually kicked in and kept the rpm's up to 3k, first time that has happened since it started running so bad.

 

what is the fuel pressure with the engine off, key in the on position, and fuel pump check connector jumpered? That is, base fuel pressure when the engine is not under vacuum.

 

Stock fuel pump?


-Ted

 

42psi

Yeah, stock pump.

 

I thought base fuel pressure on the stock regulator was like 36-38, that's at 0psi atmospheric pressure like I described. Could be a bad FPR if you say you have at stock fuel pump.

 

34.1-39.8 is the norm. I wouldn't think 2psi would make it run so terribly.

 

Here's some jpg of fuel rail pressure. First pic is for a Turbo at idle (750rpm). The next pic is a Turbo with just key ON, engine OFF.

The next two pic are the same condition but on a non turbo engine.

Anyway, with the turbo engine running I pinched the return line to get the fuel pressure above 32.2 at idle. I pinched it to get 40psi and plus. Sorry, the idle didn't do anything *funny* and still idled fine. Sorry 'bout that.

I also used a mechanical gauge on the non turbo and the figures are not that different from using a Fluke digital meter with a Fluke PV350 transducer attached to it. The only pic with the mechanical gauge is of a non turbo engine with key ON, engine OFF.

To me, the crummy running of your engine isn't a fuel pump problem.

There is one thing you might do that you might not have. See what the dead head pressure of the pump is. I forget if you did that or not. Supposed to be in the eightys give or take. I forget right now.

 

Here's the non turbo idling using a mechanical gauge. DONE

EDIT: And as a side thought, I've always been dead set against pinching fuel injector fuel lines. I really don't abide with doing that ever.

EDIT: the last pic is the fuel rail pressure after the turbo engine had been turned off for over twenty minutes. Seems the check valve in the fuel pump is a workin ok.

EDIT AGAIN: And if you noiticed, the Fluke shows PSI as a MV display. It's not millivolts but psi being displayed.

 

Wow, thanks for all the info and tests. I still plan on dead head testing the fuel pump just in case, but I'm also starting to doubt it's the pump. Do you think it may be the pressure regulator? The difference of psi in your two tests (idle, and key 'on') is about 6, mine is 10.

 

Any other ideas?
Cliffs: changed spark plugs and wires, drove it a few hundred miles, next day starts and idles like crap, backfires, and sluggish while driving.
Could it be timing maybe?

 

Backfire would indicate unburnt fuel. I think you've got a spark problem, despite the recent tune up. Do you have a timing light? I'd look to see if each plug is firing consistently.

 

Not really. You missed the part where I said I had the engine idling and made theh fuel pressure at idle rise by getting a pair of pliers and pinching the Return line on the engine to make the fuel pressure rise at idle from 28-32 psi to forty plus. The engine kept idling with no crummy effects with the pressure at forty.

IF you have a spare FPR, by all means change it out to see what happens. I would check the deadhead pump pressure to make sure it gets up there in the 70-90psi range (whatever the FSM says it should be is what I mean).

RETED asked if this is a stock fuel pump or not. A Waldo pump might cause the pressure to read a bit high because the FPR can't adjust for the extra pressure/volume.

Timing could be the problem.

Not to insult, but getting the plug wires on wrong could be the problem. The Lead wires go on the bottom and it does NOT matter which of them go to which lower plug since they fire at the same time. But if you get the Trail plugs swapped around assbackwards, the engine will run real crummy. Or if you put the Lead wires on bottom and trail on top will make the engine run crummy. Real crummy.

Trail plugs not even on the engine will not make the engine run bad and you won't even notice it but for the tach not working at all.

Busted apex seals make motors run crummy.

AFM's which have been opened and fooled around with will cause the engine to run crummy. If the engine has been running ok and just now went bad, then that isn't a possibility if you have not messed with its internals.

 

Ok, tried pinching the return line while idling at about 850. Pressure went up to about 45psi, and the idle dropped and the car almost stalled. When I tried a few seconds later, it did nothing when I pinched the line, no rise in pressure, no weakening idle. I waited a few minutes and was able to raise the pressure and drop the idle.
Don't know if that means anything, but I'm going to try the dead head test to the fuel pump now.

And yeah, I've checked the plugs multiple times, that was the first thing I thought was wrong.

Pump pressure is 64 psi.
Hhm, thats low isn't it...

 

71-94 for a non turbo car. Might try changing the fuel filter. I don't think a couple of psi low is causing the car to backfire, idle bad and be sluggish when driving nor a couple of psi high in the rail would cause your problem.

A clogged fuel filter might do one of those.

I'd be looking at timing or a fooled with afm or the like for the problem. Sparkplug wires on right? REmove the Trail plug wires or disable the Trail coil and see if it drives different. Maybe a compression check also.

 

Maybe a disconnected or bad thermosensor? It would account for the lousy cold engine issues. Although, that would not account for the hot start issue and the high rpm. Bad injector?

 

Haven't touched the AFM.
Took off the trailing coil pack and took it for a spin, actually started and ran better than before. Is the coil pack my problem? Or timing?
Thanks.
BTW, already tested the thermo sensor, and changed the fuel filter about 5 months ago.