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Fuel Pressure Regulator


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9 replies to this topic

#1 Markus

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Posted 02 May 2004 - 05:08 PM

If you read my other thread ('90 Legacy Loping Idle) my current issue is with a crappy idle.

Well I have replaced plugs, wires, knock sensor, fuel filter; cleaned IAC; checked PVC valve, TPS, coil spark; listened to injectors clicking and pulled the fuel pump this afternoon thinking maybe there was some crap sucked onto the pickup screen.....no luck? It runs the same after re-installing the pump as the screen was clean.

I think it is probably the fuel pressure regulator. At idle when I pull off the vacuum hose....no change in engine speed or sound at all, when I pull off at higher rpms (2000+) just the slightest change...maybe a little faster but very slight. There is vacuum on the line as it sucks my finger against to opening.

Seems like a bad fuel pressure regulator? I'd rather just buy the part than a fuel pressure gage and then the part. What else could the problem be?

Thanks for any input.

#2 Legacy777

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Posted 03 May 2004 - 07:48 AM

before you say it's your fpr, get a gauge and test the pressure.

You will most likely not see a change in how the car runs by just taking the vacuum off the fpr, or at least I didn't when I did mine. I ran a gauge to the fuel lines and everything was good and working the way it was supposed to.

#3 Markus

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Posted 03 May 2004 - 09:16 PM

Your right Josh. I thought about it today and I would be a bit upset if my fpr was good and the fuel pump slowly dying.

It sure would be nice if that was the fix.....looks easy to get to.

I thought I had read some where that someone had pulled the vacuum hose and the rpms went way up.

Gonna go out a buy a pressure gage and find out for sure.

#4 frag

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Posted 04 May 2004 - 06:59 AM

An idea that might interest you.
I installed on both my former Loyale and my present 96 Legacy an inline fuel pressure gauge made to tap directly in the fuel line (between fuel filter and fuel rail). It's small, sturdy (brass and stainless), cheap (made by VDO and cost me 25$ CAn) and needs only a T fitting to tap into the fuel line). Since it stays under the hood, you have no problems with pressurized fuel lines going into the car and the next time you have a problem, just opening the hood will let you know if you have fuel pressure. Might even cost lest than a test fuel pressure gauge and will keep on informing you about the health of your fuel system till you part with the car. Easy to remove and keep for the next car.
Just an idea.
While i'm at it, people should not think that removing the gas cap releives the pressure in fuel lines. It does nothing of the sort, trust my fuel pressure gauge. Waiting overnight or at least 3 to 4 hours will get rid of residual pressure though.

#5 Markus

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Posted 05 May 2004 - 09:28 PM

I was wondering if there was something like that available. Where did you buy it...at a chain auto store? Autozone has the test type that I really don't need.... but a permanent under hood would be cool.

Gonna look around.

#6 frag

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Posted 06 May 2004 - 08:05 AM

I got it at Canadian Tire which is one of the biggest chain auto store in Canada, maybe the equivalent of Autozone in the US.
You could try to find a store that sells the VDO line of gauges and ask to look in their catalogue.
Better still, go have a look here.
Click on VDO at the top of the page and you'll find it in the midlle of the next one. It's called a «mini pressure gauge».
I have the 60 psi chrome one.
Good luck!

#7 Markus

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Posted 23 May 2004 - 08:33 PM

I finally got the fuel pressure gage installed today. I got the chrome VDO but got the 100 psi cause I thought I read the pressure during testing would go up to 70 psi.

The reason I got this was cause I suspected the FPR. At idle the the pressure is 30 psi. With the vacuum hose off the FPR the pressure is 38 psi. Both are in spec. So...I don't have low pressure. The Haynes book says "if you pressure is too low....do the pinch off test." I do this, even though my pressure is ok at idle, and my pressure jumps immediately to 70 psi for the short time I have it pinched.

I need help interpreting the Haynes Manual. Does this 70 psi pinch off pressure mean the FPR is bad no matter what the idle pressure is OR should I just not have done this test because my idle pressure is ok?

Any thoughts?

#8 Legacy777

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Posted 24 May 2004 - 07:47 AM

which line are you pinching off? The return line?

#9 frag

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Posted 24 May 2004 - 08:38 AM

30psi with the vac hose on and 38 psi with the hose off means your FPR is pefect. Getting the vac hose off replicates the vac condition you have when you open the throttle (no vac or less vac), a situation where higher fuel pressure is required
When you pinch the line downstream from the VDO gauge, you in fact take the FPR out of the equation and you're then testing your pump. your pump also seems to be in very good condition.
Seems your problem is not fuel pressure related.
Good luck with the rest of your testing.
P.-S.: a side benefit of having the VDO gauge is you can also monitor the condition of the rest of your fuel system. If the pressure does'nt hold steady for at lest 15 minutes after shutting down the engine, it means your FPR or your injectors or your fuel lines are leaking. If in doubt which one I think Haynes outlines the test procedure to find out

#10 Markus

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Posted 24 May 2004 - 12:09 PM

Josh,

I was pinching off the return line as outlined in the Haynes manual.

What would the color of the spark from the coil pack look like? Should it be Blue or Orange?




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