Fuel Pressure Regulator Fault Symptoms

davezed · Post by **davezed** » Mon Jul 10, 2006 5:17 am

Hi All
Would anyone out there in MS world know what are typical symptoms of a faulty FPR apart from a total failure to regulate? Is there a symptom for them to vary their regulation with under body temperature? I have a new 1995 Corvette rail mounted one on my set-up, are these reliable units?
Any help/feedback would be great

Cheers
DaveZZ

davezed · Post by **davezed** » Wed Jul 12, 2006 4:19 am

Anyone?

jsmcortina · Post by **jsmcortina** » Wed Jul 12, 2006 5:02 am

Fit a pressure gauge and you will have an idea what is happening.
Typically you will see 43psi with a primed pump but engine off. At idle the pressure will drop due to the vacuum in the inlet to say 38psi.

If you blip the throttle open the pressure should rise.

James

davezed · Post by **davezed** » Wed Jul 12, 2006 5:25 am

G'day James
I have a gauge fitted permanently, most of the time it sits on 41psi at idle (vacuum connected) and 47psi with vacuum disconnected (about normal I think maybe a few psi hi if the gauge is accurate). Sometimes however I see the gauge quivering by a couple psi. My motor has a bit of a cam (approx 50kpa MAP @ 900RPM), I've been having a nightmare in getting the car to run mainly below 2200RPM where it tends to surge or miss if I run it leaner than 13:1 AFR, I've had 3 different fuel pump combo's (all new pumps), changed filters many times so was wondering if this sort of behaviour could be FPR related. I also suffer from fuel hammer (audiable in car at idle) although its not too bad since changing to 4 squirts/cycle. I have tried MS extra and MS2, both react the same. Just curious if FPR are know to have "inconsistent" behaviour or do they just tend to "die" outright?

Cheers
DaveZZ

davezed · Post by **davezed** » Fri Jul 21, 2006 1:24 am

Ok, decided to view the FPR output, I placed a piece of clear tubing in the line and manually powered my pumps. What I saw resembled that of a spar bath, is that normal? Basically lots of air in the fuel as it came out of the regulator, this doesn't seem good to me, is there anyone out there how has viewed their FPR ouput? I had viewed a while ago the input to the fuel rails but that seemed ok, mind you it can be few hard to spot small bubbles if your not looking close enough...

Cheers
DaveZZ

jsmcortina · Post by **jsmcortina** » Fri Jul 21, 2006 2:01 am

Does the air go with time? At power on my fuel rails sound like they are full of air, but this goes after a handful of seconds.

If you continually have air then you will have serious fuelling problems.

James

davezed · Post by **davezed** » Fri Jul 21, 2006 5:56 am

The air is their (outlet of FPR) all the time (had it going for a few minutes) but appears much worse closer to the FPR outlet than it does a few feet down the line. This was from cold and by the sound it makes, also when it is hot. Can this be a FPR problem, I have had three different fuel pump combo's on this car (two new pumps and an old OEM pump) and the sound has remained constant. Thanks for confirming my fears, I think I got "flogged off" by my dyno man on this, reakoned it was normal but it just seemed a bit too unusual to me. This would account for my inability to tune my car after months of frustration!
Just to expand on my setup, I have an OEM style in tank swirl pot fitted with a lo pressure hi volume pump (new), this feeds my Walbro hi pressure external pump (new). The external pump then feeds my EFI fuel filter, from here I have run new 3/8 bundy tubing to my Edelbrock fuel rails, on the return rail (engine is a V8 ) I have a rail mounted FPR (new), this then goes to new 3/8 bundy tube right the way back to the swirl pot. I have tried the OEM pump on its own a while back and the sound I noted back then was just the same, although I didn't check it.
I thought I did my home fairly well on this side (obviously not), have I made any obvious mistakes or have I've just been unlucky?

Thanks

DaveZZ

jsmcortina · Post by **jsmcortina** » Fri Jul 21, 2006 6:06 am

Maybe it is simply air trapped in the line at that point? If there is no new air coming from the pump then maybe it doesn't matter?

The air in mine soon gets returned to the tank though.

Check for air on the inlet to the fuel rail - it does matter there.

James

davezed · Post by **davezed** » Mon Jul 24, 2006 2:28 am

Yeah, its a funny one, I got another piece of clear tubing and placed that on the inlet side of the rail. Again I ran the system for about 5 minutes but really couldn't see any bubbles (damm). When I turned it off as usual the pressure slowly dropped to 0 psi within about 5 minutes (although sometimes it holds pressure for hours), the strange thing I noticed after the pressure had dropped was there just before the inlet rail was a large air bubble forming. I guess it is possible that if there was air in the line and if it was small bubbles it would be very hard to see (although I did look as hard as I could).
Mmmmmm, what does this mean, am I barking at the wrong tree, do they all do this? My system doesn't appear to have a 1 way stop valve (I thought Walbro pumps had this internally), not sure if this could help but I guess I have to try something.... Anyone with any other thoughts....

Cheers for any/all the help

DaveZZ

superelbert · Post by **superelbert** » Fri Jul 28, 2006 1:14 pm

Looking at the pressure gauge on my car when idling a hot engine, I noticed that the needle was fluctuating quite a bit, and that the idle was not entirely even, allthough not bad in any way.

I am running a performance cam on my Dodge 318 V-8, but nothing really radical.

Could the fluctuations I see be caused by fluctuating intake pressure on the regulator vacuum connection?

To me this sounds likely, so I was thinking perhaps it might be worthwile to damp the vacuum signal to the regulator, perhaps by means of a restriction?

Anyone had similar experiences??

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Fuel Pressure Regulator Fault Symptoms

Fuel Pressure Regulator Fault Symptoms

interesting..