FPR Question?

Folks,

For the last while I've been fighting with an overly rich condition at idle and part throttle, but a lean condition under heavy load conditions. When I downloaded the KAM fuel trim tables from the EEC, it had the fuel trims maxed to try to lean things out because it was so rich on the lower sections.

I have being adjusting my lower MAF curve to bring everything back in line and its working, but I'm seeing large adjustments now. I actually adjusted my upper curve to make the car richer because its pinging now over 8psi boost, so I'm just playing that safe until I get a wideband.

Dave D suggested I may have another problem and I am agreeing, as I shouldn't need to adjust the curve down that much. I checked my fuel pressure and this is what I get:

-Key on, engine off I get 39psi and holding.
-Engine idle I get 32psi
-rev the engine hard and I easily get over 50psi.

Now my question is, is it possible for the FPR to have a small fuel leak through the diaphragm so fuel gets sucked in while in vacuum, and even possible to actually blow air into the fuel rail when in boost, but still operate enough to give me proper fuel pressure?

fturner said:

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Now my question is, is it possible for the FPR to have a small fuel leak through the diaphragm so fuel gets sucked in while in vacuum, and even possible to actually blow air into the fuel rail when in boost, but still operate enough to give me proper fuel pressure?

Click to expand...

Yes. If you can get at the vacuum line on the FPR you can check for fuel in it. There should be ZERO, NONE, ZIP fuel in that vacuum line.

Ok, now if I do need to replace it, do I just go ahead and get an adjustable then set it to 39psi for now, or just get a stock replacement...

Guess I should just price what a stock one costs I guess.

I think "Kirban" will be a good choice. Or that's what I've been told...

Fraser,
I have had the same problem befor with stock injectors and a 76 C&L maf. I was rich from 2000-4000 rpm. Since changing to 42LB injectors I now only have a rich problem when I stab the gas I did find rasing the palse witdth a small amount helped to stop the black smoke as well kept the AF even this was on my sct chip and using my LM1 to be safe.

-Key on, engine off I get 39psi and holding.
-Engine idle I get 32psi
-rev the engine hard and I easily get over 50psi.

that sounds about right for them it's hard to tell with out driving the car. To get the readings

Well, so far the price for a stock replacement FPR and the Kirban adjustable are about the same .

I'm starting to lean toward the Kirban even though at my power levels at this time I doubt I'd be over running the 42# injectors for awhile.

Decisions decisions decisions..... and I still need a WBO2

Thanks for the reply Jason, my problem is the whole lower half of the MAF curve has to be substantially dropped to bring everything back in line. The fuel trims where maxed out. The upper half I need to increase the amount of air in the curve because the car is pinging up there. The adjustments aren't small either, and with only having what I have now I'm still sitting around .85 avg on the fuel trims.

If you do go for an adjustable, I found a way to relocate it so it's accessible.

You need some Aeroquip FC332-4 AQP hose to replace the factory plastic connector tubing and extend the fuel rail. 8-1/2 to 9 inches each for the back pair and 12 inches for the drivers side. The FPR housing can be moved from the inner mount location to the outer threaded hole on the back of the driver's side head. This also moves it down a bit. A 3-1/2 inch, 10mm (1.5 pitch) bolt and a 1-3/4 inch, 1/2" copper pipe as a spacer wiil work. I threaded up a stud from 3/8 aluminum round stock. This puts the FPR just behind the valve cover. The entire fuel rail should be removed for this job and be careful not to scratch the barbs.

Interesting thought... I wonder if would work with having that monstrosity of a ABS brake system that the older cars have sitting there. Could you take a couple of pics of where it sits?

I have a '94, so I guess it fits.

I was waiting till I get the cowl back on to take a pic and that's the last thing I want to do, just in case. Getting held up waiting on front poly sway bar bushings. *&^holes waited 18 days from payment before shipping because it's "international".

Excuse the rant but I feel much better now.

LOL! I know how you feel. Several times now I've ordered parts etc, paid for them only to get told that they refuse to ship the part internationally and refunded my money. I lost out on a new pax side cowl piece so my car still sits with a new one on the drivers side and an old cracked up one on the pax side .