Fuel 1992 351w Swap Fuel Pressure Issue/problems - Please Help!

stussy2870

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Apr 5, 2019
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Hey Guys,

I'm relatively new here and to the Fox-body scene.. I had the chance to scoop up a really nice 92 that had been 351w Swapped (Still has EFI). Since acquiring the car I'm noticing a few things that aren't right. The first and right now - most important - the Fuel Pressure and subsequent issues b/c of it. Let me explain..

The car has a no-name ADJ FPR on it with a built in gauge. The gauge reads 90-95PSI !!!. There is also a HEAVY gas odor in the Oil. I suspect the absurd pressure is washing fuel down the cylinder walls and thus creating the gassy oil. Here are some of the things I've "tried"..

- Checked vacuum - There appears to be vacuum at the FPR as when the line is removed the FPR's gauge moves (increases pressure) about 4lbs.
- Manually sucked on the vacuum hose to pull up the diaphragm in the FPR - the gauge again moves - albeit ever so slightly - 4lbs ish..It appers to still be air-tight
-Turned "out" the screw to lower the pressure - best i could get it to was about 75lbs before the screw fell out- At that point the car would barely idle.
-Tried a base idle reset (youtube video) at 75lbs and wasnt able to stabilize the idle at all..
-Reverted back to 90+/-lbs and was able to get the idle back under control but at the cost of increasing the Fuel Pressure again..

What i plan to do next:
-Test the Shrader valve with another Gauge (tomorrow)- Im expecting no changes here given the gassy Oil issue..
-Disconnect the Return line and see if the pressure releases (indicating a potential clog back to the tank)..Kind of hoping this isnt the issue..
-Replace the ADJ FPR w/ a stock one.. Easiest and cheapest fix..

What do you guys think? Am i missing anything, anyone have a similar experience?

Lastly -- Im in Pittsburgh- just north of it but that doesn't matter.. what i am looking for is anyone (Shops, people, cats, dogs...etc) who are well versed in these cars and their nuances :) .. That i could potentially go to in these types of scenarios.. Any leads whatsoever based on my location would be EXTREMELY helpful.

Thanks!
Paul
 
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jrichker

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So far, your plan is right on track. Either the return line is blocked or crimped or you have a bad FPR.

To trick the fuel pump into running, turn the ignition switch to the Run position. Then find the ECC test connector and jump the connector in the Upper RH corner to ground. The fuel pump should run unless the wiring has been tampered with or the fuel pump relay is bad

 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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Here are some things to do before you go much farther:
change the oil and filter, continuing to crank and/or run this engine with fuel contamination will kill that engine. Look for things like the color of the injectors, this should tell you what size they are, the second fuel pressure gauge is also a good idea.
let us know what you find.
 

stussy2870

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Apr 5, 2019
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got some more information tonight..
- Checked the Gauge when i got home.. it was at 62lbs..Pushed in the shrader valve and ...nothing.. no pressure/gas at all..
-Primed the system, jumped to 92 on the gauge, checked the valve again, this time there was gas/pressure..
-ran the motor for 2-3 minutes, shut if off completely and then re-primed the lines (turned the key to ON w/o starting)
-Checked 3 hours later.. Pressure dropped to about 70lb's

From this information, i think its safe to say that i have a leaky injector or injectors.. Do you guys agree?

next steps- pull the rails up, take all the injectors out of the manifold, reattach to rail and re-pressurize. Once pressurized ill wain to see which are leaking unless you guys know of a better way??

Thanks!
Paul
 

Steel1

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Aug 18, 2017
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Fuel pressure will drop over a period of a few hours, I wouldn't condemn the injectors just yet.
I would continue to do fuel system check to verify cause, just fyi I run a stock regulator on my 393w.
 

stussy2870

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Apr 5, 2019
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Fuel pressure will drop over a period of a few hours, I wouldn't condemn the injectors just yet.
I would continue to do fuel system check to verify cause, just fyi I run a stock regulator on my 393w.
Thanks Steel1 - Since i clearly have a Gauge issue (Reading 60lbs w/ no pressure in the line) - ill obviously retest with a secondary gauge to verify proper pressure etc. Assuming pressure is good, how many other ways could gas get into the Oil besides a leaking/failing injector? I will replace the Adj FPR w/ a stock one for good measure next.


Get a repair manual,
Great idea - and i will for sure. However i don't have one right now and i have a right now kind of problem.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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My major concern right now is have you changed your oil?
cranking or running the engine even for a few seconds can kill the cylinder walls.
 

stussy2870

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Apr 5, 2019
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Thanks General- i appreciate the urgency you're providing. It helps to know the severity of these issues which i'm learning here -REAL quick!

Anyway, Oil was changed about 1 weeks ago. (by the previous owner) - there is maybe 2 hours of total run time on the car while in my possession. He claimed he changed the plugs/oil/filter 2 days before i bought the car. Visual inspection of the Oil and Filter would lend me to believe that to be true.

I've had it since Thursday. It has about 2 hours of total running time on this batch of oil (obviously an estimate). When it was test driven, and even driven after the sale it didint smoke at all.

I have new oil and filter in the back seat of my daily - will be replacing it over the weekend.
 
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Boostedpimp

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*edited* Change that oil asap! sorry didn't see your post from a few minutes prior to this but glad oil was changed

Also I would replace the afr/gauge with factory one and a new known good gauge on the shrader valve. If you still have those high pressures then I would look over the fuel lines for pinches or restrictions
 
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stussy2870

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Apr 5, 2019
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Change that oil asap!

Also I would replace the afr/gauge with factory one and a new known good gauge on the shrader valve. If you still have those high pressures then I would look over the fuel lines for pinches or restrictions
Yup, got all new oil/filter for this weekend. i am NOT driving the car at all. Also got a Sharder Valve Fuel Pressure gauge on the way. My plan is to replace the Adj FPR - revert it to a stock one and retest the pressure. I have a feeling that a bad gauge has led me down the wrong path. I'm not sure how else gas gets into the Oil on these EFI cars other than the Injectors so thats my next logical progression - that is, once i confirm Fuel Pressure is correct of course.
 

stussy2870

Active Member
Apr 5, 2019
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General, there are a few different Shop/Service manuals available. Do have a recommendation? The FOMOCO one is pretty pricey- is that worth the extra $$ over say a Chiltons?
 
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