North American Turbocoupe Organization



Holding fuel pressure after motor is turned off...
Ryan H Offline
Posting Freak
#1
My fuel pressure gauge used to show that I would hold around 32 PSI or so after the motor was turned off for about 5 minutes or so. Then it'd drop down to like 10 PSI eventually and maybe like 30 minutes later it would read 0 PSI.

Now when I shut the car off, the reading almost instantly drops to 10 or below. If the car has been parked for a while, I can smell fuel near the exhaust. I have inspected all of the fuel lines on the passenger side of the engine and the fuel rail and lines leading to it. Could the fuel pressure drop be a leaking injector and the fuel vapor getting out through an exhaust leak? I'm pretty sure I have a small one on that side of the motor, just haven't had the time to retorque the bolts to everything.

To inspect the lines, I flipped the key to RUN and back off a couple times until my gauge read like 40 PSI, then flipped it a couple more times to make sure there was plenty of fuel pressure in the lines to make it leak. I sniffed, felt, looked, tugged, etc on every fuel line and didn't come up with anything. There is no fuel in the engine bay or near my fuel rail. Does it sound like I'm on the right track with injectors?

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Ryan Harris

88 TC, 5 spd, B&M Ripper Shifter, Walbro 190 LPH, Aeromotive FPR, K&N, 3.73 rear, KS disconnected, BCS bypassed, 89K miles
'88 TC Smile Walbro 255HP, Stinger FMIC, PIT BOV, Pro 5.0, Kirban, RR cam, FRPP strut tower brace, T3
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jmthunderbirdturbo Offline
Posting Freak
#2
seems to me your leak is on top of the tank. maybe the clamp on the fuel pump is worn or broken. also check you fpr. those aeromotives tend to leak, change pressure, stop flow all together, etc etc. the bad reg could cause it to run rich, and give you a fuel smell...definitly check for fuel coming off the top if the tank...and check for good base fuel pressure too. from what i hear of those aeromotives, they have issues. ive heard that sometimes its a guage read error, but i have seen a few on turboford.org that have simply stopped flow(block the return altogether), and killed pumps.

moller
AM

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1987 5.0 sport coupe, intake, exaust.>for sale<
1987 tc, goldie, mods: mandrel bent downpipe to cat with turn down, gillis valve, 155 lph pump, kirban afpr, 100 psi fuel guage, handmade pvc cold air intake, optima. 15.457 @89.22(#24)(special thanks to turbocoupeturbo)(firedoctor)
1988 mazda truck, 431000 mi.
Buisness partner in Aerobird Motorsports.

[This message has been edited by jmthunderbirdturbo (edited 08-26-2005).]
APRIL 2018 - LOOKING FOR A NEW CAR. PM me if you have an 87-88 roller or cheap TF for sale.
1988 TC 5MT-Blue/Blue check-off car. resto-project.
2006 Honda Odyssey 5AT, baby-mobile.
2013 F-150, 5.0, 6AT, 4x4, snow white paint.
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turbocoupes Offline
Senior Member
#3
When you ck fuel pressure with 1 key on,starting with 0 psi,what is the pressure reading and what does it do when the pump stops? If the pressure drops quickly below spec I would suspect Fuel Pressure Regulator with driveability concerns like poor fuel mileage and occasional "runs rich" also a slighty longer than normal crank to start time and the fuel smell could be vapors getting into the intake system seing as the vacuum line attaches to the upper intake. Fuel smell by the exhaust...is it front or rear of the vehicle??? I have had charcoal canisters (passenger frt on frame rail) vent to atmosphere and smell pretty strong as if there was a leak. Need more info on this one. Also on dropping fuel pressure I have had a splitting fuel line at the fuel pump do some crazy things also...

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Garry McVey "BIRDS OF A FEATHER" Birdoprey always in flight... TBird TC owners are usually wingin' it
TC's 83 project, 86 donor for 83, 86 FUN street car,87 RIP, 87 blue to be stock street car, 87 red donor for blue and others, 87 red daily driver, 88 street and strip HALF WICKED right now, 87 XR4ti project,80 pinto wgn project
Garry McVey "BIRDS OF A FEATHER" TBird TC owners are usually wingin' it
TC's 83 project, 86 donor for 83, 86 FUN street car daily driver with speed equipment from Red 88 donor, 87 blue to be stock street car, 87 red donor for blue and others, 87 red donor, 88 street and strip(now a donor) 14.01 chasin 13.0's, 87 XR4ti project,
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Matt S Offline
Posting Freak
#4
I had a pressure drop that seemed way too quick a while back. So they went for a cleaning and flow match. One of my injectors was leaking slightly from the deposits on the pintle; he called me and asked if I had noticed pressure drop or weird things. (duh..it's a TC!)
I sent him the originals with 4 extra I got off ebay and so he picked the best 4 of 8. My pressure didn't drop nearly as much after.
A good clean/flowmatched set, imho, should be some of the first things you do after all that other intake/exhaust/sensor stuff. It has been 17 years or more on some pretty shady gas, sitting for months a time or two. [Image: biggrin.gif]
If you have... [Image: redface.gif] But the fuel smell tipped me off. The regulator just lets it bleed back to the tank too quick.
Sold it Sad*
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tps87turbo Offline
Posting Freak
#5
You may also have a leak from the little rubber hose inside the tank that connects the fuel pump to the mount. I also may be the pump itself. Just some more food for thought.

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Tony Sceia -

HIS Red 88 TC http://www.turbotbird.com/showroom/TySa_88tc.html



HERS - Blue 87 TC, fully loaded with every option, Gilies Valve, K & N Filter, 3-core Radiator, New Paint...just needs to be put back together, Interior re-done & get some exterior parts.

87 TC - Bought as a Parts Car, & will remain a parts car now that I found the blue one.
Tony Sceia -

HIS Red 88 TC
http://turbotbird.com/showroom/data_r-z/...a_88tc.php
HERS - Blue 87 TC, fully loaded with every option, Work in Progress
87 Gray TC Parts Car - Gave to BJL and is now his daily driver
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Pete D Offline
Administrator
#6
Non pumping pressure is maintained by 3 things. 1. A check valve in the pump which prevents backflow from the feed line to the rail. 2.The FPR. 3.injectors (non-leaking) A leak in the feed line at the pump would affect rate of leakdown. A leak in the return line would not, I don't think, unless the FPR is also bad. The factory spec for leakdown is not more than 2 psi in 3 minutes. I've noticed that my Kirban bleeds down a little faster than that, but we aren't talking going from 40 to 0 in 2 minutes. If you run the complete fuel system diagnostics there are tests to distinguish where the leakdown is coming from.
Pete Dunham


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Ryan H Offline
Posting Freak
#7
I found an old Mustang forums post saying I can figure out where the leak is by cutting up an old fuel filter (I happen to have one! yay! [Image: biggrin.gif]) and placing rubber fuel line in place of the filter, then clamp the line after it is pressurized. If the pressure drops from the supply side then its in the tank, if it drops from the other side then its in the injectors/FPR. I am gonna try this when the clutch is back in.. TC's just LooOoOOove giving me problems! [Image: biggrin.gif]
'88 TC Smile Walbro 255HP, Stinger FMIC, PIT BOV, Pro 5.0, Kirban, RR cam, FRPP strut tower brace, T3
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Pete D Offline
Administrator
#8
How you going to measure pressure on the tank side? And why do you cut up a fuel filter, you don't mention using it?
And yes, I just got up and haven't had coffee yet [Image: biggrin.gif]

[This message has been edited by Pete D (edited 08-27-2005).]
Pete Dunham


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Jeff K Offline
Administrator
#9
You cut up the filter for the tube ends that go into the fuel line fittings. Without those tube ends from an old filter therre is no way to connect to the fuel line fittings.

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 23 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 04 Taurus Duratec (wifes car) // 91 Topaz (daughters first car)
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Pete D Offline
Administrator
#10
Thanks Jeff. Things are clearer now after a couple cups of coffee [Image: biggrin.gif]
Pete Dunham


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