North American Turbocoupe Organization



Fuel pressure
turbotbirdguy79 Offline
Senior Member
#1
I was wondering when you turn your key on and your fuel pump kicks on,is the pressure supposed to go up and then drop instantly?Mine has always done this.When you turn the key on and hear the pump kick on,the fuel pressure will shoot up to 40psi and then instantly drop back down after the pump kicks off to 0 psi.I searched and read that it is supposed to hold pressure.Maybe my gauge is wrong?Is ther any thing else that would cause this besides the pump or leaking injectors?Im positive I have no leaks in my lines either.TIA.
1988 Tc,SC50(.63),Bosch BPV,Coolingmist methanol injection activated at 10 psi,FMS big valve 1.89/1.59 head,a234,ported E6,ported lower and upper intake,Gillis,3"downpipe,3"exaust,Kirbin AFPR,255 HP LPH pump,Racer Walsh adj cam pully 2* advanced*,K&N cone,MSD Blaster,autolite 103 plugs,T5 swap,3.73s,shifter,Centerforce stage 2 clutch,motorcraft tuneup.
Reply

Pete D Offline
Administrator
#2
Could also be a bad FPR. Run the complete diagnostics to pinpoint what the problem is.
http://www.turbotbird.com/techinfo/Fuel_...ostics.htm

The manual says it should loose no more than 2 lb in 3 min. Some aftermarket regulators bleed out faster than that, but no way should it go straight to zero.
Pete Dunham


Reply

turbotbirdguy79 Offline
Senior Member
#3
Im going to run the FPD tommorow.I was listing to the injectors while jumping the fuel pump and when the pump is running,you can hear a gurgling sound by the FPR.I took off the line and dont smell gas,but that does not mean its still good.If a injector was hanging open,I would think that it would not run very well,or blow black smoke on start up but it does not.My fuel pressure under boost will not go higher than 50 psi either.It gets there and the gauge needle bounces around and this is at 19 # of boost.I think this is gonna be a fun one to figure out.Thanks
1988 Tc,SC50(.63),Bosch BPV,Coolingmist methanol injection activated at 10 psi,FMS big valve 1.89/1.59 head,a234,ported E6,ported lower and upper intake,Gillis,3"downpipe,3"exaust,Kirbin AFPR,255 HP LPH pump,Racer Walsh adj cam pully 2* advanced*,K&N cone,MSD Blaster,autolite 103 plugs,T5 swap,3.73s,shifter,Centerforce stage 2 clutch,motorcraft tuneup.
Reply

Pete D Offline
Administrator
#4
Quote:you can hear a gurgling sound by the FPR.
The fuel pump can, in theory, pump as high as 120 psi. Once it reaches the regulator's base presssure, the regulator is going to allow the excess to return to the tank.

The diagnostics will sort it out.
Pete Dunham


Reply

Jeff K Offline
Administrator
#5
The FPRs do make a muted gurgling sound when you run the pump.

Assuming the FP gauge is relaying valid info, I dont think the problem is leaking injectors. If pressure dropped as fast as you describe, the car would start hard, and puff out a bunch of black smoke on startup.

That leaves FPR or the anti backflow valve in the pump itself. FPR can leak internally with no gas in the vac hose. I personally have seen more pumps with bad antibackflow valves causing your problen than bad FPRs causing fast bleed down of pressure.
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
Reply

turbo d Offline
Member
#6
I ran into a similar problem with mine, and it turned out that the little 90 degree rubber hose coming off of the fuel pump had a slice in it. It was barely visible as it was more like a little pin hole. I guess my pump was pressuring the system and then letting the pressure and fuel back into the tank. Hopefully its just a bad fpr, because I can't think of anyone who enjoys dropping a fuel tank.
good luck
Darrell
Reply





Users browsing this thread:
1 Guest(s)



Theme © iAndrew 2018 - Software MyBB