narrowed it down 2 the fuel system...

93thunderbird

Registered User
ok here is my problem http://www.sccoa.com/forums/showthread.php?t=71305&goto=newpost ok well my fuel press. gauge dosnt leave 40 psi (as soon as it does thats when the car breaks up n wants 2 stall) i unplugged the vac line to the pressure reg. and it dosnt pass the 40 psi it just pins the 40, even reving it up it wont pass 40psi... ok i drive the car and ill park it 20-30 mins later i check the gauge from 40 it drops down to 10psi.. now i just put a new press. reg. about 5 months ago do you think its the reg. leak in the system,fuel pump,injectors what do u guys think
 
If you pulled the vacuum line on the regulator and the pressure never changed I would be looking to a leak on that line. AllData says this:

Key On Engine Off 35 - 40 psi
Key On Engine Running 30 - 40 psi
Engine Running Vacuum Hose Disconnected From Fuel Pressure Regulator 35 - 40 psi

42293017


Ground this terminal to run the fuel pump(KOEO) . After you shut the pump down monitor the pressure. you shouldn't lose more than 2lbs in 3 minutes. My guess would be the check valve in the fuel filter or a dirty injector that's leaking. Take it in and have an isolated fuel system cleaning with a real injection system(nothing you pour in your tank is actually going to do you any real good).

Good luck man
 
With the vacuum line removed it's supposed to stay at 40 psi...if it was doing the same thing with vacuum line connected then the regulator was bad or the vacuum line was bad.

David
 
at idle....

if im not on the gas, the gauge reads 30psi (around 26-28) when i apply the gas it will go up to 40 psi (but will never break 40psi (36,38), if it does the car bucks/stalls if i keep holding it) im sorry i thought once you took the vac line off it goes to 50 psi.. so its normal with the vac line off but why cant i hit anything more then 40 psi?
 
The pump doesn't make enough pressure, and the regulator is designed to only build 40psi. This is sounding less like a fuel issue. At what RPM is it doing this?
 
Okay just read your original post(should have done that first)....

If you just replaced the dist shaft and cam sensor, is there a chance it was off or has slipped? Since they control your injection timing, being off just a little would allow it to run fine at a lower RPM and only be reflected when the timing advances and the air flow reaches a certain threshold. It's at least worth looking into.....
 
hey rbh...

im sorry i didnt change the dis shaft? i changed the "dis mod" or aka ignition mod and the cam sensor (reason y i changed them was b/c of the bucking) but i looked closer at the fuel press. guage thats why i think its a fuel problem.. you guys said the reg. and pump cant handle more then 40psi? my car used 2 hit 50psi WOT or when i get 5-12psi of boost i also smell gas time 2 time (sharp turns? lol i have really pin pointed what causes that)
 
Bucking when you attempt to go into boost, is most often caused by plug wires or the spark plugs. When was the last time they were replaced ?

David
 
its not the wire/boots

if u read my link at the top it will explane all of that... its a fuel issue, im ganan try the fuel reg (ganna go with ford this time) ill keep you posted
 
From what you have written, The fuel pressure is fine and doing what it is supposed to in response to throttle pos. and engine load. The only concern there might be the pressure drop(see above for press. drop specs.). That would not cause your concern though.

I have over looked something that very well could be the issue. Have you checked your vacuum/pressure switch? It may not be switching and causing this exact problem. I'll look on alldata and pull the diagnostic procedure for it for you.
 
93thunderbird said:
if u read my link at the top it will explane all of that... its a fuel issue, im ganan try the fuel reg (ganna go with ford this time) ill keep you posted

I read your other post and I still think it's your plug wires. Buy a good set of wires and some new plugs and I'll bet the bucking goes away. BTW, bucking is generally caused by ignition..low fuel pressure will cause bogging until the upper rpms, then will it will begin to miss.

Best bang for the buck on plugs wires is a set of Taylor wires from Summit. Do a search on "Taylor" for the part number.

David
 
RBH Racing said:

UMMMM, are you expecting us to see an image here. If so, it needs to be uploaded. You are attempting to post an image that "lives" on your hard drive and therefor we can't see it. (can you?)

Tracy
 
wasnt the pressure reg.

it still wont pass 40psi without bucking runs like a champ though (i can drive up 2 any speed) just cant pass like 3 psi of boost (witch will pass 40 psi of fuel pressure) fuel pump??? what do u think or a leak in the line?
 
93thunderbird said:
it still wont pass 40psi without bucking runs like a champ though (i can drive up 2 any speed) just cant pass like 3 psi of boost (witch will pass 40 psi of fuel pressure) fuel pump??? what do u think or a leak in the line?

Being down 3 psi on fuel pressure isn't going to make it buck. BTW, The regulator can be set anywhere between 38 and 41 psi and still be within factory specs.

IMO, Your not getting any additional fuel pressure because the motor starts bucking when you try to apply boost. Still think you have an ignition problem and it's most likely the wires.

David

PS: If you want to test the pump, supply compressed air to the fuel pressure regulator and see if the pressure increases. Be sure to turn the pressure regulator on your compressor down to about 10-15 psi or you risk rupturing the fuel pressure regulator diaphram.
 
changed the spark plugs/wires...

i changed my spark plugs n wires (went with a colder spark) ill tell u what.. i def feel more power through the rpm range but the bucking is still there... (fuel gauge still reading 35,36is idle) weak pump or what?
 
Back
Top