my 86 305 tpi was running fine and still does

but:

i installed this digital fuel pressure gauge, worked fine for liek 2 weeks then it had lo pressure errors. i figured was just the sensor or bad ground

car starts and drives fine so didnt think much of it

the company send me a new sender for free anyway i installed it and played with the gauge it self and i finally got some readings thats when i noticed while watching my pressure drop when i prime the pump with the key turned

goes to 30-40 something then once fuel stops priming its drops 25-24-23-22 etc... and goes to 0 within 20-30 secs

i put a manual gauge with a needle on my schrader valve same thing wont hold pressure unless the car is running both gauges read mid 40's with vacuum off the regulator and mid 30's with the vacuum connected

but as soon as the car is off it drops to 0 within 30secs give or take

while engine running at idle its around 33psi and holds. 43-46psi with the vacuum line disconnected and holds

car has been parked for a while like over a year only drivin a few times to get gas or emmisions etc... until i finished restoring the body and interior

i havent pinched the return line to see if its the injectors or regulator yet!

injectors are a yr old brand new ford 19lb injectors, diaphram is a yr old brand new with an adjustable crane regulator top


no fuel out of the vacuum line of the reglulator


so honstly because i jsut want to drive and enjoy the car im tired of the whole sharade after doing botl on engine upgrades doing teh whole body and painting and custom interior. i jsut want to drive the dam* thing spet almost 2 yrs since i bought fixing it up and havent even had any fun with it yet andthis problem just started after a week of finally breaking her back into shape on the road.

but like i said car drives fine starts fine starts even better when warmed up

if the car passes the pinch return line check up

if its a leaking injector ill be pissed since tehy are new but since the car drives and starts fine i should be ok right? to just keep driving it?

theres already injector cleaner in the fuel tank last time i filled up

plus i dont have a skip or miss so could that clear any injector problem?

im guessing my fuel pump?

anyone else want to give their 2 cents?

 

I don't think that's a big issue unless the injectors are leaking the pressure out (doesn't sound like the problem) or it's dribbling out on the ground somewhere. FP regulator can be a bit leaky and pass the pressure back to the tank, or it can back-feed through the pump into the tank. Not supposed to happen, but they sometimes do. Haven't heard of anyone having any major issues becuase of either of these problems. If it's right while running then you're doing fine and I wouldn't hesitate to go have fun driving it.

 

ok thanks, yea car drives fine and regulator seems fine like i said doesnt leak into the vacuum hose and the vacuum lines is working since the pressure changes with it connected and disconnected

and no i dont see fuel on the ground

my biggest concern is if this is signs of the pump or pulsator going but i dont think the car would run as good as it is if it was the problem.

most likely a stuck injector which would suck since they are new but like i said no miss or skip at idle or when i rev it

id rather its the pump other than the injectors because ill pay a shop to do the pump but not teh injectors cuz i do the injectors but just dont want to becuase its like a 9hr process for me and the 9th injector setup is a pain with how i gota bolt the runners and fuel rail and everytihn else in a certain order and how the runners have bolts on the inside under the fuel rail to get to which is a pain so if its the pump id be happy haha

but anyone else see a problem with driving it as is?

 

it's not a problem to keep driving like that, but it's the fuel pump that is the issue. There is a valve in the pump that is supposed to hold residual pressure when the pump is off.
I assume you are having hard starts as well

 

actually not really, maybe 2-3 seconds to start up. my camaro 2.8 is instant it amazes me but yea the v8 trans am takes a few seconds, idle shoots up then settles down right away to normal maybe cuz its burning off the excess fuel or just takes a second to build up fuel pressure

 

I am not sure if it is the pump or not. I have the exact same problem and I have already changed my fuel pump and the relay. When I pinch off the return line I am able to hold fuel pressure and it will stay for a good 30mins to and hour unless I start the car and shut it back off. I think it may be my regulator but I figure I will just drive it until I swap out to the stealth ram. It is hard to start every great once in a while but once oil pressure comes up it fires right up.
Semper FI
Willie

 

yea unless there is someone who says no no somethings way wrong im just going to drive it and enjoy it. i drove it all day today, starts right up and just not going to think much of it.

i dont know how the regulator could be at fault if its not leaking out the vacuum hose

anyone have any thoughts on this?

 

Bobby, I had the exact same issue. Turns out my fuel pump went bad. Would prime fine, go to 45PSI, then slowly bleed off to almost 10PSI in a matter of seconds when the pump stopped priming. Factor was the check valve in the pump whent. It happens. You going to Thompson CT Speedway this Sunday? My club is going for 9AM, there's about 10 of us so far.

BTW, sure you can drive your car as is until the day comes when the pump takes a complete dirt nap because your pump won't even prime the system with enough pressure to start, then you have to get towed home..this happened to me back in April.

 

hey not sure whats going on sunday ill definately keep it in mind.

weird thing happened today. my car is back to normal. it held pressure at like 35-40psi after priming

weird but ill take it, yesterday was still dropping to 10 or less ya got me haha