hello
i have a fuel pressure problem... i want 45 psi.. i have 41 psi of fuel...
at first when i tried to up my fuel pressure it would not increase so i figured my AFPR was broken so i went out and bought the accel AFPR with the diaphram whitch dinged me 180 bucks at the local parts place. i put that on and same deal at idle with the vacum hose diconnected my gauge says about 41 psi.. so ive changed between 3 gauges all say the same thing....i canno get the fuel pressure to increase with myy new regulator.... i have a brand new walbro 255 fuel pump witch i had 45psi and it was fine.... i checked all of the lines and there are no kinks or dings in them. the fuel filter is brand new.. i mean like 450 km on car since fuel filter...

I CANNOT INCREASE FUEL PRESSURE PAST 41 PSI.... I CANT FIGURE IT OUT.

Speed

 

another interesting fact... there is no change in psi on the gauge whether the vacume line is hooked up or not... shouldnt it be radically different?

 

14.5 volts to fuel pump at idle

 

the problem must at least be partially with the no change in pressure with the vacume on or off.. i cant explain it..... would it do that if i had a vacum leak?
i think im going to check the vacume of the intake.. any ideas on what TPi vacume should be?

 

Take it easy man theres a fix there somewhere. I dont have much more input to give than that so I hope support is enough at this time and others will chime in as to why the heck the pressure wont go where you want it to

 

Vacuum should be around 19-21 in/Hg at idle, stock cam. If you have a performance cam, it will drop. I have the LT4 hot cam in my 350 and it has 15 in/Hg at idle. Normal for that cam. I will be digging in to the shop manual later today, I will see if they have any info for fuel pressure not changing with vacuum.

 

I'm wondering about vacuum leak now... If the vacuum is not present then it wouldnt make any difference in the fuel pressure AND it would make it run like a back house at idle....

 

OK info from the 1988 shop manual. First thing to check with this problem is to ensure you have vacuum. The test is to check that with the engine idling, that the pressure drops 3-6 psi when you attach the vacuum hose. If it doesnt drop, they then tell you to apply vacuum to the regulator ( hand pump ) and see if the pressure drops. If it doesnt drop then the regulator is at fault. If it does drop, then you dont have any vacuum to the regulator. Regarding the low overall pressure, ( factory regulator and everything working correctly, range is 40.5 - 47 psi), they indicate that the problem could be the regulator, the fuel pump or the pulsator (both in the tank), a leaking coupler , again in the tank, leaking injectors or a blocked fuel line. Filter blocked, or a clogged line. Did you make sure that you installed the filter correctly? They are directional. Are you sure that you asembled the regulator correctly? Did you replace the in tank filter when you replaced the pump?

 

brand new walbro fuel pump and pickup sock pulsator delete
brand new fuel filter installed correctly
brand new accel AFPr installed correctly

this same setup was running at 45 psi but i did a motor swap for my new motor and suddenly i couldnt get my pressure up... so i replaced the AfPR from BBK to Accel with a new diaphram and still no adjustablility or change in pressure

will check for vacume next.

 

Try clamping off the return line at the rubber hose. You can use a pair of vice grips. If the pressure comes up, then you have an issue with the regulator. If the pressure still wont rise, the you have an issue with the feed circuit. Do the test with the engine off. Another thing to try is this, return hose clamped off. Just turn on the key and see what the pressure reads. Then adjust the regulator and turn the key on again. If the pressure goes up and holds then the regulator is probably new defective.

 

Good tip I have special line crimp pliers for just such a purpose if you need. They look like Doctors forceps except they are 4" long and smoothly contoured so as not to damage the line when you pinch it but they have the same ratcheting grip effect as dr's forceps ya ya

 

no vacume leaks.. 17 hg of vacume
next i will try the other stuff

 

So, vauum line n or off makes no change in the fuel pressure reading? I/e none at all?

Does the vaccum line to the AFPR smell like fuel?

 

I am having the same problem witha a TPI parts AFPR.
It won't adjust under 46PSI and the diphram is new.
I called them and they tell me I prob have a clogged return line.