[viperlocc]

so its a new holley 110gph mech. fuel pump. stock lines from the take to the pump, and bigger from the pump to the carb. clear filter right outside the tank which is full and clean (new filter inside). clear filter between the pump and carb which is full when i first start the car or let it sit for a while. empties out after it warms up and sputters fuel into it.

after its warmed up, i get between 3 and 5psi of pressure. when its first started cold its about 6.5 to 7psi. if i get on it a little bit, the pressure begins to fall to 3ish. The filter between the pump/carb is sputtering with fuel (not full, not even half).

all new lines (cept the stock in between the pump/tank).

am i getting low pressure because it may be to small of lines? i wouldnt think so seeing as its only a 110gph. i checked all the clamps and replaced most of the rubber lines to new fuel lines.

[86er]

where is the pump mounted, middle of the tank or lower? Secondly, where is it drawing power from? If it has a hot wire running from the front of the car all the way to the back with no relay thats prob the problem.

Power loss over the resistance and length of the wire. If power is coming from the front of the car you have to run a relay to keep the volts at the pump up.

try wiring in a relay and see if that fixes it, im about 99% sure of it

[viperlocc]

mechanical pump which is bolted to the side of the engine

[86er]

bad diaphram

[viperlocc]

bad diaphram...inside the pump?

[86er]

the rod and the diaphram are all that are used to create fuel pressure, if the rod moves, the only other piece of the puzzle is the diaphram

[viperlocc]

but why would it give me full pressure when cold than warm?

only have about 50 miles on it, think jegs will take it back and give me a new one?

[88-gt-t-top]

prob. not, unless it's under manufacturer waranty. even then... kind of iffy on used parts

[viperlocc]

well ill throw the stock one in and see what happens.

i just dont believe in the "even new stuff can be bad".

any way i can open it and see if its bad?

[Iownastang]

why dont you believe new stuff cant be bad? Things happen all the time..

[viperlocc]

well i shouldnt say i dont believe in it, it just really hasnt happened to me in a very very long time.

[86er]

should be a bunch of screws around the middle of it, take them out and it will split open.

hot and cold expansion, the rubber is prob pulled tight when its cold when it warms up the tiny hole or rip expands and becomes bigger

Careful when you pull it open, spring will want to go flying

[M L Struck]

If the diaphram is bad you should be losing fuel somewhere and if it isn't on the ground it's in the motor, pull the dip stick and see if it smells like gas.