StangStang

Hello,

Been years since I have been on this site, turns out I had a profile.

I have a 351w pushing 400hp. Mechanical fuel pump system. The mechanical fuel pump is the only fuel pump on my ride.

I have a clear fuel filter up by the 600CFM Edelbrock Carb and the fuel pump is 110GPH pump.

My issue: After starting the engine, I have ~6psi of fuel pressure and the glass filter is full of fuel. After about 1 minute the filter has hardly any fuel in it and the psi drops down to 1 psi or less.

What I have done: I disconnected to fuel line just prior to the pump and put the line into a bucket of fuel. Fired up the engine and still have the same problem.

I don't think this is vapor lock because the engine isn't at operating temperature when the psi drops down. Am I right to assume that the fuel pump is bad?

Fuel Pump: Edelbrock Performer RPM Street Fuel Pumps 1725


Thanks in advance for the help!

StangStang

bop11

Sounds like you have a sticking pressure relief plunger and or a bad diaphragm. Either rebuild the pump or replace it.

69mach1377

Replace it. I had one of those and they last long. Went to a carter electric.

StangStang

Thanks for the replies. I called Summit and they were very confused that this would happen.. They sent me a new one for free. I will post my results.

69mach1377

Free is good...

67mustang302

Could be an obstruction in the feed line to the pump. How old is the tank/line? Has it ever been cleaned? If the tank accumulated trash over the years there could be sediment clogging the feed line.

StangStang

I pulled the fuel pump off and blew air through the feed line to the pump and the line to the carb. Both were obstruction free. I put the pump in a vice and manually pumped it. It felt good both on the pull side and the push side.

I fired the truck up after replacing the headers prior to pulling the pump and noticed that there was air pumping into the glass filter prior to the carb. It was very noticeable and I got video of it but not sure how to post it.

Possible that the pump is crack at a fitting and or air is leaking through the diaphragm?

Regardless the new one gets here on Thursday and I will try to install sometime this weekend.

67mustang302

Is this a new pump and the problem started when you put it on, or has it been fine and suddenly became a problem? Also, what size is the feed line to the pump?

StangStang

Yes, the pump was new and problem was immediate. Feed line is 3/8 hose. What is confusing is the air that is being pumped into the clear fuel filter.

I plan on installing the new pump on Friday. I will post results.

Thanks for the reply

67mustang302

You need a larger feed line. 1/2" AT LEAST, and not a soft rubber line, either metal tubing or the stainless braided Teflon so it doesn't try to implode and restrict flow.

Your likely starving the suction side of the pump and boiling fuel as it tries to pass into the pump. Once that happens and the pump starts to cavitate, it can't move fuel.

A 110gph pump is ****ing huge, and is intended to fuel n/a engines with 1,000+hp.