Fuel pressure problems

[Tim Brewer]

I have had idle problems lately, and one thing I've noticed is my Mallory regulator will never remain constant. I've set it to 7lbs. But sometimes it will show anywhere between 0 and 14 for no reason at all. I have a Mallory series 140 pump for fuel delivery. Do I have a bad regulator?
Thanks, Tim

[davidlee]

I have a Holley reg and have the same type of problem. I set the reg at 7 lbs. check it later and it is at 3lbs. I use a liquid filled gauge and have heard somewhere that they may be inaccurate when they heat up from the engine. When the engine bay cools down the pressure returns to 7 lbs.
David

[Cobra20646]

I have to agree with David.... I went through two of the liquid filled gauges before it dawned on me that the gauge was not working accurately. Replaced it with a 'normal' air filled gauge and no more problems. As David said, underhood heat caused them to fail.

[Tim Brewer]

Wow! I guess I'll change over to a air filled gauge and see if thats it. It does make sense.
Thanks guys,
Tim

[CJ428CJ]

Hmm, I've had similar problems. I have no pressure regulator but my liquid filled gauge will show about 7 psi sometimes but often drops to 0. I thought it was the gauge (Summit brand) so I swapped it out for another brand liquid filled (Earls) but I get the same result. Maybe it's time to try an air filled type.

[HighPlainsDrifter]

Hi,
I've found that the fuel line from the tank to the fuel pump will collapse and starve the fuel pump causing the needle to bounce from 0 to 7 psi. The way to cure it is to put in a metal line ,you can use short rubber lines to secure it as they aren't long enough to colapse with a high output pump sucking on it.
Good Luck,
Perry.

[CJ428CJ]

I've got steel lines except for about a 2 foot piece between the fuel tank and the start of the steel line as well as steel braided between the mechanical fuel pump and the carb. I'm pretty sure the problem is gauge related because even though the gauge reads 0 psi much of the time, the car runs great and never has a stumble or miss that you'd expect if a fuel line was collapsing somewhere. I'll either switch to an air filled gauge or remove the gauge entirely and just not worry about it since I'm not having any performance problems.

Chris