I am running an in tank pump and Mallory return style regulator on a drag car. Normally everything appears to be fine, pressure holds at 6 1/2 PSI and is stable. There are times though, when I look at pressure after a run and see gauge needle at 3 PSI. Is this a sign of a bad pump? Car is running good times, no real sign of fuel starvation. After car sits awhile, pressure returns to normal 6 1/2 PSI.

Any ideas?

Hmmm...me thinks the pump may be a bit low on the volume side. 3 PSI at WOT is OK...but it should just about immediatley shoot back to 6.5 psi.

What type of pump is it? Me thinks you're making enough HP that you should invest in a good Baryy Grant or Mallory electric fuel pump. Time to upgarde the fuel line as well. 1\2" ( aluminium ) all the way from tank to carb...or at least to the fuel log. Big Fram fuel filter as well....


Fram HPG1

Edit: Regarding Fuel Filter. Put it in just before fuel log. You'll probably have to neck adapter down from 1\2" ( -8 AN ) to 3\8" ( -6 AN ) to fit fuel filter. If you want to go whole hog, Barry grant makes some fuel filters that have 1\2" inlets and outlets and also 1\2" fuel logs. Don't think that is really necessary though. You really only need the 1\2 line from the tank to the Fuel filter. Reduces volume and pressure loss for the pump.

Looks like you'll have to update your signature again....

Is always after a run. Fuel bowls are full. Maybe vapor lock after shutdown? Gonna shield fuel lines.

interesting, mine will fluctuate too, but only about 1-1.5 psi, and doesn't have much of a pattern to it. I use the same set up. I'd like to hear some suggestions.

It does not seem to be a problem until driver gets back to pits and stops car. I think it may be heat off headers warming fuel lines. I have him get in and start pump and gauge only shows three PSI. After car cools, shows 6.5 PSI. I checked a couple times before he shut off engine and was 6.5 PSI. Float bowls are always full, before during and after. Am installing pressure gauge at windshield and adding separate pump lines to bowls.

Have you wrapped the fuel lines in a heat shielding of some sort?

Am going to. Have material ordered. Currently fighting with rollbar install. I do not bend the way I used to. PITA....period.

Car is now hovering at next safety rule cutoff. .03 of a second slower than rollbar for IHRA (7.49 1/8th mile). That was with foot on brake trying not to break out. Went 7.52 against 7.58 dial in. Cannot run again until legal with 8 pt bar. Already not legal for NHRA, 11.99 (1/4 mile) or faster must have bar. Driver (son) is 6' 7" tall, makes it even more of pain as bar must fit him and his Mommy who is 5' 7" tall. Mommy wants to take car for a few passes. May go faster, she is only 127 lbs., son is 220. She is also fearless with gas pedal.

I am having the same problem,

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