I have a streetrod with 351w, edelbrock intake and dual quads. Driving down road it suddenly acted like it was out of gas and quit. In a bit it would start up and run ok . A couple times it has stumbled at low speeds. I finally figured out it was intermittent fuel problem of some type. Tonight I had it idling in garage and watched fuel pressure go from 8 to 3 and then back up in a few seconds over and over. Im not sure if the gauge is liquid or not, but the engine does react to it so I think the pressure problem is real. Gauge is next to carb so I cant watch it while driving. The car has new steel tank, 3/8 steel line ,electric pump, and filter near tank. I have it set up with oil pressure safety fuel shut off. Does this sound like a pump problem? Filter problem? fuel pickup ? Not sure how to proceed.
Is there a regulator in this system somewhere or are you just using the electric pumps output ? If the filter is able to be taken apart, I'd start there and see if you have some sort of restriction or plugging.
After checking for junk in the lines, I have to ask... what is the pump rated pressure? If it were me I would be running a pump a little higher than needed and a regulator at the pressure I wanted. It sounds like the pump is either intermittently clogged or on its way out. If everything else checks out, probably a bad pump. Next one, install a filter before the pump and a pressure regulator after, close to the carbs.
There's several things it could be- But if the car reacts to this pressure fluctuation at idle - I'd first be looking at the systems voltage. The engine would react to a surging voltage and cause the pumps out put to vary Inorder for the pump to have a consistent and steady output, The pump needs (must have) several things. Consistent voltage, consistent fuel supply. It's easy to eliminate the possibility of a vent problem- take The cap off and observe. Then test the voltage and see if the voltage surges with the pump pressure.
Is the pump wired through a switch? If so, rewire through a relay. It wants a steady supply with a big wire.
sounds like a electrical issue or location issue with the pump . you should be able to hear the pump change tone unless its a facet type , we run a fused hot lead back to a relay near the pump from the battery and use a circuit to control the relay so no high amp load is carried thru switches which will cause a intermittent voltage reduction when they get hot . if not that is your pump inlet as low as the bottom of the tank and next to it ?? as pumps do not like to try to pull fuel from the tank and will surge when doing so .when its level with the bottom of the tank it will act as a siphon when it gets going.
Just tried w/o cap - same thing. Pump and filter next to tank (low). It is run through a relay from fused wire. Dont know offhand the pump rating, no fuel pressure regulator - thought that was mostly for injection systems. I havent checked voltage. Very intermittent problem, sometimes it drives great with no issues, the other times it can unexpectedly stumble or quit. I really appreciate the imput.
what brand pump ?? also what amp/ brand relay , as they do make them in 20-70 amps and a small one will burn up the points in it real quick if its under rated , only good relays I find are either bosch , or any borrowed from a latemodel Gm or ford EFI car . have run across some supposed 40 amps at warzone that burned up with 5 amps of load
Well intermittent problems are tough- almost every test you can think of will pass when it's not exhibiting problems "you can't fix it if its not broken" fits very well because you can't find it. The absolute best way to find an intermittent problem is to catch it while its fucking up. That usually means adjusting yourself to being ready to test it when it's ready to fuck up. Having some test gauges hooked up while driving is a good one.
8psi is too much for Edelbrock carburetors. Get a regulator, and set it to 5psi. Anything higher than that, and you risk pushing the float needles, and flooding. It says 5-1/2psi in Edelbrock's own literature. That is the absolute maximum, I have observed.
No name on pump or receipt from 7 yrs ago (bought from local hotrod shop). Filter is near tank outlet - then pump near bottom of tank. Bought all my relays from M.A.D. electrical and I believe all his stuff is high quality Bosch, but I dont know amp rating. First time it quit was last fall and since then I made a troubleshooting check list with a jumper wire to carry in hopes of isolating problem if it quits on the road. Hasnt quit since but almost. I will get a pressure regulator but not sure if thats connected with my current problem. Where should I test voltage - right at pump?
Had brushes go in a Mallory 140gpm pump many moons ago. Very similar symptoms. Fortunately brushes were available so was a pretty easy fix. Posted using the Full Custom H.A.M.B. App!
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