I am having difficulties with my fuel pressure - it's slowly going down over a period of 30 minutes or so and eventually drops to 0 and the car dies. It's carbureted with an electric fuel pump (pusher at the back of the car). There are no leaks and the fuel cell vent is good. I changed fuel pump (Jeg's billet 120 gph) to an Edelbrock "ultra quiet" 120 gph one. (Virtually identical). I replaced the pressure regulator with an aluminum block to eliminate that. The block is at the front frame rail and it's all AN8 to the block and AN6 to the carbs. The flow eventually just stops. I have checked the fuel filter (cannister type before the fuel pump), fuel pump relay, fuel cell pickup, vent, and no leaks. Cold it hits 6.5 psi but slowly drops to 0 in about 30 minutes of running. The fuel lines and fittings reach around 120F all heated up. I can crack the outlet of the fuel pump to get flow again, but gas free flows from the block with the pump off if the fittings are disconnected there (pump off). No flow there when it's acting up. This one has me stumped.... Yes, the car has gas in it. Thanks for any help.
Yes I know you said your vent is good but Check to see if you have a vacuum in your gas tank by releasing the cap. Also try isolating your problem by by-passing the filter and fittings. Run a direct hose from the pump to the carbs also try a direct hose from tank to pump.
Thanks - did that and there was no vacuum, I even left the cap off (before I checked the vent tube) and it still quit on me.
Not a fan of the cartridge type filters before the pump , try pulling the element & run w/o ....1 change at a time.... dave
By pass that filter. I had a filter just like that years ago, and it caused problems , and they tend to leak at the o-ring after time.
Is the pump pulling fuel through the big filter? Possibly the pump is pulling fuel fast than the the filter allows.
It sounds like the pump is cavitating after a period of time. Since it appears that you are not running a bypass regulator, the fuel in the pump just continually increases in temperature to the point of vaporization. This would especially be the case at low demand flow such as idle. At that point the pump is just cavitiating until it could cool down a bit. A bypass regulator allows continual flow thereby keeping the fuel a bit cooler at all points in the system.
Does that pump have to be mounted up or down, years ago, had a blue pump (cannot remember brand, Holly?) and I mounted it like yours looks (for clearance) and turns out that is upside down and pump got hot, did not pump fuel, cool off and work. So.... replaced w/ new pump, same one, same result, called mfg. And was told to turn pump over, DUH, guess I should read instruction's carefully something I learned over the years the hard way.
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