Thread:

fuel supply issue

Having problems maintaining fuel pressure, pressure dropped from intial setting of 5psi to 3psi. Reset regulator to 7psi, seems better, but runnin home yesterday, lost all fuel pressure, with just enought to keep it runnig. I have a safety switch, on the motor for the electric pump, jumped the switch let it run for an hour with no issues with 7 psi. Im thinking the oil pressure switch is flaking out, the staked terminals are loose. Any suggestions for a quality switch? I'm running a Bosch relay for the pump power, so I should be good there.

That is probably your trouble. But let me ask. Why do you run it thru a oil pressure switch? So you don't have to remember to turn it on and off. Because if your doing it because you think or hope it will save you motor in the event you lose oil pressure, forget it. If the oil pressure fails, the motor will be toast before the float bowls empty. If you doing to stop the pump in event an accident, well, thats fine, but it is one more thing to go wrong, and its not exactly like a car where an accident could potentionally pump fuel on to the ground from a broken line.

It is for safety, and to meet the racing regs for electric fuel pumps, engine off/fuel off.
I can kill the power from the dash switch, and by pulling the lanyard. Am I getting too involved here?

No, I understand now. I can see where the racing org requires it. But having the power for the relay go thru that many different things will require that you stay on top of them or they could give you fits. We have had a coupe of oil pressure warning lights fail. They aren't real vibration proof. Now we replace it every couple years and save them as spares.

Ever consider a mechanical pump. The engine dies, the pump stops pumping. Its a pretty cool arrangment.

Yea, I would have a mechanical pump in a heart beat, but my Gen V block has no boss. I noticed I was low on fuel, as well, maybe two gallons in the stacker tank, is aeration a possiblity. Seems fine tonight, ran it for a couple hours. Still looking to get a better switch, than the Summit/Holley deal.

Doubt it aeration. Most likely vibration was causing a faulty swithc to not make contact often enought to keep the pressure up. If it runs fine bypassing the switch, its prbably the switch.
Running a GEN 5 is the only viable excuss for running an electric pump on any thing other than EFI.

Originally Posted by repoman

you can run a belt driven pump.bg makes one.

BG is right where he belongs, bankrupt and closed. Gone! Hopefully for good. You might be able to find one of his belt pumps a summit or jegs or. And when you need parts, you MIGHT be find them.

Aeromotive sells one as well. But the belt deal is a little bit if a pain.

My ignition and fuel pump were on separate switches on the dash. They both had separate relays. The ignition sw. also controlled the gauges, gauge lights and the launch control. The dead man would kill the ignition and fuel pump, but the dash and gauges would stay live as long as the ignition sw. was still on. There was only one wire through the dead man.

Originally Posted by repoman

you can run a belt driven pump.bg makes one.

I think then you're required to run a fuel shut-off. Most rules, anyway.

Originally Posted by sleekcrafter

It is for safety, and to meet the racing regs for electric fuel pumps, engine off/fuel off.
I can kill the power from the dash switch, and by pulling the lanyard. Am I getting too involved here?

If you're not required to have the pressure kill sw. then I'd eliminate it. If your lanyard kills the fuel, shouldn't that be enough?
Low fuel level can definitely cause pressure fluctuations. I remember my dad didn't have a fuel level gauge in our boat when I was a kid...he always new it was getting low on gas by the fuel pressure gauge. Never ran out that I can remember, but I do remember making some mad dashes to the gas dock!

Originally Posted by nelson#109

so you either ran switched power through the dead man, after the ign switch, and before the two switches; or you ran the dead man on the ground for the switched (trigger) power, before the two relays!!

So can I simplfy it a little..... Key off = fuel off, Lanyard pulled = fuel off, fuel pump switch off = fuel off.

All three would cover any situation, I can think of. What say you?