BAD91CamaroRS

Problem: Fuel pump primes, start engine runs for a few seconds untill fuel pump relay kicks off and stops fuel flow to the carb. Once the float bowls get sucked dry I have to wait a while and reprime the system and start again or take the 20amp fuse in and out (fuse by passenger side by the battery)... That seems to be the only way to keep the car running is to push the fuse in and out while the car is running in order to keep the fuel pump going. Car has a Carb'd 383.

Anybody have any ideas of what could be causing this... AND I already put a new fuel pump relay in.
Thanks,
Brian

BAD91CamaroRS

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camaronewbie

Maybe a bad oil pressure sending unit (OPSU). Once the pump primes through the relay, then there is no more current from the relay to the pump - the current comes directly from the battery through the OPSU to run the pump. Try jumping the pump directly (at the relay) and see if the pumps runs continuously - if so, may need a new OPSU.

FYI - If you've gone carb, you can remove the ECM, and the pump won't prime at all - BUT you must have enough oil pressure to make the pump run from the OPSU. My carbed 350 is set this way - if I leave the car without starting it for more than a week, the oil pressure will not raise enough to run the pump before the battery is dead from turning the motor over so many times (all oil drains completely into pan and can't get pumped enough to connect power at the OPSU to run the fuel pump).

BAD91CamaroRS

Well the OPSU must be good because the gauges show the oil pressure... Does anybody have a diagram of how to jump the pump at the relay?

BigBadLou

iTrader: (3)

The OPSU has two parts: an oil pressure sensor and oil pressure switch. The switch could be bad while the sensor is good.

Also, the problem might be in the wiring to/from the OPSU. You can test that by pulling off the OPSU connector and shorting the orange and grey wires (with a paperclip or something). If the pump runs, the wiring is good.

Hope this helps.
Lou

camaronewbie

Actually, the guage itself gets input from a totally different oil pressure sensor in the driver head. The OPSU is located usually above the oil filter (sometimes on the china wall behind the intake close to the distributor on a 'T').

A bad OPSU can also kill your battery, by making the fuel pump run constantly, regardless of key position, car off/on, etc. It takes about 2-3 days of not starting the car for the battery to be drained by a constant fuel pump running (ask me how I know lol).

BigBadLou

iTrader: (3)

Oh true, I forgot he didn't have the stock engine anymore.
On the 383, who knows if it even has the OPSU. It might not be there which would perfectly explain the behavior.

Lou

BAD91CamaroRS

I'm still confused about this oil pressure sensor and switch since the car is 15 miles away from my house where im on the computer at... Anyways, the sensor which is usually by the oil filter has been moved to the china wall behind the intake instead. That has been replaced a year ago and hasn't given me a problem since. Now this switch that you guys are talking about is not ringing a bell at all.