I had replaced the fuel pump last christ.MY car is doing the same thing it did last year.3 mechanics told me that a bad inition module could keep the fuel pump from coming on.IS this true?The injectors are not fireing,but I thought when you turn on the key,you should hear the pump for about two seconds.This on my 90 Firebird 305 tbi.

 

The pump should run for 2 seconds when the key is first turned on. Check the fuel pump relay.

the module will keep the pump from coming on during cranking if its faulty, but the 2 second prime when you turn the key to the on position is automatically done by the computer.

 

So if the car was already running it won't prime after dying?

 

To get the fuel pump to prime again after it dies (stalls) need to turn the ignition off for 5 seconds or more, then key back on. The pump should again run for 2 seconds then shut off.

Once the ECM sees distributor reference pulses (DRP, from the ignition module), the ECM will turn on the fuel pump. The pump should stay running for 2 seconds after the last DRP is seen by the ECM.

IOW, key on, engine off, and the pump runs for 2 seconds thens stops.

A short crank of the engine (not started or running) and the pump comes on again, runs for 2 seconds, then stops.

Once running the ECM keeps the pump on as long as it sees the DRPs. No DRPs, no fuel pump (after 2 seconds) and no injector pulsing.

If the engine is cranked long enough to produce some oil pressure, the bypass switch closes and turns on the fuel pump. This oil pressure switch does not use the relay. It is a backup system for a failed relay.

RBob.

 

well I tried it today and the pump never primed at all.No fuel and no injectors firing.Maybe an inition module?Fuel pump is only a year old.I tried a new relay allready and no luck. NO codes either.Last year I had a lean code and we checked fuel pressure and the pump was going out.what do you think?

 

Ignition module has nothing to do with the key-on 2 second prime. That is the job of the ECM and fuel pump relay. Not sure on the MY but some/most? have a red pigtail that is in the wiring harness. This can be connected to battery+ in order to run the fuel pump.

It is for testing purposes. it bypasses the relay so that the pump may be tested. I would do that, and if there isn't a pigtail, I would remove the relay and jumper battery+ there.

Basically you want to run +12 volts (from the battery) directly to the fuel pump. That eliminates everything else from the equation. If it doesn't run, then it's the pump. If it does run, then it is either the relay, relay socket, wiring, or the ECM.

RBob.

 

Well she is running.I replaced the mod and cap and rotor.She has a miss but not a bad one.Maybe a wire in the wrong spot,but i will check that out when light gets here.