Quote:
Originally Posted by Breezio69
Ummmmm... My pump primes (turns on) when my key is in the on position just before starting. As stated, it "primes" the system up to operating pressure, because when your car shuts off the pressure from the fuel system slowly drops off back in to the tank (hence the fuel return line)
Sounds pretty normal, maybe you just never noticed or the pump got louder because its going out?
And once the pump is on, its on, it will just sit and whine... it doesnt shut off then start, then shut off and start while the car is running or in "on". It is constantly on once you turn the key to on or start it
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That may be how yours is working but that's not how it's designed to work based on the diagrams, tech manual, and observing 1G's and 2G's over the years.
Since the OP is asking about a 1G I won't talk about how 2G's are different. There are threads on the site the cover both and the differences.
On a stock 1G the fuel pump is controlled by on half of the MPI relay and there are two inputs, a signal from the starter circuit and one from the ECU.
The idea is that when you start cranking the engine the starter circuit will turn on the fuel pump and then once the engine started running the ECU will keep the fuel pump running until you stop the engine or something else does.
The starter side is simple, the same 12v signal that drives the starter solenoid drives on of the coils for the relay. When the starter is running the relay is activated power the pump. Stop cranking the starter and the pump stops.
The ECU side is a little different since the ECU switches the ground side of the relay coil not the 12v side. When the ECU sees pulses from the CAS is turns on the fuel pump and once it stops seeing CAS pulses it stops resetting a counter which decrements to 0 after a few seconds and the ECU turns off the pump.
So the first question is which of these two signals are turning the pump on or is the MPI relay borked? Get the multimeter and wiring diagram out and start measuring the voltages at the MPI relay. The rest of the diagnosis follows from there.
