Fuel pump not priming.

[CutlassJim]

I'm having a problem with the Gaylant with the fuel pump not priming so the initial start takes forever.

The pump works great while the car is running and if I prime it manually with the test port it fires right up. I have been looking at the schematics and it looks like the ECU sends a signal to the power transistor to prime the pump. This never happens. I checked continuity and everything seems fine but I don't have a power tap tonight.

Any preemptive thoughts before I dig into it again tomorrow night?

 

[transparentdsm]

relay...... mpi

 

[FlyingEagle]

Um, from what I know of C53a turbo cars and likely C52a non turbo Colt/Mirages, the pump is only activated by a CAS signal to the ECU.
The ECU only starts the pump when this is triggered and keeps it running after that point.
The Galant is likely identical, because the 4g61 and 4g63 are managed exactly the same, for the intent and purpose of this comment anyways,
so you will not get a prime until the CAS sends out a signal. If the fuel system loses pressure and volume back to the tank due to the pump
check valve being inoperative, this could be your issue. Also if you are hot starting and it takes longer, the FPR solenoid is designed to
block off vacuum and create higher pressures to stabilize the hot fuel/vapor issue in the fuel rail.
Both possible candidates, but only above the fact that the pump only comes after a CAS signal comes into the ECU and the ECU triggers the
MPI relay to turn on the fuel pump.
I think I got all that right.

 

[jepherz]

The pump isn't supposed to prime from factory. It only runs with the key in the start position or when the CAS is sending the ECU signal. You can add a prime op to a new eprom, though, and keydiver did this for a few.

 

[Terry Posten]

The pump is controlled by the ECU and the MPI relay. There is a dual stage feature to this. The ignition key pops the MPI replay on for a brief few seconds to pressurize the rail. The ECU needs to see a CAS signal to keep the pump running after the inital start-up time period.

Swap in a spare relay first if possible.

Good luck.

 

[CutlassJim]

Terry has it right. I'll have to try another MPI if I can find one laying around.

For reference the MPI is the monster metal relay by the ECU correct?

I'll have to get a power tester on the ECU output to see if it's even trying to trigger the prime.

 

[Terry Posten]

Yes, goldish metal box under glovebox, next to ECU.

 

[FlyingEagle]

I stand corrected. Thanks guys.

 

[jepherz]

I'm confused, you're still looking for it to prime? Are you talking about it not starting when it's cranking? What exactly do you mean by "prime"? Is the pump not turning on with "start" in the ignition, or are you expecting it to come on when you turn the key to "on"?

 

[transparentdsm]

Quoting transparentdsm:
relay...... mpi




does this not count as being right?

i thought i was pretty on top of that....