Hi all,

I am trying to finish wiring up a 2.9 L I put in '84 BII. The 2.9 is from a '88 BII.
When I turn on the ignition I hear the ECM relay, and the fuel pump relay. But... the fuel pump relay shuts off after about 2-3 seconds. Any ideas on this? I thought it should stay on.
I just installed the relay as well. It seems the old one blew up, along with my fuel pumps. I get good continuity and power to the harness. Just get that odd behavior. I will be replacing the fuel pumps both on the rail and in the tank in a few days when I have the money. Any insight on this would be much appreciated. Thanks.

Hawkeye

 

When the PCM first gets power, it will close the fuel pump relay. If it doesn't see the PIP (Profile Ignition Pickup) signal from the distributor within 2-3 seconds (to indicate that the engine is rotating), it will open the relay. No need to pump fuel to the engine if it isn't turning. Then, as soon as it sees the PIP signal (once the engine starts rotating as you start it), it will then close the relay again.

So what you describe sounds normal, unless the relay isn't closing when you try to start the engine.

 

Thanks for your reply. That helps. I'll have to check to see if it continues on with the key in start position and engine rotating.

Hawkeye

 

The FP relay is energized for approximately 2 seconds in order to pre-pressurize the fuel delivery system.

The PCM re-enables the relay when it sees an accelerating PIP signal which indicates the engine is firing.

The time intervals may overlap and provide a continuous operation of the pump if needed.

An important distinction from the above description.

Steve