Ag02M5

Hi.

I have found bits and pieces both here and in Adrian's book but wanted something more comprehensive and specific to a 964t.

What I know for certain is that the car has 2 fuel pumps. One in the front of the luggage compartment and the second on the passenger side in the engine compartment.

They are controlled by relay 61 on the far passenger side of the fuse box. Also, fuses 26 and 27 are pump related as well.

With that said, what is the proper/normal operation. Do both pumps come on at the same time and always work in unison? I.E. should I hear both before the car fires and should both always be on while the car is running. Or are there times when one is on and the other is not? If so, what scenarios?

The next question is how do you properly jump the relay to test their operation. Should both come on or are they controlled independently by the relay and require separate jumper settings of the 4 pins on the relay.

The last question is when do they have juice? I'm guessing in jumpered mode would be the easiest time to test power going to the pumps. It seems in normal operation, with the key in the ignition you hear the pumps and then they shut off (assuming you don't turn the car on). Therefore to check the juice (assuming you can't hear it), you would have to check it before the relay cut the power.

Once I can eliminate the fuel pumps, I will move on to fuel pressure.

Thanks and please feel free to add anything I may have missed.

RT

Ag02M5

Not to jump the gun, but I somewhat accidentally jumpered the rear fuel pump and I could hear it run. However the front did not start up with that jumper setting. I could not find a configuration where the front pump ran by guessing.

With the relay back in place, I did turn the ignition to 'on' and heard the front pump running. I ran around back and not a sound from the rear pump.

So now back to my question of normal operation. When should each of the pumps be running (pre-start and engine running)? Battery is now dead so running tests will have to be tomorrow.

Cheers.

RT

Ag02M5

Bueller...

Guess everyone took the weekend off from posting.

nathanUK '81 930 G50

On a 930 both pumps work together. Never one on its own. Pumps only come on while cranking or engine running due to a switch on the CIS metering plate.
If you want to bypass the CIS simply remove the connection to the air meter. Pumps should then run constantly when the ignition is on.

I didn't post earlier due to this info being for a 930. Hope it helps.

Ag02M5

Thanks.

Can anyone confirm that a 964 operated in the same fashion?

Thanks.

RT

porschedude996TT

I would suggest tracing the electrical schematic.