dutchcrunch

we do not know how he is wiring it. he said directly, maybe he went straight to the pump. there is a fuel pump fuse # 34 according to enthusiasts companion. i would check that if you wired directly.

darth

Dear Indycam

"If he is getting the motor to run with a jumped dme relay , he must be doing the jumper correctly ?" I didn't say he was jumping it incorrectly. The fact that the "fuel pump kicks in for half a second then stops" and not being intimate with the circuitry, tells me it must be getting a signal to turn off which I suspect is the 3rd lead. If a 2 wire jumper is used this suspect signal is eliminated. When I drained my tank I simply used a 2 lead jumper to keep the pump on continuously.

Bill

Indycam

Eh ?

rattlsnak

to confirm, is this on an 89 model? the pre 91 cars have a seperate alarm and lock module, whereas the 91 + cars have the lock and alarm modules combined into one under the pass seat.

Anyway,, on the DME relay..
pin 3 = batt voltage at all times
pin 6 = ground
pin 1 = batt voltage WHEN CRANKING. this feed is from the alarm module.
pin 5 = batt voltage when cranking. this feeds fuse 27 tip if equipped.
pin 8 = ground supplied by ECU, when it receives crank signal, etc.
pin 7 = 12 v output to fuel pump

check the above in that order and post your findings.

GeorgeK

Good info and interesting questions. I will pass them along to my mechanic. I will develop as I get info.
Thank you all so far.

GeorgeK

Update:
We have determined that the fuel pump draws far too much current. Is there a surcharge protection in the standard DME/Fuel pump circuitry?

Indycam

Does it blow the fuse ?
You have not said anything about any blown fuses so its hard to see how its pulling to many amps .

dutchcrunch

the fuse for pump is a 15 amp.

GeorgeK

No Blown fuse. We suspect there is a surcharge protection in the relay or DME (?). It is pulling too many amps that is a certainty.

Indycam

It pulls to many amps but does not blow a fuse ?
You are thinking maybe something else is watching the amps and shutting off the flow before the fuse blows ?

GeorgeK

Yes. Is there a surge/overload protection in the relay or is it related to a DME function?

Indycam

I have had the cover off of the dme relay and have not seen anything that would jump out at me as a amp check / control . But I can't say I looked for that . The idea that it might , makes we want to test .
I don't know how the dme itself would "see" the amps going to the fuel pump .
If there was a shunt in the wire to the pump and the dme watched the amps via the shunt ...
But I have never seen a shunt in a 964 .

rattlsnak

No, neither has any kind of surge protection... if it draws too many amps, it pops the fuse. period. did you check the pin outs as i posted earlier? It sounds like your guy is chasing his tail. if you give us the readouts from the pin outs, we can further help you.

GeorgeK

I doubt he is chasing his tail, because he is not paid for that work. And he very much knows these cars.

Anyway, I will not access the car until saturday, so I have phone talks with hin only now. I pass on the info as I get it, both ways.

I'll update as it comes.

Indycam

When you jumped the dme relay and the pump ran and the engine kept running and no fuse blew .
That makes me think that the pump was not pulling more amps than the fuse could handle .

I wish I was there .