924 fuel pump wiring

jmk2222 · 06-01-2009, 08:04 PM

If anyone has experience with the fuel pump wiring on an '81 924 NA please help. I put new pumps in because the old ones had frozen from sitting with old fuel. Car will run on starting fluid but nothing from the fuel pumps. To make a long story short, got to the back of the fuse/relay panel and found the black/green wire that is power to the pumps. When I put 12V to it, I can hear the pumps run. According to the current flow diagram, this wire runs directly from the DME relay to the pump, but that is not so. The wire from the DME is red/white and runs up under the hood somewhere, so the connection to the fuel pumps is being interrupted somewhere under the hood, but WHERE?? Please Advise....

924RACR · 06-02-2009, 05:16 AM

There is no DME, so no DME relay.

Sounds like you need to learn to read the wiring diagrams (which i think Pelican has archived around here somewhere in full color?).

Not sure about that year, but it may be that you have to have a signal from the coil to actuate the fuel pump relay?

I trust you purged out all the old fuel and flushed the lines??? Otherwise you're gonna follow up your expensive pump purchase with some even more expensive CIS components...

jmk2222 · 06-02-2009, 01:05 PM

Then I should take my DME relay and throw it away!!

I DO know how to read the wiring diagrams there wiseass but the problem is that pelicans diagram is for a 1978 not a 1981, which is obviously slightly different than my car.

Could someone that actually has a clue answer my question and NOT the last guy!

Razorback1980 · Razorback1980's Garage

Easy, I am sure Vaughan meant nothing derogatory. I didn't think they had DMEs either but I'm not real familiar with the 924. Probably best to check on 924.org.

924RACR · 06-02-2009, 04:08 PM

Wow, excuse me all to hell for trying to help you.

I'll trouble you no further... prick.

JonA · 06-02-2009, 06:27 PM

Get the Haynes manual for the 924. It is surprisingly good with additional schematics for 81-82. You can jumper the fuel pump relay from 30 to 87 to get things running. There is also a 16 amp fuse (#2) in the add-on fuse board for the pump.

Jon

Buwani · 06-02-2009, 06:35 PM

Nice attitude directed to a guy that has more knowledge of the 924 that you would ever hope to have.

What you THINK is a DME relay is the fuel pump relay. Not the same thing. Yes it does disappear under the dash, it even changes wire color.

I would look in my diagram for someone else.
Tool

Shawn

jmk2222 · 06-02-2009, 08:08 PM

Sorry if I took your post as a bash on me. My terminology is off, alas no DME, I'm used to the way it was on my old 944. I tried jumpering the relay already and no juice to the pump, but when I supply power directly to the black and green fuel pump wire under the dash the pump runs. I'm just trying to determine what under the hood is breaking the circuit. What would be the downfall of hooking the fuel pump feed to the 87 pin? I assume its some safety feature to keep the fuel pump from running in case of an accident, but if its something else let me know. Once again sorry for being an ass, just frustrated trying to get this thing to run properly and undo the hillbilly job that the previous owner(s) did on it.

924RACR · 06-03-2009, 04:59 AM

OK, thank you. I wanted to make sure you are addressing this problem correctly, and are aware of the components with which you are working. We always try to correct when, say, people come in looking for a chip for their '79 924 - instead of just selling them one!

Hey, where did that spam come from???

Yes, the black green wire goes to supply power to the pump from the relay. There is indeed a little fancy circuit in the fuel pump relay, takes a tach signal on the green/green-white wire (should have continuity to the "1" terminal on the coil) to turn that on. If that wire has no connection to the tach signal, or the circuit is bad - no power for the pump. Ground for the switching circuit in the relay is the brown wire, per the usual.

The relay also gets power on the black wire from the ignition on circuit (#15). The actual pump power comes to the relay on the red/blue wire, which is straight from the battery, unfused, unswitched. It goes out on a red/black wire to the #2 fuse on the aux fuse board, then comes out on the black/green wire. There is also a red/white wire, the one you're looking at, goes under the hood to power the warm-up-regulator and aux air valve. There's also another black/green wire going under the hood, powers the freq. valve for the CIS (Lambda adjustment).

So, the engine will need to be cranking and have a good tach signal going to the relay before the relay will turn on.

An intermediate step would be to put a jumper between the 30 and 87 terminals of the relay, that should power the pumps if all the rest of the wiring is OK. This would be a worthwhile test - verify wiring between the relay and the fuse is OK.

Then it's a matter of determining if the relay or the tach signal is bad; verify continuity to the coil of the #1 (green wire) terminal. If it's good (and assuming you have power and ground for the relay at terminals 15 and 31), then you likely have to buy a new relay (assuming the pumps run still when you jumper at the relay socket).

Good luck...