bobzdar

I just picked up an '86 944 and I have what appears to be the fairly common no-start issue. However, mine appears somewhat unique in that it's not the DME relay, DME or fuel pump. The car runs fine if I jumper the 3 DME relay pins to turn on the fuel pump and DME. I put in a different DME relay from a running car and got no start, so it's not the relay.

I probed pin 86 which I think is the signal for the DME portion of the relay and just get a constant .3v whether the car is on or off indicating to me that something fried in the wiring. However, I can't find a wiring diagram to find out which wire is feeding it from the bottom of the fuse box and where that leads to. I did find a burned up wire and I cut what was left of it out as it was a fire waiting to happen.

I'm tempted to just manually run a wire from a switched ignition source right to the DME relay and bypass whatever is causing the issue, but I'd like to at least attempt to fix it properly first. Any ideas on what could be causing the DME relay to no longer get a signal from the ignition switch? Any links to a wiring diagram?

Other than that issue and one buzzing relay in the cooling fan relay box, the car runs very well and everything except the power door locks work (though it seems like they try to work at least).

951Saga

Here is a link to the Workshop Manuals, texasblake.com, load Volume 4 then go to section 97 sheet 7 for the engine compartment wiring diagram. You can print the pages and tape them together for a better view.

bobzdar

Thanks, I spent about half an hour last night looking for that. I'll see if I can sort it out this evening.

StoogeMoe

The DME sends out a signal to the DME relay when it thinks the engine is spinning. This turns on the fuel pump. It's really just a safety issue. If you ever got in an accident, and a fuel line got cut, you would want the pump to stop if the engine stopped. Otherwise it could pump gas all over your hot engine while you're unconscious in the car and burn you to a crisp.

I think a lot of cars have that line jumpered to the ignition switch. Because I see posts that say their fuel pump turns on when they turn the key to on. This will work, but circumvents the above safety function.

I don't have my FS manual in front of me to tell you what wires to trace. You may have already figured it out.

bobzdar

It looks like the line from the fuel pump relay to the DME was already shot before I got the car as the PO had manually closed that relay. I ended up modifying the relay to turn the fuel pump on when the ignition turns on (just grounded the relay coil to the same ground as the other relay) and ran a new wire to the DME relay from an ignition hot wire. The car runs fine now but I'm not too keen on the fuel pump running whenever the key is hot for the above mentioned safety reasons. I'll have to see if the pin on the DME itself is operating correctly and if it is, just run a new wire from there to the fuse box.

I did find another issue when running through a final check of the car prior to getting it inspected, and I'm a little stumped. The high beams work when the switch is pulled to flash them, but the lights just shut off when it's pushed to turn the high beams on and leave them on. I checked all relevant fuses and swapped the relay for one of the other ones, but nothing seems to work. Any ideas?

Dr. 914

I would just buy and install a new relay and look at the back of the fuseblock where the square plug plugs into the fuse block to make sure that all of the terminals are up to the top of the plug and that the plug is clean and corrosion free