Perry 951

Need some help. I am missing the DME harness pinout page from my manuals.

I need to know what color wire, and what pin, for the positive power supply to the fuel pump from the DME. If I am correct, the fuel pump will not run if this wire is disconnected.. right?

TIA!

IanM

Hooking up a kill switch? That's what I did. Be careful though, as eventually this caused me grief, and was the source of my dropping fuel pressure under boost problem. What I ended up doing is sending the power from the fuse box into my switch, then out of the switch into a 30 amp relay. Then I took a 10 gauge power lead straight off the battery into the relay, then out of the relay into the pump used the stock fuel pump power lead. This way you avoid sending lots of current through your kill switch. If I remember correctly, the fuel pump power wire from the fuse box is green/black. I'll have to check out my wiring diagram again and get back to you regarding fuse box pin numbers.

Sorry...you asked about the power lead out of the DME. I also have the wire and pin info on the lead coming out of the DME into the fuse box, but I'll have to get back to you on that too.

Perry 951

Bingo, no fuel, no stolen car.

I was going to tap the main power lead at the fuse box, but decided it would be better, and cleaner, to splice in at the DME harness.

One of my concerns was the current flowing through the switch. A relay would be better, but I am a goof when it comes to stuff like that. If you could lay a diagram on me, that would be very helpful.

sm

IanM,

I would be interested in your diagram/explanation as well. The car doesn't have theft insurance and is parked in Brooklyn <img border="0" title="" alt="[Frown]" src="frown.gif" />

IanM

I still need to go home and check the wire colour and pin number, but here's a quick rundown of how to wire things up.

- Cut green/black wire coming out of fuse box that goes to fuel pump.

- End of wire coming from fuse box goes into your kill switch.

- Out of your kill switch goes into terminal 86 on relay

- From terminal 85 on relay goes to ground

- Connect 10 gauge wire from battery into terminal 30 on relay

- End of green/black wire going to fuel pump connects to relay terminal 87

sm

Do you simply unscrew and lift up the fuse box (the one in the engine compartment?) to reach the said wire?

Badue

Pin 20 on the '86 DME is the wire to the DME relay. I'm pretty sure on most of them it is pin 5 on the 14 pin connector by the brake booster. Put a switch on that wire and you dont have to worry with relays as you leave the power circuit to the fuel pump unaffected. It should be a black/gray wire. It looks like on the diagram that there is a loop of this wire that goes into the cabin possibly for a planned addition of security system in later years. I dont know where that loop is.
That wire is the ground circuit for the fuel pump side of the DME relay. If you keep the computer from grounding this wire by opening the circuit it will not run. Unless your planning on adding an extra relay anyway for more stable power to the fuel pump, this is the easiest and safest way to do it. I am adding an additional realay and a larger fused power feed to the battery to give my pump more power. (Less voltage drop than stock)
My sugestion only requires two wire and a switch. They can even be a small guage speaker wire pair. Easy!

Perry 951

Excellent post! That is a great solution. I did not think to switch the ground.

I have to run new wires for my MAF, so I'll pull 2 more along with it to run along the firewall.

Thanks guys!

nine-44

Remember kids, brown is always ground on P-cars.

Danno

Hmmm, you could also use the existing kill-switch used by the factory alarm. It not only kills power to the fuel-pump, but to the DME as well...

Perry 951

Danno -

Doesn't the DME have some fuzzy logic in it? If so, wouldn't killing the main power for it erase the info?

I thought about this very thing, but went against it. My father did it to his '84 Turbo Z, and it would always run like crap when he used the switch. That ECU had a good amount of fuzzy logic, and would have to learn again.

IanM

Perry-
If you want to use the power lead coming out of the fuse box and into the fuel pump, it's a black w/ green wire, pin number F25 out of fuse box. Disconnect battery, unscrew fuse box, pull out through top, find wire, cut, solder in extensions, relay etc.

If you want to use the power lead going from the DME to the DME/fuel pump relay, it looks like it's a grey/black wire, going into pin N43 on the fuse box. The loop that Badue is talking about looks to me like a yellow/black wire, runs outside the fuse box from pin M42 to pin M13. Don't quote me on these ones though, as I didn't go this route myself so I can't 100% confirm. This part of the DME circuit confuses me a bit. That's why I went the other route. Plus, it's nice having a relayed big fat power lead straight from the battery going to my upgraded fuel pump.

Good luck!!