First question...does anyone have a good wiring diagram for an '84 and where can I get one. The '84's are different than other years, and even the colour coding of the wires does not always match the '86 workshop manual that I have.
Here is what is going on. I'm doing a V8 swap in what was originally an '84 4cyl auto car. I pulled out the harness that runs from the computer to the engine compartment. This is the one that has 2 connectors for the computer and 2 others that attach to the harness in the centre console (running forward to the instrument panel I assume). There is another large harness that runs from the inside of the car, out through the firewall; this one has 2 large plugs on it in the engine compartment. One of these plugs connects to a harness that seems to come from the drivers side of the car, just forward of the wheelwell area. This harness has 2 relays on it, that if I remember right, mount on the firewall. I think these are the relays for the fuel pump and the A/C.
So getting back to the harness that I removed (the one from the computer). Since I've got a carb, I'm pretty sure I don't need the computer, so I decided to strip all the wiring out of this harness that goes to the computer. This also makes the wiring bundle that passes through the firewall reduce from around 30-35 wires, down to 8 wires. Since I'm moving this pass-through over to the drivers side, I won't need as big a hole in the firewall. OK, so if you have followed all this, the harness that I've stripped the wires out of, that used to connect to the computer, now still has the connectors that connect with the centre console wiring, the diagnostic plug is still on this harness (but doesn't have many wires left and I likely don't need it anyways), the plug for the oil pressure sensor is also on this harness, and finally, and now we have come to the question....there are 2 relays on this harness...what are they for??? I can't remember where they were mounted, but pretty sure it was the engine compartment. One of them seems to tie into the oil pressure sensor, so I'm wondering is it is something to prevent the fuel pump from running if there is no oil pressure? Is there a system like that? I've looked through the wiring diagrams that I have and can't find what these 2 relays are for.
So if you are familiar with the wiring of '84's and you have followed all this, can you tell me what these 2 relays are for, and is there a decent wiring diagram available somewhere.
I have the shop manual ffor the 84 model if you want to look at it, there is four relays on an 84 if it has A/C. Two are for the tail lights to make the signal lights and brake lights work properly which is only the 84's that have these two relays. The other two are for fuel pump and A/C. The C203 and C500 are wired different as far as the speed sensor, the A/C and a few other things go and the 84 has the battery power going through two seperate pins on the C500 where the 85 up use the little junction block below the C500 for this. Dan
IP: Logged
08:59 AM
Mike Gonzalez Member
Posts: 5093 From: Colorado Springs, CO. USA Registered: Jul 2001
The Relay that seems to go to the oil sender is the fuel pump relay. The oil sender is a backup switch to turn on the FP should the relay fail. The othe on that harness should be A/C.
IP: Logged
09:05 AM
couldahadaV8 Member
Posts: 797 From: Bolton, Ontario, Canada Registered: Feb 2008
Thank you very much for the help guys, that is great. So the 2 relays that are on my harness are actually the fuel pump and A/C relays. The 2 that are still in the car, attached to the large harness coming from the drivers wheelwell area are the tail light ones. This makes sense now. My oil pressure sensor connector does have 3 wires coming from it, which I thought was a bit strange but your wiring diagram does show this, and it does go to the fuel pump relay.
thanks again for the help,
Rick
[This message has been edited by couldahadaV8 (edited 10-05-2009).]
IP: Logged
09:33 AM
couldahadaV8 Member
Posts: 797 From: Bolton, Ontario, Canada Registered: Feb 2008
This is interesting. Looking at the wiring diagram, I don't even need the fuel pump relay since the oil pressure sensor wiring is basically bypassing it. I also have lost the trigger wire for the pump relay in removing the computer ("fuel pump relay drive", connection 10 on the computer), but I suppose tapping it into something like the ignition wire (hot for "start" and "run") will work fine.
I've also lost the trigger wire for the A/C relay in removing the computer, but again any wire that is hot with A/C on should work fine.
The fuel pump will run once you build enough oil pressure that way but you will be cranking for a while to get it, I would run a wire off the ignition switch or right from the small purple wire at the starter so the pump primes while cranking the engine then the pump should continue to run once the engine starts and builds pressure. The 84 harness already has an extra wire from the starter that fed the ECM that you can use. For the A/C you do not need the ECM just use the +12 volts at C203 pin D which comes from the front A/C pressure sensor, use this wire to control the A/C compressor relay and you will be fine. Dan
