please someone help me with the engine wiring

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illregal82

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Jul 4, 2006
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i am in the process of a 3.8 to 350 swap is there any where i can get a free wiring diagram of what wire is what under the hood of my car so i know what i can get rid of and what i need to run my car i so am tring to drive it before it snows here please help my freind helping me (he does all the work) is comig over to try and finish up today but he has been saying that forever it seems
 

pontiacgp

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Mar 31, 2006
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if your not using an ECM then all you need is the wires to the starter, battery, alternator and distributor
 

dougfather

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Jul 11, 2006
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if your not using an ECM then all you need is the wires to the starter, battery, alternator and distributor

Don't forget the wiring to the AC Fan and Compressor too, if you are using them. I am doing the same swap as you are in im 84 Grand Prix...I assume Chevy 350???. I plan to delete the ECM. I was fortunate enough to buy a dealer service manual on eBay for the 84 GP/Bonneville. The ECM wiring is in with the AC/Heating wiring (passenger side). I plan to work on that soon, maybe tonight. That needs to be seperated.

The wiring on the driver's side bulkhead is pretty much essential. There are 2 halves to this connector. One includes headlights, wipers, turn signals, etc. The other is for the egine (dist, oil send, temp send, starter, alt send, 2 red wires to power up everthing else...etc). As for a schemtaic, there are several pages in my book on this. Some of the better Chilton's or Haynes manuals have the schematics.

The easy thing would be to get a wire harness for a G-Body (Monte or GP)with a Chevy 305 (again, I am assuming you are using a Chevy 350, not an Olds 350). Easier said than done, however, as I have seen so many hacked up in the junkyards that they were not worth getting.
 

GP403

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dougfather said:
The easy thing would be to get a wire harness for a G-Body (Monte or GP)with a Chevy 305 (again, I am assuming you are using a Chevy 350, not an Olds 350). Easier said than done, however, as I have seen so many hacked up in the junkyards that they were not worth getting.

Keep in mind too that if you're tossing the ECM, you could replace that with the harness from a '78-'80 A/G-Body, '81+ Diesel G Body (no ECM) or even a B-Body, they used the same firewall connector block, but might have slight diffs in the wiring at the connector.
 

dougfather

Master Mechanic
Jul 11, 2006
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Keep in mind too that if you're tossing the ECM, you could replace that with the harness from a '78-'80 A/G-Body, '81+ Diesel G Body (no ECM) or even a B-Body, they used the same firewall connector block, but might have slight diffs in the wiring at the connector

Are you referring to the pass or drivers side harness? How is the wiring for the A/C Blower and compressor wiring done on a 78-80 A/G body? Is it on the pass or drivers side? My 84 A/C Blower wiring is on tha pass side in with the ECM.
 

GP403

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dougfather said:
Are you referring to the pass or drivers side harness? How is the wiring for the A/C Blower and compressor wiring done on a 78-80 A/G body? Is it on the pass or drivers side? My 84 A/C Blower wiring is on tha pass side in with the ECM.

Is the AC/Blower stuff run with/into/through the ECM/harness? or just through the same holes in the firewall?

I'm *almost* positive the AC/blower *control* harness goes through the pass. side on the early G's. It should come off the fuse block inside and go up under the dash to the controls, behind the glovebox and then out the passenger side up in the corner around the blower motor. I believe there's a big fat pair(3? looking at some photos r.n.) coming off the driver's side harness that goes back to the AC and blower under the hood for power. Not 100% certain but I think that's how it is.
 

illregal82

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no ac its a 72 corvette motor i heard thats the original LT1 so i need starter, battery, alternator and distributor wires i heard they have the diagrams at the libary
 

illregal82

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so does anyone know the colors of the wires or how i figure what wires i need for the starter, battery, alternator and distributor i will not be using the ecm and only heat no a/c
 

dougfather

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Jul 11, 2006
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ok. I did some work on the 84 GP last night. Here's what I did:

-removed wheel well on pass. side. Note that there are 2 bolts between the well and heat box (I thought I had them all removed and started pulling with no luck).

- there are 2 wire harness's. One is for A/C and blower motor. The other, the bigger of the two, is for the ECM. Remove the 2 screws on the metal plate. Then, get inside the car and disconnect the 2 connectors on the ECM and the other connector that goes from the ECM to the dash. There's also a BARO sensor that needs to be removed. You can then pull out the harness from the outside. BE PATIENT!!! You shouldn't have to cut anything.

-now, for the wiring you need. The harness on the DRIVER'S side is the key. There are the following: (#AWG and color)

- #12 PURPLE goes to starter solenoid. This is from the ignition switch.
- #12 RED goes to starter (there are 2 of these wire and may already be spliced together with a ring terminal - these feed power to the rest of the car)
- #12 PINK goes to distributor.
- #18 BROWN goes to the alternator (term 1 that goes to the regulator)
- don't forget the alternator wire to the battery. This stands alone.
- there are others that go to the temp sensor and oil pressure sensor. I can get these as you need.
 

dougfather

Master Mechanic
Jul 11, 2006
286
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Altoona PA
oops, I forgot one more thing. There is a 3 pin connector with red, green and brown? (maybe black) wires that connects to the AC/Heat?Fan harness. Just plug into that harness.

As for oil gauge and electric choke, they are on the same circuit. If you keep the electric choke, but use and aftermarket oil gauge, you need to jumper the oil send plug as well, otherwise you don't get power to the electric choke (been there, done that on my old 81 Cutlass 4 dr). The factory oil send plug has 2 terminals with 3 wires, with 2 wires on the same terminal.
 
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