Electronics Need help wiring something up? Thinking of adding an electrical component to your car? Need help troubleshooting that wiring glitch?

No relay or ecm power

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Old 04-23-2009, 11:37 AM
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No relay or ecm power

Hi Guys, I did an engine swap, an 85 v6 to a v8 carb. I used a donor harness from an 86 TPI engine. I can get the engine to run, ignition, starter, lights work, but I had to by pass the fuel pump wiring to get the engine to run.

My problem is, I don't have 12 volts at any of the relays or ECM. Not sure what I'm doing wrong. I do have a single orange wire that I can't figure out
where it goes. I've attached a pic. If you guys can tell me where this orange wire should go, it would be a great help and any/all suggestions as to where to look as to why I can't get power to relays and ECM would be greatly appreciated. I've checked and reseated every fuse I could find.

Thanks for your help, Walt
Attached Thumbnails No relay or ecm power-orange2.jpg  
Old 04-24-2009, 10:10 PM
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Car: 91Z28
Engine: 305
Transmission: WC T-5
Axle/Gears: 10 Bolt Posi, 3.08
Re: No relay or ecm power

Why are you concerned with the computer if you went carb? Your car does not need it. IS this a computer controlled Q-jet? If it is not you should be able to run your motor with just the basic wires.
Old 04-29-2009, 10:50 AM
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Re: No relay or ecm power

I'm ok with the computer, I know I'm not going to use it at this point, but shouldn't I still
have power going to the ecm and relays? I just want to be sure the harness I'm using is working properly.

I rewired the fuel pump to the ignition, but will my gas gage and other gages still work and be accurate? It just seems odd that I don't have power going to ecm and relays, even though I'm not going to be using the ECM. As far as I can tell, the harness is complete.

Thanks, Walt
Old 04-29-2009, 11:27 AM
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Car: 1985 Z28
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: garbage 2.73
Re: No relay or ecm power

**EDIT**

There is an orange wire with a 20amp inline fuse that routes all of the 12v power to the fuel pump relay, burnoff relay, MAF relay, fuel pump switch, AND ecm. Its hot at all times, so look if there is something on the battery that may not be connected, or another orange wire that is hot with 12v to connect. Worse come to worse, run a new line from the batt.



If you dont have 12v at the ECM, you have to ask yourself, where does this voltage come from? Trace your wires by hand if need be, and keep going back until you find the 12volts, then work forward and see where the disconnect is.

As far as your mystery connector, wheres that thing located?

Your gauges should still work. Temp gauge, oil pressure, and voltage gauge all come from their respective devices. Gas gauge comes from the tank, and it doesnt sound like you messed with that.

Finally, which relays?

Last edited by kcallais; 04-29-2009 at 11:34 AM. Reason: BRAINFART!
Old 04-29-2009, 09:16 PM
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Car: 91Z28
Engine: 305
Transmission: WC T-5
Axle/Gears: 10 Bolt Posi, 3.08
Re: No relay or ecm power

Also do you have a fuel pressure regulator before your carb? That fuel injection pump is going to drown your motor.

Did you swap the dash harness as well?
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