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EFI Wiring question. Older Painless/RJM harnesses

Z Bronco

Bronco Guru
Joined
Mar 17, 2007
Messages
1,138
I have the Painless Bronco/scout/fj40 harness and am installing the RJM EFI harness. In connecting the RJM Ignition Run Orange wire to the Ignition Run of the Painless harness, can I connect to the coil+ of the Painless harness since the coil wires are no longer used because of the EFI harness wiring and different coil? Or, do I run a wire to the old 904 wire spot on the ignition switch? Wanting to wire it correctly, but unsure, don't want to mess up the wiring as I am in a stupor from days of shoveling snow from the recent winter storms in Central Oregon.

Thanks in advance,
Z Bronco
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,345
Either should work I would think. As long as it's got 12v to the wire with the key in RUN, then it should work for your purposes and you don't need to run a dedicated wire to the key. You already have that with the new harness.

Basically, your RJM harness needs 12v all the time, 12v with the key in RUN, and 12v with the key in START modes. They don't really care where the source comes from, as long as it's clean and not from something like the alternator output or somewhere that "noise" might be excessive.
And speaking of which... Make sure you have a good charging system, battery and, most especially, additional ground circuits from the battery, engine and body. More than Ford put on EB's to begin with.
Your computer will thank you for the additional effort.

Paul
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,345
Another wire that's often used as a source for switched 12v is the old voltage regulator wire.
Are you still going to be using an externally regulated alternator, such as a stock one? Or are you upgrading to a more powerful and internally regulated alternator?

Paul
 
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Z Bronco

Z Bronco

Bronco Guru
Joined
Mar 17, 2007
Messages
1,138
Thanks Paul. Here is some more information.....

I will be using the explorer serpentine setup which I believe is a 4G alternator, so internally regulated (had a one wire 3G before). The coil+ wire (#720 14 gauge, pink wire, from the Painless supplement for the 10107 wiring harness) originates from the Fuse panel. The voltmeter gauge (#735 18 gauge) also originates from the Fuse panel. I have Autometer gauges in my homemade dash and there is a Volt gauge in the dash, so I think that is hooked up, but I will check. I added many grounds when I rewired the Bronco years ago, and the battery will be new once I go pick it up (had an old Optima yellow top). Hope this helps.
 
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