explorer swap with a existing centech harness

[Keitht1216]

anybody know what terminal on the ingnition switch is hot in run and start?
my centech harness is about 7-8 years old.

I have swapped a 97 explorer 5.0w/4r70w into my 72 with the help from EFIguy. i have everything hooked up, it cranks but doesn't start. my problem is that I`m doing this myself and I cant check the ignition switch to find a terminal that is hot in run and start. (holding the ohm meter probes on the terminals and turn the key to start. I only have 2 hands)

I called centech and they said the white wire marked "ign" on the back of the fuse block. but the motor just cranks it doesn`t even try to start.

i`m not 100% sure if this is my problem but its the one part of the wiring i`m not sure about.

any help would be greatly apprieciated

 

[lagbolt]

Are you getting fuel pressure?


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[Keitht1216]

I have fuel pressure at my fuel rail. pushed the Schrader valve on the fuel rail and gas squirted out. plus I can hear the fuel pump run when I turn the ign switch to run

 

[DirtDonk]

Assuming you're using the stock Bronco type switch and not the Centech supplied "universal" switch?

When the factory ignition switch is working "properly" the only terminal there is the Green one. I forget what number or location they apply to that in their instructions, but it's the only one with a Green wire.
The Purple wire is hot in START only.
The threaded center post is hot in ACC and RUN, but pretty sure not in START.

What that means is that, under the hood, most of the Green wires available will work for you. There should even be two unused ones over by the passenger side firewall. They're combined into one white connector and can be individually cut loose and re-terminated as needed.

If your switch is not functioning properly however, all bets are off. They do wear out after all, and unless yours was new at the time of the install, or bought directly from Ford or sourced from a junkyard, it definitely won't last forever.

Not sure how to tell you to test it with only two hands, but it can be done.

Good luck!

Paul

 

[Keitht1216]

I got it running. the white "ign" wire on the back of the fuse panel is hot in run and start. I did have something happen that I cant explain. I put a battery charger on my battery because it was cranking a little slow and I thought the battery was weak. with the charger on the battery I could not get the motor to start and the starter would get hot after cranking for about 10 seconds. so I let the charger on overnight. the next day once I figured out my hot in run/start wire. tried to start it with the charger still on it. with the same results starter turned kind of slow and got hot quick. I decided to take the charger off of it because it was showing a full charge. the next time I tried to start it the starter spun faster and it started right up. so somehow the charger was preventing the motor from starting.

 

[DirtDonk]

That is kind of strange, but not out of the realm of possibility either. Your charger, unless it's one of those big daddy START-type chargers, is only good for maybe 10 amps. Your starter is wanting to pull anywhere from 60 all the way up to 150 amps or so. Way more than your charger can handle on it's own.
Even the typical "start" position of some small chargers is only good for a short burst of 50 amps. A helping hand then, but barely enough to hold it's own if there is extended cranking.

Not sure why simply leaving it connected could change the dynamics enough to make the starter spin slow, but that and the extra heat are indicative of not enough capacity in the circuit. Just as if the cables were undersized or loosely connected or corroded.
Resistance is heat.

But hey, congrats on a success! Sounds like you got it no matter what. So with any luck you won't have to experiment with starting and battery chargers anymore!

Paul