If you have Centech harness & Howell TBI, I need help ID'ing 12v source! HELP

[Goldhawg]

I am installing the Howell TBI, and have a Centech harness. I'm at the end of the big upgrade (cam swap, TBI, & explorer serpentine). I need a 12v source that is off when key off, on when key is on and on when key is in the start mode. 2 months ago when I initially started this process I found a small black lead on the bottom of the ignition switch that meets this requirement (see pic). So I get everything hooked up and turn on the key, and for some strange reason the EFI system won't come on (no fuel pump, etc, even though I have 12v going into the Howell entry (see pic 2). When it splits off, the voltage drops to 1.6v for each of the three leads. When I applied a separate 12v to that end, the system kicks in and the fuel pump comes on (and can read 12v at each of the three connections). Thought it might be my male weatherpack connection, or the wire I used, so I pulled the ignition out and got a nice fat 12 gauge wire, and the exact same thing.

I don't know why, but this little black lead will not support the electrical pull. So I need another source that is Ov, 12V, and 12V in each of the three key positions. But now I have a new cam in and I can't be turning the engine over trying to test each line to find this source (and my memory from 2 months ago is only the small black line held 12V when engine was cranking on the ignition switch). I tried just disconnecting the starter lead to then be able to turn the key to crank w/o turning engine, but then nothing happens--circuit must need the starter hooked up to work.

Help!! Someone must know another source for this 12V power supply!

 

[a67and77]

If I remember correctly the white wire on the centech harness would be the crank run/coil positive. Anyone else have something?

 

[73bronco]

That appears to be the wire that runs your brake warning bulb! I just discovered that when I was looking for the same type of wire for my EFI swap. I ended up using the signal wire for the alternator(green with white stripe on my stock wiring). Works great now!

 

[Goldhawg]

That appears to be the wire that runs your brake warning bulb! I just discovered that when I was looking for the same type of wire for my EFI swap. I ended up using the signal wire for the alternator(green with white stripe on my stock wiring). Works great now!

Hmmm...maybe that's why my brake lite is on when I turn the key on!

Ok, did you just run a longer lead from in the engine bay back into the cab? I was hoping for a wire in the cab to draw from, but I'll take whatever will work....

 

[RRRAAAYYY2]

Toggle switch in your cigarette lighter spot might make for a cheap anti theft deterrent.

 

[DirtDonk]

Does this connection need to be under the dash? If under the hood is ok too, what starter relay/mag switch (since Ray is reading this ;D) are you using? If original type, or similar that has an "I" location, you could pull a wire from there to get your hot-in-start signal.
If you're still running a stock-type ignition though, and using the White jumper wire in the Centech harness to super-juice the coil while in start, it might not work for you. Don't know what having a signal there all the time would do to your computer. Might make it think that the starter is always engaged and mess things up.
Check with Howell on that score, but at least it's an alternate source for power in START.

Side note. If you're running the Centech and don't have any ballast resistor to the coil circuit, you don't need that additional wire to the "I" terminal of the starter relay anyway. So you can use it as a dedicated terminal post for your Howell's hot-in-start circuit. And even have plenty of extra wire from the Centech harness if you need to pillage some from somewhere.

You might even check your ignition switch too (since it looks like you have it out) and make sure that you don't in fact have a terminal that's hot in both Run AND Start.
Haven't checked the one in Centech's kit myself, but some of us have found that the stock Bronco ignition switches do in fact have one terminal that has power in both positions.
Worth a quick check anyway.

Paul

 

[RRRAAAYYY2]

Should there not be one terminal for the ignition that is live both in run/start. I thought (big I thought) that the solenoid "I" terminal was only feeding extra juice to the coil during the crank cycle. But I could be way wrong on that.

I still think a seperate switch is a good idea, help deter theft. Just my opinion though.

 

[Goldhawg]

You might even check your ignition switch too (since it looks like you have it out) and make sure that you don't in fact have a terminal that's hot in both Run AND Start.
Haven't checked the one in Centech's kit myself, but some of us have found that the stock Bronco ignition switches do in fact have one terminal that has power in both positions.
Worth a quick check anyway.

Paul

My problem is I now don't want to check for power sources w/key in crank mode, since the engine will turn over. I have a brand new cam in that I don't want to rub any of the lube off until I actually start it and do the elevated RPM 20 minute cam break in procedure. I am hoping there is someone out there that has both the Centech and Howell and can definitively tell me a source that I can use for this rqmt.....

Re your other comments, I'm not much of a wiring guy (which is why I was happy when the bronco already came w/new Centech harness when I bought it), so I'm not sure I understand all the good stuff you're trying to tell me, but thx!

 

[Explorer]

Check on the passenger side loom when it comes out of the firewall. There is a green double wire with a single connector marked "aux". See if that will fit the bill for you. Disconnect the starter wire and you can check for power in crank position without turning engine over.

 

[DirtDonk]

Ditto what Explorer said. Either disconnect the starter and check with a light, or, what I was thinking when I mentioned to check the switch was to have the battery disconnected altogether and check with an ohm-meter at the switch.
Either way works, but if you're not that up on electricity and it's many foul tendencies, maybe you don't have a volt-ohm meter? If you do, you can try either method.
If you're not sure, just ask and we can walk you through it.

As he mentioned also, Centech provides at least four wires that are "key on" and at least two that are "hot in start only" under the hood. PO might have removed any that weren't used, or they may be used or buried under there somewhere.
You'll have to check to see if they're hot in both positions though, since I can't test mine just yet.
If you haven't got it in the next couple of days though, I should be able to have a better answer then.

Good luck. And keep smilin'!

Paul

 

[DirtDonk]

Should there not be one terminal for the ignition that is live both in run/start. I thought (big I thought) that the solenoid "I" terminal was only feeding extra juice to the coil during the crank cycle. But I could be way wrong on that.

Yes, if he still has the original Bronco starter relay. If it's a more modern one from a late-model EFI vehicle, it won't have that terminal.
"Separate ("but equal") would be good.

Paul

 

[ransil]

Does the EFI system have 2 wires or 1 wire??

If it only has one wire you can get Dual relay or wire up 2 relays in parallel.
both outputs pin 87 will go to the EFI, the control pins 85 will be fed from IGN run and Start

Cepek used to make a dual relay, way too big for your needs. here is a diagram and pic.
http://street2mud.com/forum/index.php?showtopic=12&mode=threaded