OK guys so bare with me. Not only am I trying to find a wire that's hot while cranking and in run, but I'm also trying to learn to read the wiring diagram to find my solution. There are a few threads where people,including myself, are asking for a hot while cranking wire, and yeah, the good ole pink w/black under the dash will work, but I'm trying to find a better solution.

A) So I'm wiring up the HolleyHP ECM, and I need a hot while cranking and run, to actually turn on the system.

B) Upon reading the attached diagram, it appears that the black/pink, and black/green wire in the top right, D15 and D16 are hot while cranking and run.

C) In the actual car, these wires are spiral wound together with a black, presumably ground, and they each go to a bank of injectors.

D) each of these are right there at the fender, not a foot away from the Holley wire that I need a hot/crank power source. Can I not simply connect to either the black/pink or black/green injector wire and be done???

Wiring diagrams are practically chinese to me, so any help is appreciated.
Thanks,
Chris

 

The more I think about it, the less of a good idea it seams. ....is there a hot while cranking wire coming IN to the computer??? I would think it'd have one similar to the Holley, but I dunno, maybe it doesn't.

 

Edit ..... I was wrong ! ( I had a brain fart ! )

I don't have 89 schematics, but I do have 88 schematics. The 3 fuses I see feeding RUN, BULB TEST or START voltage are the GAUGES, TURN B/U, & ENG CNT fuses. Again; not sure if the 89 is exactly the same as the 88.

Try the Pink/black wire at the ECM C1 connector, PIN A6. ( comes from the ENG CNT fuse, passes thru C207 @ PIN 'F' )

 

I have two considerations to mention here ;

First and most basic , how much power is the wire from the new ECM going to draw ? The fuse is 10 amps and an amount of those 10 available amps will already be being used by the injectors . Who knows maybe for a guess if we say the injectors draw 5 amps that circuit can only give you about 4 more for 9 amps total . When you approach 10 the fuse would melt over time and at over 10 it would open quicker . If this is only a "turn on signal" of milliamps draw you'll be fine but if it does draw something heavy minding the amps would be a good thing to do .

The second consideration is where the wire in question that your thinking of tapping off of feeds one bank of injectors , that means even the positive side of that circuit will be seen to pulsate somewhat if looked at on an Oscilloscope . This is because anytime your switching a coil (or a set of 4 of em in parallel like our bank of injectors here) the repeated rising and falling of the current as the injectors are commanded to spray and then the power is stopped to close them will put a choppy waveform on the line that the new ECM may find objectionable if the circuit in it is that sensitive of not getting 100% pure DC .

Just a couple of random thoughts I had when I read your post . I trust by now you did hook it up and it's been OK so far ?

 

I think the ECM trigger wire is a better idea too. I understand this to be needed as a 'trigger' signal,.. not the main power "IN" wiring for the Holly ECM.

The ENG/CNL fuse seems to be the best suited for this purpose. ( if it exists in the 89 !! ) For comparison: the GAUGES fuse feeds switched power to no less than 12 different things; it's a 10 AMP fuse with a 1mm wire. The ENG CTL fuse is also 10 AMP and the same gauge wire, but it only supplies a signal to 2 things,... the ECM and the ESC module.