Key on starter voltage drop

[71340RT]

I'm running the Holley terminator x max computer for my Gen 3 Hemi swap on my 73 Challenger and have a problem with where to get the least amount of voltage drop for my key on switched power to the terminator x max computer. When I crank the engine over on 2 different wires I have hooked to both drop to below 2 volts which is not enough for the Holley computer. Manual reads it should be hooked to a clean 12 volt power source active with the key on. This seems to be a problem only with Holley computers needing more voltage. Thanks for the help.

[dodj]

If the key switch isn't good enough for it, how about using the key on to energize a high quality relay and transfer 12vdc right from the battery?

[Barracuda1]

I agree with dodj.  A relay will be the best way to accomplish this.

Mike

[71340RT]

If the key switch isn't good enough for it, how about using the key on to energize a high quality relay and transfer 12vdc right from the battery?

I had thought about this so maybe I will give it a shot. I can't believe all the key on power source's drop voltage that much so this maybe my next thing to try to see if it will let the engine fire up.

[bdschnei]

I don't know about the Terminator, but the instructions for the Holley HP and Dominator computers is pretty clear that both the 12v and primary ground for the computer must come directly from the battery in order to minimize voltage drop and keep the power as "clean" as possible. The computer is actually switched on via a separate 12V signal which only provides the "on" signal to the computer, as the primary power is provided by the aforementioned 12v directly from the battery. Guessing the Terminator wiring is similar.

[dodj]

I can't believe all the key on power source's drop voltage that much

Well, ebody connectors are famous for developing poor continuity. You can loose voltage at the switch, column connector, and bulkhead connector. If you haven't already, clean those terminals and maybe find a reason for your voltage issue?

[71340RT]

I don't know about the Terminator, but the instructions for the Holley HP and Dominator computers is pretty clear that both the 12v and primary ground for the computer must come directly from the battery in order to minimize voltage drop and keep the power as "clean" as possible. The computer is actually switched on via a separate 12V signal which only provides the "on" signal to the computer, as the primary power is provided by the aforementioned 12v directly from the battery. Guessing the Terminator wiring is similar.

You are right about the primary power and ground they must come from the battery directly. The problem seems to be my 12 volt keyed switched signal having to much voltage drop and will not let the computer operate. I have talked to Holley and they said I need a clean 12 volt keyed source and check with volt meter. They all seem to have to much voltage drop which Holley says is the problem as one of the wires only had 2.9 volts during cranking.

[71340RT]

I can't believe all the key on power source's drop voltage that much

Well, ebody connectors are famous for developing poor continuity. You can loose voltage at the switch, column connector, and bulkhead connector. If you haven't already, clean those terminals and maybe find a reason for your voltage issue?

Thanks I may look at it again but I could not locate the problem. I will check some of the terminals at the bulkhead and check the column connector.

[dodj]

2.9v?!?
Previously, when you said under 2v, I thought that was a typo and you meant to type 12.... if you are dropping that much makes me think battery or starter cables.
A faulty battery will drop in voltage big time when under load. A faulty battery cable will cause a voltage drop to the starter causing even higher current demands which will cause the battery voltage to drop. Try another battery or parallel two batteries with jumper cables.

[chargerdon]

My bet is still on the start circuit wiring.   I had a similar problem on my 74 challenger with electronic ignition.   The car periodically would not start with the key, but if i turned it to "run" and then jumpered the starter relay to turn it over it would start every time.   Recognize there are two different paths for the current...Run is one, and start is different.   You might try the same thing...i.e. if you turn the key to run instead of start what is the voltage where you were getting the 2.6 ???   

Start at the obvious places...first is the flat connector at the steering column...trace the wires and find the one that is for the "start" and test the voltage there when trying to start...both sides of it.   if that is good, then next it goes to the bulkhead connector...   These often get dirty or rusted...   with a probe test the current when starting at the engine side of the bulkhead connector...   Use the wiring diagrams to see which connector it is.    On my challenger that was were the problem was...and to correct was a horrible experience...i had to remove the connector and clean it first on the engine side...those spade connectors are difficult to clean well...   Next the female side which is the wire that goes into it from under the dash...   Another that is difficult to clean....   Get that connection clean and ill bet the problem gets cured...   

[71340RT]

Thanks for all the comments. I will start checking and see what I find so I can get the Hemi swap running it has already been 8 months longer than I figured because of back ordered parts. I also got spinal stenosis of my lower back and neck which has slowed me down and is not fixed. I got this right after I was under the car putting the exhaust on and running the fuel lines. Not sure if this caused it but I do a lot less now than I ever did. Thanks and hope I find the issue.

[Katfish]

Is your controller under dash, or out in engine compartment?

[71340RT]

Is your controller under dash, or out in engine compartment?

It is under the dash as I had problems with my Edelbrock EFI ECU had problems under the hood.

[71340RT]

I ended up adding the relay to run power from the battery. I ran my ignition on wire from the ballast resistor hooking the brown and blue wire together and running one wire to the relay. This ended up with little voltage drop and the 392 Hemi fired right up. Thanks for all the input on this problem.