usafws6

iTrader: (10)

like the title says i need to find a circuit that is hot in run and crank. every circuit ive tested is either always hot or hot in run only. i had both wires hooked up to a switch on the dash to get the car running but now its time to clean all the wiring up so i need help with this. car is 72 nova with an ls1 swap ebay harness and a painless chassis harness. the red and pink wire that provide power to the ecm require the red to be always hot for pcm memory i guess and the pink needs to be hot in run and crank to provide power to the injection system. any help is greatly appreciated.

bronx_peanut

What I used was the key on power that went to the HEI distributor coil. If your car has points try the wire that runs to the points it should be hot during cranking and key on.

usafws6

iTrader: (10)

the car didnt have a motor when i got it. i cant find an hei wire either. i guess ill just use a switch if i cant figure it out.

flame

iTrader: (13)

Go right to the ignition switch to find a wire and use a relay so you don't overload the old switch

bczee

iTrader: (12)

72's didn't have HEI's. Question, Why would you need the pink wire hot on both run and CRANK ? I've only wired my ECM / Pink hot while Ign is on Run..

Most of the older 60's and 70's Chevy's.. used a second wire to the points that came from the starter solenoid, This was to give full 12 volts to the point/coil.. as the coil/points were connected to a resistor block to reduce the 12 volts to a lower voltage. (some had it, some didn't use it)

As stated, a fused Relay circuit should be used to power the Injectors, coils, etc. You can use the wire that goes to the Coil/points or if it has a resistor block, use that wire to activate the Relays.

You should also find a Ign/Run Hot off of the 72' Fuse box. Also suggest running a fused relay system from it.

BC

psiconversion

iTrader: (5)

I'm assuming your EBAY harness is looking for a key ON/CRANK source? To power the EBAY harness's fuse block?

On the factory Nova chassis harness there would have been an 'IGN' port in the fuse block which would provide power in Key 'ON' and 'CRANK'. The 'ACC' ports lose power when you are cranking. The painless harness should have the same. As stated above, HEI was not available until around 1976, so your factory ignition wire (white braided) would not be 12 volts as it is a resistor wire. I would look for the purple or pink wire at the base of the column (test for 12 volts in key on and crank) if you cant find something in the painless chassis harness.

Jon
PSI

flame

iTrader: (13)

If it isn't hot in crank then your coils will not spark during cranking and the engine will not start

lizeec

iTrader: (57)

I did as PSI suggested, 1974 was the transitional year for HEI some cars had them and some didnt if you had HEI that ignition wire is the one you want to use, if you had points it was the cloth covered resistor wire, my car had the cloth one I traced it back to the fuse box and removed the terminal at the fuse box and removed the cloth wire and soldered in a 12 gauge wire at that terminal and that is my 12V ignition wire that is hot in the run/crank position.

usafws6

iTrader: (10)

exactly, its easy to find hot in run, but run and crank not so much. ill look for the coil wire. i like the relay idea if but i need a schematic.

bczee

iTrader: (12)

I also did what lizeec did.. I re-did my OEM Fuse box and ran a new 12+ Hot circuit wire to the Fuse box from the Battery due to the increase Amp's that I expected to be pulling.

I also added a Painless 7 circuit fuse box and ran a few new wires to feed the PCM and other circuits out of it.

I had no trouble with voltage dropping after the Ign switch was moved from Crank to Run.

BC

flame

iTrader: (13)

See attachment

usafws6

iTrader: (10)

87, 86, and 30 are obvious, but were does 85 come from? im guessing a wire from the ign switch on the column, but the pink one is constant and the car wont shut off with it wired to that one.

flame

iTrader: (13)

85 is the wire from the ignition switch that is live in crank and run

usafws6

iTrader: (10)

thats what i thought, ill have to check again because i couldnt find one that wasnt constant or didnt drop voltage in crank.

usafws6

iTrader: (10)

i just checked again there isnt a wire that is hot in only run/crank. my only option is a switch i suppose.

LS1MCSS

iTrader: (18)

If you have a pink wire that is constant 12v, then you may have other problems. Pink wires should always be switched 12v and orange wires should be constant 12v.

usafws6

iTrader: (10)

Ill have to check that

flame

iTrader: (13)

Maybe try asking someone that has done a 72 Nova before. I looked at the wiring and I think you are right that there is no wire on the switch that is live in crank/run. It appears your coil was power from the starter solenoid.

usafws6

iTrader: (10)

Thats what i was reading, but the ls1 starter doesnt have anotherterminal for that

flame

iTrader: (13)

maybe try a newer year ignition switch as long as the mounting is the same