Car has been off the road for a while. jst got motor back from Jorge at European Motorworks in Hawthorne. freshly rebuilt. while motor was out, I rewired dash to eliminate some of the race car stuff like push button start with no keys. SO i have reinstalled stock steering column and ignition switch.
with motor back in, I have 12 volts to the starter verified by multimeter. but when I turn key, nothing happens. multimeter shows just 3 volts to the solenoid terminal connection from the yellow wire, and only momentarily when key is turned, not constant even if key is held there.
in rewiring the ignition, I may have missed something but, whoever installed the start button just hacked off the wires so it was pretty easy to just reconnect color to like color.
One possibility is seat belt interrupt. I know 74 had that, but this is an early 73. I believe it only has seat belt warning light. but, with the light not being installed, and the set belt switches not in place, would that interrupt the starter circuit? I can only follow wiring diagrams so far, flow diagrams are a mystery to me.
there is a yellow wire and two grounds at the rear of tunnel that were probably the seat belt warning light system. Does anyone know, if these interrupt starter circuit?
Full Version: re-wiring former race car
Transaxle ground strap in place?
QUOTE(bkrantz @ Apr 30 2023, 05:59 PM) 
Transaxle ground strap in place?
Yes, that was first thing I checked, and even though I had reminded myself ten times, I had indeed forgotten it. but no change.
Sounds like you have a big voltage drop occurring somewhere in wiring to only have 3v at solenoid.
Schematic is your friend but here is the general route of the yellow wire
Ignition switch to seat belt relay interlock (maybe gone on a race car) to relay board in on pin 1 from cabin - out on pin 6) to starter.
You’re just going to have to ohm it out and trace the wire - god only knows what was done with race car wiring
Click to view attachment
Schematic is your friend but here is the general route of the yellow wire
Ignition switch to seat belt relay interlock (maybe gone on a race car) to relay board in on pin 1 from cabin - out on pin 6) to starter.
You’re just going to have to ohm it out and trace the wire - god only knows what was done with race car wiring
Click to view attachment
I would suspect the ignition switch, but the relay panel in the engine compartment and the harness connections to it could also be faulty.
Verify 12v on that large yellow wire either in the cabin or before it goes to the relay board. I agree with the switch theory. BTW, your batteries in your VOM are good, aren't they? 
QUOTE(Superhawk996 @ Apr 30 2023, 06:18 PM)
Sounds like you have a big voltage drop occurring somewhere in wiring to only have 3v at solenoid.
Schematic is your friend but here is the general route of the yellow wire
Ignition switch to seat belt relay interlock (maybe gone on a race car) to relay board in on pin 1 from cabin - out on pin 6) to starter.
You’re just going to have to ohm it out and trace the wire - god only knows what was done with race car wiring
Click to view attachment
thats some good info, thanks!
yellow wire from ignition switch.
Go up under dash, at the front of the tunnel.
Find the wire.
Use a sewing need for this.
Jam the needle into the center of the wire.
Does the wire have 12vdc at start position when you test the sewing needle to ground with a volt meter?
If yes...
Go to rear of tunnel, see if the yellow wire comes out of the tunnel and goes under the passenger seat into the logic circuit (looks like a relay, but its not)
Same test, with needle.
If it goes into and out of that box that looks like a relay....remove both ends and redo them to make them directly connected and no longer go through that box. There are many pics here...but its two solid crimp connectors, hard wiring that yellow wire.
Check the voltage at the starter again in the start position.
Go up under dash, at the front of the tunnel.
Find the wire.
Use a sewing need for this.
Jam the needle into the center of the wire.
Does the wire have 12vdc at start position when you test the sewing needle to ground with a volt meter?
If yes...
Go to rear of tunnel, see if the yellow wire comes out of the tunnel and goes under the passenger seat into the logic circuit (looks like a relay, but its not)
Same test, with needle.
If it goes into and out of that box that looks like a relay....remove both ends and redo them to make them directly connected and no longer go through that box. There are many pics here...but its two solid crimp connectors, hard wiring that yellow wire.
Check the voltage at the starter again in the start position.
FYI, I was able to track this down. Yellow wire IN TO the relay board, had a bad connection. starter is working now. but, on first fire up, the new motor made a horrendous noise. Turns out my almost new Bursch SS twin pipes had a loose baffle/. now waiting for that to be repaired.
QUOTE(RFoulds @ May 8 2023, 05:52 PM)
FYI, I was able to track this down. Yellow wire IN TO the relay board, had a bad connection. starter is working now. but, on first fire up, the new motor made a horrendous noise. Turns out my almost new Bursch SS twin pipes had a loose baffle/. now waiting for that to be repaired.
Keep after it. Only 98 surprises to go.
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