1973 Mach 1 Electrical/startup Help


New Member
Sep 2, 2017
I'm new to this forum and was hoping you guys could help steer this build in the right direction for me. I'm pretty much a novice at this stuff

So ive got a 1973 Mach 1 with a 351c and an MSD 6al ignition box, pro-billet distributor and blaster 2 coil. I inherited the car from my dad and have been trying to get it running for over a year now. due to some wiring complications the old harness had to be taken out and replaced.

ive been working on this rewire for quite some time and finished this past week. before I tried to turn it over I checked to make sure I had spark, fuel and good compression. after that was all confirmed we tried to turn it over with a bit of starter fluid and it cranked but didnt fire. We made sure all the grounds were solid and checked the other connections.

Where i was previously getting a constant 12v to the "S" terminal on the starter relay with the key in the ON position, but I'm not getting anything now. Also, with the MSD ignition box there aren't any connectors going to the "I" post on the relay because the ignition wire is now spliced to the small red on the msd box. I also noticed that I'm only getting power to 2 of the fuses on the block, where I used to get 12v on all of them. Oddly enough the car still cranks.

Any help would be greatly appreciated. I wont be able to get under the hood again until Wednesday but i was hoping you guys could help me troubleshoot it until then.


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15 Year Member
Dec 3, 2002
Seattle area, WA
You say there were problems with the original harness and it was replaced. What was it replaced with?

Make sure your MSD box turns on with key on and stays on in crank. Also check the voltage at your coil both in key on and crank positions to make sure you are getting juice when and where you need it.