I just wired up my Mallory 685 box. Car cranked up fine, I tested the rev limiter at 3000, no problems. Cut the car off, did some unrelated work. Came back, tried to start the car, and it won't crank. The box has power, it just won't crank up. I figured maybe the box is messed up, so I put the ignition plugs back to the stock and bypass the mallory box. Still won't start. I checked the Ignition fuse in the fuse box, its fine. That's the only fuse I know of that could blow and not let the car crank. All fuses are good too. Any ideas?

 

Just to clarify, you are using the work crank for rotating by the starter is that correct?

If your starter will not rotate the engine, check the voltage across the battery before you crank it and during cranking(with help). The voltage should not drop below 11 volts. Measure the voltage from the +terminal to the engine. If the grounds are good, should read the same as at the battery. Check the I/P fuse panel for fuse #16 to see if it's blown. Try jumping voltage directly from the battery to the starter to see if it will engage. If so, check the clutch start switch and don't forget the VATS will disable the cranking circuit through the theft deterrent module and the theft deterrent relay. Usually the security light will light or blink though. If you still can't find the problem, jump around the TDR from the yellow to the purple wire temporarily and try to crank it then. This will eliminate the clutch switch and theft crap to test the rest of the circuit. BE CAREFUL if you do, the engine will rotate with the clutch out.

 

Thanks for the suggestions. The car turns over, just never actually cranks up. Checked the interior fuse panel and no fuses are blown. Don't have a clutch start swith since I never wired it up from the A4/M6 swap years ago. VATS is disabled in ECU. What is the TDR?

 

for the hell of it pull of a spark plug wire and see if your getting spark