Bouncing Tach & won't start

[cobrasnake]

A buddy with a 2004 SPF, Roush 427R, MSD 6AL, MSD distributor and coil has the following problem (he does not drive the car much).

Turned on ignition switch (not motor) - tach bounces generally from 1-3+K in a wild dance.
Engine will crank but not turn over - plenty of battery and fuel - it will not even catch. It sounds like the wire from the coil to the distributor is not connected, but it is. Pulled distributor cap - contacts are worn and a little dirty. Scraped off debris - no change. Changing rotor and cap wouldn't hurt but it still should have started and does not explain bouncing tach.
Did not have a multimeter to test for voltage or resistance and to be honest, I don't know what to test.
We swapped the coil from my car to his, no change - still would not kick over.

Recommendations of what to test would be appreciated. I will bring my multimeter over next time.

Thanks - Tom

[CWizard]

Tom-
A few weeks ago my MSD 6AL failed, and one symptom before it quit completely, was a wildly bouncing tach. This MSD web page tells how to test the box. It's really simple, no meters needed: MSD Ignition

The test takes the distributor out of the circuit and should confirm that the MSD box and coil are ok or not. Elsewhere on the MSD site there are instructions for testing the resistance across the magnetic pickup in the distributor (assuming this is the kind of dist. your friend has). Good luck.
Jerry

[cobrasnake]

Jerry - great link - thanks - I will pass it on. Tom