308QV Ignition Switch

What year/version 308QV?

I'd confirm/deny +12V on the start command line with a voltmeter before resorting to taking the ignition switch apart. You don't need to go to the starter to do this -- it can be measured by removing the approriate relay and measuring for voltage presence/absence at the appropriate female socket (but confirm year and version if you'd like something more specific).

 

The relay names aren't revealing, but the line from the ignition switch terminal 50 (start command) is used on two relays. From the schematic in the '84-'85 US 308QV OM 307/84:

Two "B" (white) wires leave terminal 50 on the ignition switch -- one goes to the starter solenoid; the other goes to:

1. terminal 86 on relay 83 (aka relay F - relay for brakes warning light) -- this terminal should be +12V relative to ground during starter motor cranking. Sometimes they inadvertantly swap the labels for terminals 85 & 86 on the schematic so also measure the voltage between terminal 85 in the relay socket and ground. If either 86-to-ground or 85-to-ground is +12V during starter motor cranking, your ignition switch is probably OK (and you'd then need to check the voltage on the B wire at the starter solenoid).

2. terminal 87 on relay 90 (aka relay G - relay for start injector) -- this terminal should also be +12V relative to ground during starter motor cranking (if fuse 130 is still intact).

Try either/both of those first -- you don't want to mess with the ignition switch IMO unless absolutely necessary

 

My 85QV did the same thing.... It was a faulty conection in the fuse box..... A new rivet in the connector was a quick fix...Birdmans fuse box installed cured the problem for good.

 

Not really, but when you make the measurement on relay F you could just stick one probe in the 85 socket and one probe in the 86 socket (even if they are mislabeled, one should be +12V when the key is in the start position and the other will be ground). Also (with everything plugged in), if your brake failure warning light goes "on" when the key is in the start position (as it should for its self-test), that's another sign that your ignition switch is OK (and conversely, if it doesn't, that would be a bad sign for the ignition switch).

With regard to "Birdman's fusebox" just do a search -- but this isn't involved in your problem IMO -- none of the start command wiring goes thru the fuseboxes. If your symptom was "starter cranks the engine over OK, but engine never fires" then I'd suspect the fusebox since both ignition and injection power go thru the fuseboxes.