Need help with diagnosis

[zellerj]

Usually my engine starts within a second or two. This summer, it happened twice - I turned the key to start and there was nothing - no clicking and no sound what so ever. I put a screw driver across the two large terminals on the stater solenoid, and it starter spun but the starter did not engage the flywheel. Went back to the cockpit, and then the ignition switch worked to start the engine. This no start issue happened in June, and the key switch worked fine for 6 weeks, and today I had a no start issue again.

My experience with older engines is that jumping the solenoid causes the starter to engage with the flywheel. So I was surprised that the starter just spun without engaging with the flywheel.

Why would spinning the starter affect the key switch, so that after jumping the solenoid, the key switch started the engine?

Can someone make sense of this?

Best
Jim

[joe_db]

Usually my engine starts within a second or two. This summer, it happened twice - I turned the key to start and there was nothing - no clicking and no sound what so ever. I put a screw driver across the two large terminals on the stater solenoid, and it starter spun but the starter did not engage the flywheel. Went back to the cockpit, and then the ignition switch worked to start the engine. This no start issue happened in June, and the key switch worked fine for 6 weeks, and today I had a no start issue again.

My experience with older engines is that jumping the solenoid causes the starter to engage with the flywheel. So I was surprised that the starter just spun without engaging with the flywheel.

Why would spinning the starter affect the key switch, so that after jumping the solenoid, the key switch started the engine?

Can someone make sense of this?

Best
Jim

New or old style starter?
I had enough problems with starter buttons getting erratic that I made a solenoid-solenoid. My starter button operates a relay that operates the solenoid and I have never had a problem since.

[Al Schober]

Sounds like you have an electrical issue.
The late model A4 starters do not have a Bendix drive as such - the starter solenoid moves a lever that engages the gear to the flywheel.
Jumping the solenoid sends power to the starter and it spins, but it doesn't move the lever to engage the gear to the flywheel.
Time for some new switches/wiring and to make some choices. Do you want a key for off/on - why not just a toggle switch? If you want a key for off/on, do you want a 3rd position for 'start' - perhaps just a push button?

[alcodiesel]

I always left the key in the ignition switch. When the switch began to be unreliable I installed a toggle for the ignition and a pushbutton for the starter. Very happy with this config.