Hot start question

[bobe]

My 84 starts great cold but once hot, it won't restart till it cools. The tach does not
jump while cranking. Once it cools off I can see the tach jumping and I know it will fire up. I replaced the fuel dme relay and checked everything else as the manuals recommend. Is it a fair bet it's the reference sensor(s). Are the reference sensors independent of any other system if the car cranks over well.

Thanks

[jmd_forest]

The reference sensors feed the DME. There's a power transistor (mounted on a heat sink) in the DME subject to solder joint failure. Since you already replaced the DME relay you might want to pull the DME and inspect the power transistor for cracked solder joints. There's a good writeup on the rennlist forum. You could also check the connection of the reference sensors to the main wiring harness

jmd_forest

[bobe]

Actually I swapped the DME with a known good one and the car started right up.
It's just the hot starts now and no Tach movement that are the issue.

Thanks

[Outback Porsche]

This sound very familiar to me. Have you read my post;

Another 'Intermittent Start' Problem

Jeff

[bobe]

Keep me posted how you come along , I'll do the same.
Thanks

[Outback Porsche]

Sure.

The last thing I did was clean up all the ground points in the engine bay (incl engine, and terminals on alternator, battery, etc). Now going to drop the relay/fuse panel under the dash and clean, along with the ground point behind it.

Jeff.