Ref Sensor ?
 

I put my car back together and have been driving for several months trouble free.

This past week it is died a few times. Usually won't start for a while (more than half an hour) afterwards.

Today it died three times and I was finally able to get home. It is like you just turn the ignition off. I noticed when I was cranking it that the tach was not wobbling. Is there anything other than the ref sensors that would cause the tach not to wobble?

Had it die once right after I got it back together but that was the fuel pump relay.

Hope that makes sense.

So I checked the sensors and the reading are right on.

Sounds like the DME solder is next ?

If the sensors check out with the Clarks resistance check, did you regap the sensors?
Speed and Reference Sensors - Checking, Replacement, and Adjustment


Did you replace the DME/fuel pump relay?
DME Relay Information and Testing

Check the sensor connection at the top of the engine in the rear. You may have already done this when you checked the sensors.

The next step is to check the bell housing ground negative cable. Put a piece of tape over the TDC hole so nothing drops in.
Next to the big bell housing ground is a small ground. Clean this ground too.

Clean the connection at the rear of the DME computer box under the dash.
http://www.clarks-garage.com/shop-manual/dme-05.htm

Solder the DME..............yes, I would do it before I searched for a DME replacement.

DME Repaired w/pics - Rennlist Discussion Forums

or
Early DME repair write-up with pics. - Rennlist Discussion Forums

GL
John

Thanks John,

I don't see any obviously bad soldering but am resoldering this afternoon anyway.

I'll clean all the grounds again and the wires to the harness from the + battery terminal could use a little work, too.

I didn't pick up a back up fuel pump relay. I need to do that anyway!

Thanks

Check and clean wires on positive battery terminal bolt (small wires) one wire sends power to dme relay on fuse box look for basics first (kiss theory) regards tom

Speed and reference sensors in these cars can create a great many maddening and hard-to-figure-out problems. Replacing them every so often is cheap insurance against headaches. I'd recommend every other belt change or so.

So I did everything except adjust the ref sensor clearance. I'll do that tonight.

I didn't hit all the solder connections on the DME. Just the ones where the wires connect the boards. Didn't see any cracks in any of them. The only ones that didn' t look perfect were the ones I resoldered. They only looked a little funny because of the flux that was left.

Am I correct in that if I stop getting a signal from the ref sensors it has to be the sensor itself, the sensor spacing, the sensor wires or connectors or the DME? Could it even come from a bad ground? I'm pretty sure I cleaned them all when I put this back together last fall.

Porsche-O-Phile, that sounds like a plan. Eliminates one more source of mystery with a 30 year old machine.