DME Interchangability

[simssj]

I'm at my wit's end with my no-cold-start problem with my 1987 924-S (NA). I've checked everything under the sun and the only thing I haven't been able to verify is the DME itself.
- Fuel Pressure: Check!
- Spark: Check!
- Compression: Check!
- Tach Bounce / Reference Sensors: Check!

I'm looking for a substitute DME as the last resort, and I note (Thanks, ECUDoctors.com!) that there are three distinct part numbers for the DME for this year: 0261200058, 0261200077 and 0261200086.

The one that's in there is 0261200077 but the PO had made an obscure note in some of the paperwork that he gave me; something about changing the DME a dozen or so years ago. My questions are:
1) How can I determine the "right" part number for my year / model? (US-car, 5-speed) (In other words, is mine the *right* one?)
2) Are the DME part numbers generally interchangable, if I happen to find a good deal on eBay / CraigsList / what-have-you?

I'm bargain-shopping at this point, since I've been told my job is being eliminated at the end of the month, and with all the Christmas expenses, and what-not. But I would appreciate a little insight from the collective brain-trust before I bargain-shop myself into a dead-end.

Thanks!

[John_AZ]

Your '87 924S has the OEM 944 618 121 04
Porsche 944 - 1985.5/87 ROW

If you dig further you will find the correct OEM chip installed in the DME on the same site.

Earlier DMEs will work but not have the improvements the 944 ...04 used.

J_AZ

[simssj]

Thanks, John!

I took the plunge last evening and yanked the DME out and opened her up.

It was obvious and apparent that someone had been in there before; there are numerous patches of dried flux and a couple of *very* sketchy solder joints.

I'm planning to give the board a deep cleaning and re-flow as many of the solder pads as I can get to.

Maybe there's life in this one yet. Maybe not. But nothing ventured, nothing gained, I suppose!