DME relay the problem?
 

Hello Pelicans -

88 Carrera, just returning from about a 100 mile round trip, coming off interstate ramp and engine dies. Everything powered, engines turns freely but not starting. After approx 5-10 minutes and some fiddling with the relay harness it cranks and runs fine... Is this the relay? Have had similar issue when first purchased car two plus years ago, the relay was replaced and fine til now.... does this sound like the likely culprit again?

Thanks

yaz

most likely. Only way to find out is to replace the relay.

Just to play "Devil's Advocate", it could also be an intermittant issue with any number of culprits. Hopefully, it's just the DME relay.

Dme.
 

If you can, swap out the relay with another P-CAR owner.

If it's the relay, replace with the factory unit, not the URO.

Ask me how I know.......

Good luck,

Gerry

I also had an issue with the supplied power from the fuse box TO the DME box. I habitually spin the fuses due to living near the beach. I wore down the contact points on the end of one fuse....intermittent short and it killed the power.

Replaced all the fuses.....some of them musta been 30+ years old...

Yes, an assortment of fuses and a spare DME relay or two are a must have on board.

I also carry a spare oil pressure switch.

Thanks! To all! I do have a whole packet of new fuses and I will give the ones in a spin while investigating the DME fuse as well.

Porter - As it is the weekend I should have time to see if the one currently installed has a armiture binding problem.

Must confess, my spare is not OEM but I will be placing an order for one today. And an oil pressure switch.

YAZ!

You may as well go ahead and rework the entire fuse block (should you have the time and haven't done it in a while). Chemically clean/treat the copper, clean/tighten the screw areas and re-tension the fuse holders. Let me know if you need any parts, YAZ. You'd be surprised what I have!PM me should you need anything at all.

As to the URO DME relay,....most of the time they just don't/won't last,..not sure what the problem is as I've not autopsied a failed URO DME relay. Others have had them fail right out of the box. Usually (however) they are fine for T/S purposes,..otherwise advised to have the real deal in the glovebox.

Sidebar: Helped a friend last year who was suffering intermittent issues,..he had a bunch of work done (more so) "easter-egging", only to finally discover that the issue (bad connectivity) was within the DME relay receptacle (female) side. Sure had him thinking it was the DME relay for a while!

Hope to see you soon, YAZ!

BEST!

Doyle

Rather than a spare relay, I carry a much simpler bypass wire. Not for normal use, of course, but more reliable in a pinch than a relay.

I've refined the one I now carry some, but the basics are still the same. Description starts in post #23: http://forums.pelicanparts.com/porsche-911-technical-forum/665035-dme-relay-carry-spare-2.html#post6619164

yes, but the relay is much cheaper than a DME brain.

I honestly carry two (2) DME relays (not to mention a host of other goodies-all dependent upon where I'm going). It would be good to be familiar with the needed jumper pins should Murphy show up (i.e.,: two brand new DME relays BAD).....wire will do fine there (in the emergency pinch). Additional fusing could be in order, possibly,.. you don't want to be TOO liberal when over-current conditions (uncaught ones)/overvoltage issues can take out a DME. Costly. As Rusnak mentioned "much cheaper than a DME brain".

Again: I carry two.

BEST!

Doyle

Arne,

Thanks for this idea. This is just such a irritating glitch.

The relay, like a fuse is there to protect more expensive equipment.....relays. fuses, speed/reference sensors, brake pads, 02 sensors etc are wear items.....they need occasional replacement.

Yaz,

Sure is weird to read this thread again, eh? Forgive me in reposting a piece of thread post #8:

Sidebar: Helped a friend last year who was suffering intermittent issues,..he had a bunch of work done (more so) "easter-egging", only to finally discover that the issue (bad connectivity) was within the DME relay receptacle (female) side. Sure had him thinking it was the DME relay for a while!....

...haunting, eh?

The (your) failed DME relay socket receptacle truly ends up being the source.....along with a flaky DME...

We shall be soldering very soon,.....thanks to Loren fixing the DME,..and ALSO providing us the pin needed to repair. Frikin' A !!!!!!

BEST!

Doyle

Don't be surprised if it isn't the relay or something else electrical power related to the DME.

I think you should certainly look at th relay but I'd suggest doing nothing if and when it happens again and see if it will crank and start once it's cooled off. You could be looking at CHT sensor or speed sensor issues as the symptoms would be similar to what you described.

As mentioned, Loren has corrected an IC failure within the DME. Yaz has ID'd the disintegrated female side of the socket ( I think it's running in a different thread ). So, the final (hopefully) failure point has been ID'd. The replacement part is inbound, as we "speak". The DME has been thoroughly checked out (repaired) by Loren (good-2-go) and we already know about (and will repair) this DME relay Female side issue.

In mentioning this issue (above), I would state that Yaz can get her to crank should there be applied pressure on the socket.....it's quite obvious.

Once we get this addressed,..hopefully we won't have to visit anything further. (although I completely understand what you're recco'g re: the CHT or speed sensor).

BEST!

Doyle