Wtromb

Thanks to all for the tip on keeping a spare DME Relay!

I wanted to pull my 1986 Cab with 22,000 original miles out of the garage this morining and it wouldn't start. Made a quick check of the fuses, then replaced the DME relay which immediately fixed the problem.

imcarthur

I keep a spare also but haven't used it.

I wonder why the relay is such a weak link? Current draw from the pump?

Ian

Oshin11

Funny thing you mention that, the post DME and alternator problems i was having was not due to a bad fuel pump but a bad DME. Took my mechanic 5 minutes to fix. Awesome!

Steve Weiner-Rennsport Systems

You called it,...

Its current capacity is somewhat limited for the load it handles; fuel pump & DME. Add scattered quality control in the manufacture and it adds up to a life-limited part.

Bottom line for ALL Motronic-equipped cars? Always carry a new spare.

Lorenfb

"Its current capacity is somewhat limited for the load it handles; fuel pump & DME. Add scattered quality control in the manufacture and it adds up to a life-limited part."

Actually not, the real problems with the DME relay are:

1. It's mounted using a cantliever bracket which allows it to vibrate.
2. It's mounted on the floor of the car which receives most of the road vibrations.
3. It uses large relays internally which have a large mass relative to the circuit board
causing the relays to vibrate relative to the circuit board, which cause "cold solder" joints.
4. The internal relays are not soldered properly to the circuit board during manufacturing,
as is the case for the other components.

Read here for more info on why automotive electronics fail : www.systemsc.com/problems.htm

imcarthur

If it's vibration, would a rubber/foam insulator underneath improve its life expectancy?

Ian

KRA993tt

Loren,

Any recommendations for a reliable fix? Any preventative measures?

theiceman

looks to me like an ideal spot for a solid state relay, but I imagine there is more electronics involved. If not and it is a simple relay SS relays are relatively cheap and rock solid.

Spodie!

I left for a run up in the Angeles National Forest around noon on Saturday - and I just got back a few minutes ago!

The car just seemed to experience the dreaded "sudden loss of power". I switched out the DME relay with the new one I had with me, but nothing. I'm guessing it's the DME.

What a horrible experience I had with AAA. I was stranded for 20 hours up there!

Any of you guys ever tried to sleep in a Porsche with no blanket and in 35º weather? Not fun!

Off to Otto's in the AM.

J. Brinkley

I put a square of rubber with a hole for the stud under the relay. 1/4 inch I think, maybe 1/8 don't remember. Maybe it helps, maybe not.