What is a DME Relay

[Biscuit761]

Have been told that I should keep a spare Porsche DME Relay in my 968, can anyone enlighten me on what this is for and is it a regular break down item.

Bill

[turbobloke]

What is a DME relay? Probably bl00dy expensive if you need a new one. If it's the same kind of DME relay laughably called a 'switch' by my OPC, it could have a main dealer price of anywhere between £500 and £800 but they're available from independents made by the same source for about half the 'official' price.

Found out about all this when my 911T started to misfire when the car went over even a small ramp in the road. Then it cut out for longer periods, then period. It turned out to be the DME relay, a black box the size of a small modem or fat pocket calculator, sitting on the inside rear wing in the 965 engine compartment.

If you've been recommended to carry one as a spare I'm not too sure it's the same, but possible. As relays go I've only ever carried a spare fuel pump relay, and that was in a Ferrari before I learned how to hit the problem one very technically and unstick it

[turbobloke]

Update - just found this which could well be of interest.

Looks more and more like the DME relay I had fun with is different, as I'd suspected, but either way I hope yours stays OK.

[gaity]

I think the DME relay Bill is talking about IS the fuel pump relay, said to be unreliable. Costs about £20 (from Design911), give or take. I carry a spare, tucked up inside the fusebox. I may be wrong but isn't the ECU sometimes referred to as the DME? (which does cost mega £££)
Trev

[david968s]

Bill,

This is a really cheap part that is simply a relay for the DME, much as the name suggests! The DME is essentially the engine management and it controls the fuel pump amongst many other things. These relays are famous for failing on 968s and failure can lead to all sorts of ills. For instance, my car had hot starting troubles - changed the relay, all sorted. A new relay is only about £15 plus VAT - you can get one mail order from Stu on the 968uk forum - the cheapest source there is. Check your relay for the part number (it lives in the fuse box, left hand side of engine bay - the diagram on the lid should point you towards it). If it has the part number 944.###.###.### then it is the old type and it will fail at some point. If the number starts 993.###.###.### then it is the new type and you needn't worry about having a spare.

Hope that helps!

Dave

[turbobloke]

Yep, you folks are right, the link in my second post suggests it's no more than a regular relay in the nest, worthy of the Bosch hammer (small variety).

[rubystone]

What's a DME relay cost? Well £750 in my case - the amount of money I lost on selling my 3.2 when the bloody relay failed on the way to have it MOTd...which caused the buyer to back out of the deal....(I sold it the next day though - but for £750 less...)

BTW my car had been fitted with a non-Bosch one and for the sake of an extra £15 I'd rather fit a genuine Bosch part - so I'd advise you to make sure that the one you buy is genuine.

[bite-me]

Biscuit761 said:

Have been told that I should keep a spare Porsche DME Relay in my 968, can anyone enlighten me on what this is for and is it a regular break down item. Bill

The DME relay is 2 relays in one.
Looking after the fuel pump and DME. Its functions is to basically ensure that the fuel pump will only run when the engine is running, this it knows from the DME.

The DME is the electronic management system, in 86.5 > cars under the passenger side foot well.

If the relay fails, it does not take a scientist to work out the fuel pump wont work.

You can bypass the relay with 2 wires, as a get you home fix. but this means the fuel pump is permantly live so is dangerous and will drain your battery.

a good fix is to pull the relay and tap it. but its advisable to get a PROPER one from Porsche, there only about £20

I did a write-up where I converted a broken DME relay into a blank pre-wired get you home fix. Dont have detials to hand but it was published