DME Mysteries

[g59tester]

Hi Guys , Am I having more DME issues?
At the beginning of August the car wouldn't start. turns over OK but not a cough out of it. I replaced the DME relay with one from Design 911 which is described by them as "964/993/944 fuel pump relay 'OEM Brand' " cost £30.41 +Vat plus postage total £43.63.. I know they have a cheaper one and a Porsche one at 'twice the price'.
Car started immediately. I've possibly started the car about 8 times since 3/8/21

Today car wont start again.... similar symptoms.
Are these relays really that fractious?
I have another relay which came with the car in a DME box marked 'spare'. Terminals 2,4,and 8 have been shorted out externally. Not knowing the status of this relay i'm reluctant to try it out despite the fact that i wanted to attend a local car show on Sunday. I've ordered another relay from Design 911 but it wont be here till Monday

Anybody got a test procedure to prove the 'new ' relay is faulty?

Eddie
1988 944 Turbo
2007 Cayman S

 

[Waylander]

The really is shorted out in the pattern of the three wire jump, which basically bypasses the dme relay

this relay is used to switch the fuel pump on when the signal from the ecu is triggered by the engine reaching 200 rpm

you will not do any damage by using that jumped relay, it will just turn the fuel pump on permanently

 

[BenEngland]

Hi.

There is a useful description of the operation, testing & repair of the DME relay on the 'Clark's Garage' website.

http://www.clarks-garage.com/shop-manual/fuel-05.htm

Hope this helps

 

[vitesse]

I use a PP9 battery with 2 short leads terminated with insulated Lucar connectors-the twin "press stud " PP9 connector is available on-line.
Just connect to one terminal on the relay (No 30 battery input ) & touch on the other appropriate terminal -86,I think & you should hear the relay click shut,-the circuit is normally shown on the black plastic case.
With care you can ease this case off the relay-you can then see it operate,clean the points with a thin point file or nail file with fine wet& dry wrapped round it etc.
With a small switch inserted in one of the leads ,you can then check each output using a simple test lamp or multimeter.
I did share a useful relay guide & Bosch wiring reference leaflet on here 1 or 2 years ago..

 

[g59tester]

Got the replacement relay from Design 911. stuck it in the socket and car started first time. The guy at 911 has said he wants me to send back the one that lasted 3 weeks and about 8-10 starts and hopefully he'll supply another FOC so that i have a spare. I've still after all that got 2 duff ones that came with the car so I'm going to take them to bits......

Had to take the Cayman to the Tewkesbury classic car show instead. managed to pick up an unboxed 1/34 model Cayman in matching Guards Red for all of £2

Only other 944 I saw was a late N/A 944 in a very pale metallic green colour ... in very nice condition Another Exile Scot now living in Wales
Thanks for the reponses

Eddie
1988 944 Turbo
2007 Cayman S

 

[Djsim155]

Hi all,


hoping for some advice…?

I have problems with my DME relay too.. some have mentioned solid state relays, some jumper by passes and various models and brands of DME relays..

after my car is hot, it doesn’t want to start…, sometimes from cold…, I’ve had to remove the DME relay and slot it in and out of the socket to clean the terminals… then it starts..

my relay has a small wire fixed to it…is this correct… ? The other end of the wire goes underneath the main board… no idea where after that….the pictures I have seen for replacements… don’t seem to have this wire attached for me trying to buy a replacements…?
I have an H plate 91, S2.

I like the jumper idea, that seems to remove all issues ?

what should I be doing please..? Can I upgrade things…?

My current one has part number on the top of 993.615.227.00 SHO and then on the side it has the same description as on the Frazerparts 12v max15a, PA6-GF30 made in hungary, 498132 with wiring diagram. Also has 898892000…

many thanks

Highlander

 

[Dan944t]

hi Highlander,…

i would suggest looking at the clark’s link Ben England posted above,… if you have a multimeter set it to ohms and follow the procedure ,…for the sake of what they cost new from frazerpart i think i bought a spare recently when i suspected mine to be playing up,…can’t remember now but sure it’s under £40 delivered ( bought so much lately i can’t remember )

i tested mine with a spare car battery i use for the timing light ,..and mine worked out to be within spec ,…yours may have corroded or oxidised internally or dry joint,….these are old units so inevitable espeacially if any moisture gets in it. you can make up the jumper cables , also in the clark’s and prob on that link too ,… very simple with some decent gauge wire and x3 spade connectors … i made a nice set soldered and heat shrunk ends for an emergency ,… i sugest if your up to that to do same and keep in glovebox and hope you never need it

ps. to get you out of trouble the jumper cables are ace ,.. but i don’t recommend it for a permanent fix as all you need is a new relay which isn’t expensive for what it controls…. i think as Martin said they are designed to come on at something like 200 rpm when it’s picked up by the flywheel teeth so that in an event of a crash and the motor isn’t spinning the pump cuts out as not to continue pumping petrol if the worst was to happen ( if you know what i mean)

best of luck
Daniel

 

[Djsim155]

I have since found out that the wire I have coming out of my relay is not standard… it disappears under the board that the relays and fuses are all plugged into. I have managed to borrow from a friend his spare for his dme relay for his 944 s2… his spare part number is 99361522701. Scared to try this until I work out the wire.. thinking if that’s a live then I need that disconnected first before I try the spare…

my buddies current DME relay is the F9T solid state relay with part number…F9T-ssr-993(pump prime) .Rev2 HD….. I am thinking this is the ultimate way to go…

currently awaiting my auto electrician to assist me… scared to tackle myself…

thanks
Highlander…