300d non starter 1992

[cranked]

hi guys, really glad i found this site as your my last hope, my w124 92 300d was getting very hard to start as the weather was getting colder ,the glowplug light light comes on as normal for 15/20 secs then goes out i then try to start it it just turns over and over until the battery goes flat, it has been fitted with new oem glowplugs and a new relay , i have discoverd that the relay solenoid inside does not activate on the new or old relay when the key is turned on (ie it remains in the open position) there is power to the relay (thick red lead) but it does not operate! any help or clues will be much apreciated maybe engine temp sensor/ignition switch/another fuse or relay somewhere, the fuel system has not been disturbed at all and the car will start first time with the aid of easy start although i don't like to use it.: thanks in advance gary.

 

[Bolide]

Glowplugs

Are the glowplugs working or not? Can't really tell from your post. Stick a meter on one and see or pull the multipin plug off the relay and put a meter on the outputs to test them

If the glowplugs aren't working, and the relay's getting power, then it can't be switching. IIRC the dash light is fed from the relay, so if the dash light is doing the right things I don't quite understand what's happening

You'll have to locate the feed that tags the relay. It'll run from the ignition switch to the relay and may supply 12V or put an earth on the relay depending how the relay's wired

Assuming the ignition feed supplies 12V to the relay you can test it like this: If the engine's cold, try turning on the ignition and the headlights. If the relay is tagging, and the plugs working, the lights will go dim & then get brighter about 90 secs later as the relay turns off. If this isn't happening try jumpering the battery 12V to the relay turn-on with a length of wire. If the relay tags & lights go dim then you've found your wiring fault

BTW If neither relay tags then the original relay is probably OK. And whoever did the original fault-finding & fitted the new relay did a poor job!

Final thing: is there an immobiliser fitted??

Nick Froome
www.w124.co.uk

 

[cranked]

300d non starter

hi nick thanks for your reply,
no the plugs are not working and the relay is not tagging or operating (what does iirc mean) , gary. (vwgolfgtimk1) track day car..........

 

[Bolide]

Glowplugs

IIRC = If I remember correctly

If the relay's not tagging follow the instructions to test. Assuming you get the relay to work, check the colour code of the "bad" wire on the relay and check for it at the ignition switch and test there with a meter

As I recall it's not a direct cable from the switch to the relay - there's quite a complex set of conditions to be met for the starter & glowplugs to be activated and it may be that the fault lies somewhere along this chain

You may find it useful to download a PDF of the starting circuitry from the web - look at www.diakom.ru for 5843.pdf. This may be relevant

Nick Froome
www.w124.co.uk