Just installed a new water pump in my 81 240D to fix the coolant leak.

Every now and then when I go to start my 240D the glow plug dashboard light won't light up and if I wait the 30 seconds the car is very hard to start. I'm thinking that the relay isn't working, but I'm not sure, could also be bad glow plugs?

I see that there are two relays in a box in the engine area that have part#001-542-0219, what are these?

Thanks,

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1981 240D
Click Here To See My Mercedes

http://www.dieselgiant.com/glowplugrepair.htm

Read this carefully first, print it out and follow the steps in order. If you don't already have one, go out and get a cheapy multimeter -- $5 at Harbor Freight. You'll have the issue sorted out in no time.

My money is on 1 or 2 bad glowplugs.

On the otherhand an old intermitent glow plug relay is far from unknown. Use a voltmeter as mentioned to establish one way or another. If thats what it turns out to be a used unit from a salvage yard shoiuld get you by.
Very few 240ds are scrapped because of a bad relay in my opinion. Remember that watching the ceiling light as an indicator is a good ideal as well. When the glow circuit is activated the light should dim a little until the relay opens up again.

Try opening the relay and cleaning the contacts...you have to pull the case apart.

So those two relays in the box are for the glow plug system?

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1981 240D
Click Here To See My Mercedes

The only problem with t-shooting just the relay is that you'll have to recreate the problem of the light not coming on and then be very, very fast to hook up the voltmeter before the glow cycle ends and the power cuts to the relay. I think troubleshooting the rest of the system first (plugs, wires, fuse) will be alot easier and if they all test out ok, then you know to start looking hard at the relay.

Good tip about the dome light. You can also hear the relay click on and off if you have the hood up and the window down.

The dash light being out does not necessarily mean the relay is not working and the glow cycle is not happening.

So the relay is under the dash? Is this a plug & work type of thing? I just unconnected it and plug it back in and it works?

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1981 240D
Click Here To See My Mercedes

Yes it is, up in front on the drivers side, it's black, has an easy lift off cover on it, and it is about as big as 2 packs of king size cigerettes. The strip fuse is very visible when you lift off the cover. There should be four wires coming from the relay and going directly to each of the glow plugs. Check out Diesel Giants work on checking the glow plug system. You'll be happy you did.

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Junqueyardjim
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis



1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!