My 240d only clicks when I turn the key. Sometimes the dashboard glow plug light comes on, sometimes not.

The clicking is coming from the glow plug unit under the hood.

Do I need to replace the glow plugs, the relay, both?

Anyone have experience with this?

Thanks!

Lots of possibilities here: bad battery, bad key switch, bad starter, bad connections, bad solenoid etc. Start by testing the battery with a load tester.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Welcome to the forum!

I'd start at the battery. Clean all the terminals, check your voltage, and make sure the connections are tight. Make sure to clean both ends of the ground off the battery. Check the ground strap from the transmission to the body under the car. Clean all the contacts and make sure connections are tight. Then check all the wires on the starter. Make sure the connections are tight, and try cleaning everything with a wire brush. See if that will start it.

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Thank you for the replies.

All of my battery cables look good and are tight, no corrosion at the poles.

I took the battery to Advance and it tested at 675 of 750 capacity. I'm putting it on my home battery charger to top it off.

Do I proceed to the glow plugs now?

If the charged battery turns the engine over then move on to the fuel and glow factors. If not, you might want to check the connections between the battery and the starter.

Battery and starter connections are secure, but battery does not turn engine over. The glow plug light is coming on.

Take out the starter/ solenoid and test?

That would be my next step.

Might want to just try tapping the starter with a hammer. May just be caught.

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Codifex
1981 240D ChinaBlue (Got her running with a donor engine.)
1983 300DTurbo w/sunroof.
1984 300TD manual sunroof. (Electrical Gremlins)

That happened to me one time. I cleaned and tightened all the connections...took out the starter and brought it to crappy tire to have the guy test it for me. He told me the starter was no good and sold me their top of the line model.

I took that new starter home put it in and got the same clicking sound when turning the key. It turned out that the ground cable was broken inside the rubber wire insulation from the battery to the body. It was a fairly heavy ground wire too. You could'nt tell by looking at the wire that there was anything wrong....but it showed with continuity tester. Sometimes if you bent it the right way then I could get continuity but that won't cut it to draw power to start. Replaced the ground wire and the car started.