The car started a little funny yesterday and today, and the glow plug light comes on even after the car starts. I looked at the metal glow strip fuse in the engine compartment and it's fine. The manuals says the "preglow system" needs attention.

1) couldn't that also be from a glow plug gone bad? Or maybe they're all needing to be replaced.

2) The glow plugs were replaced about 5 years and 40,000 miles ago. How long should they last? Seems like I should get at least 12 years out of them, but maybe not.

3) If it's not the glow plug, what else could it be? I was told the preglow relay might need to be replaced, a $200 part. Is there some way to fix it, or maybe it's dirty and not making a proper connection?

1991 300d, 195k

Very likely a tired glow plug. Pull the bigger connector at the relay and test each pin for continuity to ground. IIRC, should be 0.7 - 1.0 ohms each.

Sixto
MB-less

I looked at one place a Hella 0075459932 Glow Plug Relay was listed as $124; but they said they were back ordered.

It also shows that you should have the Bosch 80031 Glow Plugs (that are 2mm shorter than the Bosch 80006 Glow Plugs) for your year and model. I beleve those are the Glow Plugs for a Glow Plug Relay that has the afterglow feature but I am not sure.

If your Car has the Relay with the afterglow feature the light should come on for a while after starting based on the input from a Coolant Temp Sensor.

But, someone who knows more about the afterglow feature needs to chime in.

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84 300D, 82 Volvo 244Gl Diesel

It has afterglow but the glow light should stay off when the engine's running.

Sixto
MB-less

Thanks for the Afterglow info.

He did not say he had trouble starting or there was a mis, nailing or so on indicating their might be a bad Glow Plug.

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84 300D, 82 Volvo 244Gl Diesel

Afterglow can mask lazy glow plugs with the rest of the cylinders running more smoothly than without afterglow right when the engine catches. If the glow plug is slowly fading and the weather is warming, you might not notice it in a daily driver.

Sixto
MB-less

I edited my original thread to add that in, the car did start funny yesterday and today, and both days the glow plug light was on after the car started.

Do the continuity test. If you can get to the bad plug easily, replace the bad plug. If you have to remove the intake manifold for access, replace all the plugs.

Sixto
MB-less

I have a similar problem in a 83 240D. The glow plug lite came on intermittantly after the engine was warm which blew all 4 glow plugs. I replaced the relay and the glow plugs, drove the car about 3 miles and the lite came on again. I turned the ignition slightly to the left but not enough to kill the engine and the lite went out. so I drove back to my shop. I'll see tomorrow if they are blown again. When the key was slightly to the left some of the gauges didn't work. Any suggestions appreciated.

Bad ignition switch.

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1981 300TD 310k miles
1970 280sel 172k miles
1966 230 Fintail 162k miles

"Where are we going? And why am I in this hand basket?"

x2 IIRC the 616 glow relay has no warning light feature once you turn the key to start the engine.

Sixto
MB-less

Re: glow plug lite comes on after engine warm. A friend suggests try replacing the coolant temp sensor. Does anyone have experience with that?

Did you do post #2? That should identify your issue. Coolant temp sensor controls duration of the pre glow which is not your problem. 7 years is about the maximum run for GPs on my car 602 engine. So at 5 years likely its a GP.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

Thanks dieselbenz1 for your response . Glow plugs and relay are new, lite still comes on after warm up. I'm thinking ignition switch because jiggling switch puts out lite. seems to be 2 possible parts, any one have a part # [1983 240D]

Does the light come on during the glow cycles as it should?

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92 e300d2.5t
01 e320
05 cdi
85 chev c10