diesel starter coil light

Hi all
I'm very non techie so please excuse the prose explanaation.
y'know the diesel warm-up light on the dash (coil figure) that takes a few seconds to go out before you can start the car - well it has started coming
on when I am driving. Only for a minute or 2 but I'm sure this is not meant to happen.
does this mean a coil needs replacing?
any advice appreciated
bronach
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On Fri, 21 May 2004 9:23:38 +0100, bronach wrote:

[[[Caveat: I am NOT a diesel fitter, nor do I drive a diesel car]]]
Diesel engines have what are known as glow plugs. These heat up when you first start the car to make the diesel easier for the engine to burn (they actually live inside each cylinder in much the same way as spark plugs do in a petrol engine). The ldash lamp that you describe sounds like the glow plug warning light - to let you know when the glow plugs are actively heating the cylinders.
There's likely to be a temp sensor to tell the glow plugs when they are needed, if they are coming on when the car is hot, I would guess that this temp sensor isn't playing the game properly - that's my guess, what about everyone else?
300Essie
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1994 Mercedes E280 [W124] 99,000 miles (R.I.P)
1992 Mercedes 300 SE [W126] 230,000 miles
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I recall from my manual for my 190 D 2.5 diesel 1987 that the light comes on, on later models (than mine) when the glowplugs needs to be changed. It is a warning that comes on saying much the same as when the oillamp is is on that oil needs to be refilled. So my recalled guess is that the glowplug is near its end and needs a replacement - all 4 or 5 of them would be a good thing.

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I do not think you are right in what you suppose. I will explain why... Glow plugs are only fitted to indirect deisels. With these sort of engines there is a combustion chamber apart and to one side of the cylinder where the injector sprays.
With this sort of engine if the glow plugs are at all defective it will be very difficult to start if at all.
The original poster did not state that his motor car was difficult to start, simply that he was alarmed that the glow-plug light was coming on after the engine had started and he was cruising.
I have had the same intermittent problem , and have found that the light goes out at the end of the glow-plug maximum time allowed. With me it has been an occasional occurrence, and I have not done anything to fix it as the glow plugs coming on does no harm to the engine. There is obviously something adrift for them to come on, or the light to come on, or both, but as it does no harm, other than being slightly irritating, I do not think it an issue of concern.
One could spend hundreds of bucks sorting the problem out, or one could just leave it the way it is, so long as the engine is starting-up on the key as it should.
Depends how pernickity one is, and how deep the wallet can extend to sort unimportant problems....
On the other hand, a chat with the local Merc dealer may disclose a simple fix that he can do himself. Might be worth talking to them. It is certainly a known problem. But do not let them sell you a new set of heater plugs if the car is starting as it should do. It will not start satisfactorily if there is anything wrong with the plugs themselves.
Hope this helps,
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All the best,
Stubbsy.
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start,
Yes, sorry there - my mistake. My mb manual says conterary that "...if the glowplug does not light up at on trying to start all there is an error and an mb serviceshop should look at it."
My Haynes manual says:
Testing glowplugs:
- put a voltmeter on the plusend of the glowplug and the other to the ground on the car. - let a person turn the start-key and note if there is voltage - if it works then volts will rise towards heating up and will turn to zero when the heating stops.
- If voltages is lacking and don't show at al then the glowplug is defect or the relay is defect.
Could be the relay control - a loose wire perhaps in the relay.
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When this happend to me, it was the Glow Plug relay had failed. I didn't like to let it go, because the Glow plugs were actually engaged. As this is a part that is only supposed to see use at start-up, I didn't feel comfortable letting it (them) heat up on thier own when they weren't required figuring it would lead to early(ier) replacment. Regards Ken

coming
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I agree. Had the glow plug light on an old Volvo diesel come on while driving, the relay was crap. Replaced it, problem solved.
Careful about letting this slip, having a glow plug melt off inside the engine is absolutley horrible, so are stuck swolen plugs and the ever present fear of melting the block.
-Mike

few
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Hi hade the same on my 220d
it can be one of 2 things
1. the pree heater relay sensor/ solenoid cost about 90.00 this pree heats the desel and the glow plugs
2. the glow plugs need replacing cost from 10.00 each GSF to 25.00 each Halfords.
regards
Guy
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