Glo Plug Light

1997- Present: ML320, ML430, ML55AMG, ML280CDI 4matic, ML320CDI 4matic, ML420CDI 4matic, ML350 4matic, ML500 4matic, ML63AMG 4matic, GL 320CDI, GL420CDI, GL450, GL550, GLK220CDI, GLK280, GLK350, GLK320CDI, GL350 CDI, GL400, GL500
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Max2004
Dernburg Wagon
Posts: 7
Joined: Wed 12 Aug, 2015 10:19 am
Model you own: w163

Glo Plug Light

Post by Max2004 » Wed 12 Aug, 2015 10:46 am

Hi I have just purchased a 2004 ML270CDI and its running very well. However the glow plug light stays on all the time unless I have driven for a while (about 15 minutes) and turn off motor and restart, the light then comes on for a couple of minutes and goes off as it should. Is this a plug problem or some other electrical problem?

Any advice gladly received

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Tony From West Oz
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Re: Glo Plug Light

Post by Tony From West Oz » Wed 12 Aug, 2015 10:58 pm

Generally the glow plug light should come on for a short time before cranking the engine. If it stays on or comes on while the engine is running, it indicates a fault in the GP [Glow Plug] system (usually a dead GP).
If you are mechanically minded, you can locate the GP relay and the connector which has the same number of terminals as the number of cylinders of the engine.
Using a multimeter, check the resistance from the connector to the battery negative terminal (or metal engine part). This should be approximately 0.8 ohms for a cold GP. Resistance below 0.5 or above 5 ohms indicates that the GP needs to be replaced.

I hope this helps,
Tony
Life is a journey, with problems to solve, lessons to learn, but most of all, experiences to enjoy.

'83 W123 300D 325000km (Wife's car Josephine - sold).
'84 W123 300D replaced good OM617 912 with OM617 952 and enjoyed having good acceleration for the first time since first driving a 300D in 2002 - became engine and trans donor for 300CD Turbodiesel conversion. Now parted out.
'86 W124 300D sold (Wife's old car - sold )
'85 W123 300CD, 275 000km (Fatmobile) rebuilt turbodiesel from previous Fatmobile transplanted into 280CE (SOLD)
'99 W202 C250 Turbodiesel (my darling Wife's car - Sold)
'98 W202 C250 Turbodiesel (my car - Sold)
'06 Ssanyong Musso Crew Cab 2WD Ute (OM662 diesel and Auto Transmission)

Max2004
Dernburg Wagon
Posts: 7
Joined: Wed 12 Aug, 2015 10:19 am
Model you own: w163

Re: Glo Plug Light

Post by Max2004 » Thu 13 Aug, 2015 9:25 am

Thanks for that Tony, I'll dig my multi meter out at the weekend and check them out. Just out of interest is this causing any issue with the running of the motor? No issues starting up fires first time every morning (even in the chilly Melbourne winter)

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Mercmad
Mercedes Demigod
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Re: Glo Plug Light

Post by Mercmad » Thu 13 Aug, 2015 6:41 pm

How many k's on it? The glow plugs may need changing if the k's are around 200,000. Get your battery checked too, a low voltage condition will make things like the glow plug come on by themselves.

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Tony From West Oz
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Joined: Mon 20 Jun, 2005 9:04 pm
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Location: Bedfordale WA

Re: Glo Plug Light

Post by Tony From West Oz » Thu 13 Aug, 2015 10:53 pm

Max2004 wrote:Thanks for that Tony, I'll dig my multi meter out at the weekend and check them out. Just out of interest is this causing any issue with the running of the motor? No issues starting up fires first time every morning (even in the chilly Melbourne winter)
You may wish to check out the voltage on each GP during the glow sequence, in case you have a connection issue.
As long as the engine is starting normally, then this will have no long term consequence for the engine.
If the starting gets harder, the starter motor and battery will have a reduced lifespan. You may also have a lot of unburnt fuel in the combustion chamber causing a lot of white smoke before, at and following startup.

Check it out then repair/replace the fault, so you can get back to enjoyable motoring.

Tony
Life is a journey, with problems to solve, lessons to learn, but most of all, experiences to enjoy.

'83 W123 300D 325000km (Wife's car Josephine - sold).
'84 W123 300D replaced good OM617 912 with OM617 952 and enjoyed having good acceleration for the first time since first driving a 300D in 2002 - became engine and trans donor for 300CD Turbodiesel conversion. Now parted out.
'86 W124 300D sold (Wife's old car - sold )
'85 W123 300CD, 275 000km (Fatmobile) rebuilt turbodiesel from previous Fatmobile transplanted into 280CE (SOLD)
'99 W202 C250 Turbodiesel (my darling Wife's car - Sold)
'98 W202 C250 Turbodiesel (my car - Sold)
'06 Ssanyong Musso Crew Cab 2WD Ute (OM662 diesel and Auto Transmission)

Mickey
C Class
Posts: 34
Joined: Mon 13 Apr, 2015 11:04 am
Model you own: w164
Location: Sutherland Shire, NSW

Re: Glo Plug Light

Post by Mickey » Fri 14 Aug, 2015 1:14 pm

So what is the expected life of a glow plug? I have a 5 year old ML350 CDI with just 66,000km and have had a failure of 1 plug a couple of months ago. Car still starts OK but seems to crank for a little longer than usual before it fires during winter. I thought I would get them all replaced at once in case the others are on the way out as well, which the service guy says is likely. Any experience out there?

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Mercmad
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Re: Glo Plug Light

Post by Mercmad » Fri 14 Aug, 2015 6:48 pm

All of these CDi engines rely heavily on the glowplugs to start easily so it doesn't pay to change just one. Short glow plug life is a sign of short running,that is,starting the car,driving the kids about 2KMs to school,and driving home again. Doing this a few times every day soon wears them out in a short mileage.

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pastelgrey300D
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Re: Glo Plug Light

Post by pastelgrey300D » Tue 18 Aug, 2015 4:04 pm

How many k's on it? The glow plugs may need changing if the k's are around 200,000
200000 on glowplugs is lucky for a modern car! At our last place the bloke who lived across the road had a kia pregio (preggo?) van and he was our pseudo alarm clock - every morning around 7am we would hear him cranking the bloody thing for about 15-20 seconds before it would chatter into life. Was tempted to leave some money in his letterbox with a note that read 'CHANGE YOUR GODDAMN GLOWPLUGS!' or something to that effect.

At our current house there is a family who lives diagonally across from us with a fairly recent looking Audi Q7 and that thing takes quite a few cranks to fire up and when it does it's acoompanied by a big burst of black smoke, would have to be a few glowplugs at least burned out on that engine.
David
1967 W111 230S - Horizonblau
1965 W110 190c - Mittelrot
1967 W110 200D - Weiss (work in progress)
+ other classics

frendomech1
B Class
Posts: 20
Joined: Wed 02 Sep, 2015 8:17 pm

Re: Glo Plug Light

Post by frendomech1 » Wed 02 Sep, 2015 8:43 pm

Hi replacing glow plugs on these engines are very common the 2 reasons the light will come on are a open circuit for one or more plugs or a faulty glow plug relay, I am a mercedes-benz specialist and i plug in my diagnostic scanner to see which plug is faulty or if the the relay is faulty either one will log a fault in the ecu. If it is a faulty glow plug i recommend to all my customers to replace all 6 becuase it is very common to change the one or 2 faulty plugs and a month later another one faults so i say save the hassle and replace all 6, as to how long they should last ive seen them fail as low as 50-60k and some last over 100k so its hard to say really.

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