Hi there,
I have a 1998 E300 turbodiesel elegance.
The car starts at the first twist of the key after the glow plug indicator exstingushers.
However the glow plug light then becomes immediatley lit up and stays lit up until I switch the vehicle off.
The car drives without any problems.
Anyone know what is going on please?
I have a fuel leak at the delivery valves which I am addresssing tomorrow, so obviously anything I can do while the air intake is off to fix the glow plug problem would be good.
thanks for listening.

I would check the glow plug relay...hopefully it is just the light that is on and not the GP's themselves that are on. They won't last too long like that.

Usually the GP light comes on to indicate a problem with one or more GPs but then it blinks if I am not mistaken...I don't recall anyone ever asking about a light that comes back on and stays on like this one.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

I don't believe it will blink. I had one totally "open" and one that was weak (dull red) and the light only came on continuously.

Here's something interesting about how the condition of the plugs is monitored. Scroll down to Preglow time controlhttp://mb.braingears.com/W210/w210/engine606__97changes.htm

Easiest way to check the plugs is by disconnecting the harness at the relay and doing it from there.

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2005 Pathfinder LE
2001 E55
1998 M3
1982 320i

firstly thanks for your advice guys.
ok here is how it is now.
I removed the intake manifold( what a pain ) then I checked the glow plugs for resistance via the multiplug at the relay. All registered 0.5 except one which registered 0.7.
I guess they are all ok, I didnt expect them to be faulty as the car starts at the flick of the key.
Cable continuity checks out and the voltage to the relay checks out at battery voltage.
The relay switches off at the correct interval.
HOWEVER the glowplug light illuminates when the car is running, I find myself in a predicament. NO inlet manifold on the car etc so I feel I cannot start the car to check if the relay reactivates!
Anyone know how I can check that ?????
Is it known for the relay to re energize after startup?
thanks in advance guys.

If it was my car and I had the manifold off, I'd remove each glowplug and test it to see that they all glowed bright orange. My multimeter only showed ONE plug bad and didn't show the one that was weak (dull red). I used a set of jumper cables as my "test fixture". This being said, be aware that a few folks have had trouble removing the plugs. The tips seem to carbon-up and foil removal. Before removing mine I soaked the outside of each plug with PB Blaster overnight. Mine came out at 60000 miles with no problem and I'm sure they were the originals.

If you start the car without the manifold reinstalled you'll set a code as the MAF won't be doing its job. Have you checked the OBD II interface to see if you have any codes?

As far as for checking if the relay is reactivating, after you reassemble, start the car and get it up to operating temperature and THEN disconnect the plug at the relay to see if the plugs are still getting glow current. Be sure you use an ammeter in series to see that they're getting a fair amount of AMPS. They obviously shouldn't be if the engine is hot.

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2005 Pathfinder LE
2001 E55
1998 M3
1982 320i

Thanks for the reply and advice, I must say it is refreshing that people want to help. (unlike my mercedes dealer!) advice is free here but alas mercedes dealership advice seems to cost or is non exsistent.
Anyway, ODB interface, I am afraid I cant look at that as I have no code reader.
The car computer is the updated version 1999/2000 model. with respect to that the car sometimes tells me it has an instrument cluster fault and a oil sensor problem.
I figure the oil sensor problem is happening as the leak from the delivery valves on the injector pump runs down onto the sensor!....hopefully easily solved. That is an intermitent problem.
I am going to take your advice and remove the glow plugs, I agree totally that while the manifold is off it would be prudent to remove and check.
I will keep you informed.
Cheers

well its been awhile now but I have changed the o rings and copper washers in the injection pump due to a leak;
they are fine without leaks.
While in that area I changed all the hard plastic see-through lines too.
All went well.
Then it came to the real reason why I was in that area....the dreaded glow plug issue.
So I covered the glowplugs in penetrating spray for 2 days 3 times a day.
I then set out on my expedition into the unknown. i.e. the removal!!!!
Well I broke the first one!, I twisted the head off the plug.
O.k. time to check wht MB would charge to replace them. That was when I had a shock.
if the plugs came out all ok, then it would be the cost of the plugs plus the labour at 95 pounds per hour.
Well not too bad I thought, probably be around 200ukp.
How much I asked if they didnt come out easily?..................600-800ukp!!!
well I knew I had damaged one so it would be at least 600.
So I thought what the hell, I will give it ago.
The next 2 plugs came out easily, the next one took 2 hours of careful manipulation too and fro.
I damaged another, the old head twisting off thing again.
So 3 out of 5 so far. I left the plug near the firewall until last as I would have to remove parts of the car I hadnt a clue how to remove.
I then thought how to tackle the damaged plugs. The answer was simple I knew MB had a glowplug remover/repair special tool......cost here was 409ukp, but they wouldnt sell me one anyway.
BUT............I had the WIS so I had a look at the tool and what it contained.....to my suprise it contained a set of taps/punches and a helicoil set.
I armed myself with the taps and began the drilling process.
Now the trick is to start off in the center and the centre core is perfect centre. If you can grind this off INTO the ineer casing you are laughing.
however I wasnt so lucky but got there n the end.I eventually took out 80 percent of the plug with the drill then tapped a hole to accept a 7 inch bolt which I screwed in.
I then used a claw hammer; well the claw of it to hit the head of the bolt and it eventually came out to my relief.
The second damaged one took longer as I messed up and ended up using a helicoil to repair the thread.
I think it has cost me around 200ukp including the plugs.
better then 600-800ukp at MB.
I didnt replace the plug near the firewall as I couldnt go through the trauma again. It checked out ok with the meter.
Funny thing is there was NO carbon in the threads at all!!!.....which I thought would be holding the plugs.
NOW the damn glow light still comes on and stays on after startup. The relay is working perfectly............
Any suggestions now?

Did you ever solve this problem? My 1998 Diesel 300 glow light comes on goes off as usual and the car starts immediately. A second or two later the light reappears and remains on until I stop the car. No one ever replied to my post, so I am very curious what your problem was due to. Thanks.

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1991 300D 172,000 (totaled)
1998 E300 Turbodiesel 82,500

Is your check engine light illuminated as well? Mine had a bad glow plug and the coil light would re-appear after starting accompanied by the CEL and the associated message on the data display. I tested my relay by opening both the hood and the driver's door and grasping the relay in my left hand, I stretched my right through the open door to the ignition and switched it on so I could verify the relay clicking from the feel. Of course, in the UK, you'll have to elist the help of one of your mates as you have RHD.

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-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

Yes, the CEL comes on with the message check engine electronics

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1991 300D 172,000 (totaled)
1998 E300 Turbodiesel 82,500

Which code?

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Besides the dealers loss of $$$ for free advice they could possibly be held
responsible in a law suite for advice that they give. Another problem is that customers are often not able to give you the correct information you need to give advice.
On this site there are a lot of "heads" working togeather and a lot of experiences to draw from and there is time to have you check something and come back with the info. and for more advice.
Don't blame the Dealer for protecting their business interest.