270 CDI Glowplugs (W163)

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michael8554

Active Member
Joined
Mar 2, 2006
Messages
103
Location
Wiltshire
Car
(ML270CDI, A160 W168) - 2007 A150 W169
Noticed that the glowplug light on the instrument panel hadn't gone out after the engine had started.
First off dabbed a wire from the battery positive in turn to the tip of each plug.
Found one that didn't give a spark.
Measured that one with my multimeter and found it was open circuit, luckily this was the easiest plug to access on the engine.
The others were about 1 ohm.
Checked the glowplug relay and found all 6 outputs were okay, not suprising as the plug had gone open circuit not short circuit.
Bought a 10mm 1/2" drive deep socket, a can of unlocking spray, and a new Beru glowplug.
Make sure the socket is deep enough to go over the top push-connector section and fully engage the lower hexagon section on the glowplug, even when attached to your 1/2" drive t-bar or torque wrench.
Applied the socket with a torque wrench on a warm engine.
The plug clicked and started to turn at about 20ft/lbs, and unscrewed and pulled out easily.
Didn't need the spray can.
The old plug was Beru and marked A001 159 49 01 on the shaft, the new Beru was 0100 226 379 on the box.
This was only the second fault in the 3 years I've had the car, at 44K miles now.
About a year after I bought the car the gearbox lost drive halfway through an overtake, very scary.
Pilot bush was leaking so replaced and ATF and filter renewed and okay since.
Also learned from reading this site that glowplugs are only needed in cold weather.
I've been religiously turning on the ignition and waiting for the glowplug light to go out and only then have I started the engine.
Thats a few thousand heat-ups I could have avoided it seems.
 

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I think even you won't wait the pre heating time of your engine, it does it wanyway after start (light just go out but heat remains)...
 
Not sure mersum1es, the light going out when the engine fires might indicate that the current has switched off, instead of staying on for the usual 4 seconds or so.
 
Not true with newer engines, this is from 651 engine manual:

The electronically
controlled Instant Start System
consists of a glow output stage and four ceramic glow
plugs. The Instant Start System allows the engine to
be started immediately without preglowing at high
coolant temperatures. In order to improve the cold
start and warm-up characteristics of the engine, after
-glowing is performed in steps via the controllable glow
temperature. The CDI control unit regulates the
voltage at the glow plugs via the glow output stage
depending on time and temperature.
This has the following advantages:
• Short preglow time
•Stable idling
• Low exhaust gas emissions
• Good response behavior
• Controllable glow temperature

Preglowing
Preglowing warms up the combustion chambers of the
engine so that the required ignition temperature of the
fuel/air mixture is reached. The CDIcontrol unit first
evaluates the engine oil temperature and then actuates the glow output stage
via the drive LIN (LIN C1)depending on the coolant temperature.
A prerequisite for the preglow is a coolant temperature below 30°C

Start-ready glowing
The start-ready glow function provides a sufficiently
high temperature after preglowing until the engine is
finally started. To achieve this, the glow output stage
actuates the glow plugs. The preglow indicator lamp
goes out once a start-ready temperature of 1,250°C
is reached in the glow plug

Start-up glowing
Start-up glowing stabilizesthe starting speed of the
engine. When the CDI control unit receives the information "Circuit 50 ON" from the electronic ignition lock control unit,the glowoutput stage actuates the
glow plugs via the drive LIN, thus supporting the first firing strokes and engine start-up

Afterglowing
Afterglowing improves engine running after a cold
start and the warm-up characteristics of the engine.
The CDI control unit evaluates the engine oil temperature and actuates the glow plugs via the glow output stage after the engine is started. Afterglowing is terminated once the coolant temperature reaches a specified value


So after glow at least is not shown by light, I could dig WIS document about 612 engine

 
Last edited:
Now I'm confused.
Does this mean I should wait for the glow light to go out after all?
Michael
 
Yes, I think if you do it, it actually is better for your engine. Even you'll start the engine immediately without waiting, glows are on according the engine temerature/conditions, so you are not 'saving' anything.

When it's said 'does not need glow plugs', only means that engine will fire withing nearly same time, when compared those 'old school' diesel which wouldn't.
 

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