W203 Sam says faults on all 4 glow plugs

[Halfasheep]

Hi guys, got a 2001/51 c220 CDI.

Got a misfire when cold, been on Star and garage says there's faults showing on the 4 glow plugs on the SAM.

When it's warm the misfire goes away. Initially thought it might have been an injector fault.

Garage said it's nothing to worry about!

I know I've read elsewhere that the fault might actually be the glow plug relay?

Any thoughts? I'm new to MB ownership so I figure you guys will steer me correctly

Not got any fault codes (I didn't pick the car up from the garage and the missus forgot to ask)

Thank you

 

[mersum1es]

If 'misfire' is happening all the time when engine is gold, is definately is not glow plugs. It may struggle to start and have hunting idle fow few seconds but...

You can measure plug+wire resistances from plug controllers connector. W203 contreller 'fuse bridges' are easy to check and somehow repairable.

Misfire is probably due to injector. Sounds like you have to find a better garage. Owning a Star won't make you top MB Mechanic

 

[Halfasheep]

If 'misfire' is happening all the time when engine is gold, is definately is not glow plugs. It may struggle to start and have hunting idle fow few seconds but...

You can measure plug+wire resistances from plug controllers connector. W203 contreller 'fuse bridges' are easy to check and somehow repairable.

Misfire is probably due to injector. Sounds like you have to find a better garage. Owning a Star won't make you top MB Mechanic

Thank you. I know the car doesn't suffer from "black death", so I wonder if an injector is leaking fuel.

Will find an indy nearby.

Thanks again

 

[mersum1es]

Black death if totally different thing that injector leak I referred. That leak is spill of tank line leak, which is natural for all injectors. But when leak goes excessive, fuel pump cannot build pressure during crank fast enough, and car won't start. That is pretty easy DIY test, lotsa pictures, threads on forum plus youtube videos.

Edit: You engine do suffer o-ring problems (do a search about that too), and there you should see air bubbles running in clear fuel lines.

 

[Redman99]

This looks like the most recent thread on a W203 (actually a S203 Estate in my case) and glow plugs. I am also suffering difficult starting and its not the battery and does not seem to be the starter motor. I checked the GP relay housing and there is power coming from all 4 male connectors; but when I tested the female (ie to the GPs) side I could only find continuity on Cylinder 3 - the other 3 do not respond. I assume this is a reasonable test of the wiring to/from the GPs and of the GPs themselves? Grateful for any advice: I appreciate the next step is to clear a path to the GPs and try to get them out and test them directly, but I'd like to avoid that if possible!

 

[BTB 500]

Yes continuity across a plug should indicate that it's OK. If there's a problem with a plug (or the wiring) this should show up on STAR diagnostics (which will identify the specific plug/plugs).

Normally if there's a failed plug the glowplug light on the cluster will come on for a minute or two immediately after starting (my S203 was petrol but AFAIK this is standard behaviour for diesel Mercs - it's certainly what our Vito does). And as an aside the glowplug light coming on while driving usually indicates a relay problem.

 

[Redman99]

Yes continuity across a plug should indicate that it's OK. If there's a problem with a plug (or the wiring) this should show up on STAR diagnostics (which will identify the specific plug/plugs).

Normally if there's a failed plug the glowplug light on the cluster will come on for a minute or two immediately after starting (my S203 was petrol but AFAIK this is standard behaviour for diesel Mercs - it's certainly what our Vito does). And as an aside the glowplug light coming on while driving usually indicates a relay problem.

Well the GP light does come on and stay on for a short while when starting in very cold weather, though once it goes out it does not reappear. I'll start spraying the GPs with releasing fluid!

 

[BTB 500]

I'll start spraying the GPs with releasing fluid!

Once you've got direct access to the plugs you should be able to test them (for continuity) without taking them out? There's always a risk of them shearing off.

 

[ALFAitalia]

Test resistance between the tip of the glowplugs connector and right next to it on the head....should be about 2 ohms.....my last faulty one read 64 ohms!