Cold start problem

[L_A]

I have a problem when starting my car in the morning when the engine is cold was told that it may have something to do with glow plug relay and glow plugs how can i check firstly if it is the relay at fault if not then how do i test glow plugs is there any diy way to test these ?

 

[mbenz1]

A star diagnostic check from MB dealer or mercedes specialist should let you know of any problems with you car.

 

[Damien O]

The glow coil light should illuminate if there is a drop in voltage or problem with the heater plugs or relay. To test the plugs, get yourself a set of jump leads. Remove the heater plugs one at a time and grip the body of the plug with the negative lead ( you chould have both leads attached to battery at this stage ) now touch the positive lead to the end end of the heater plug where the wire screws on. If the plug is working properly it should glow up red. Do the same with the rest of the plugs.

The relay is a bit harder to check and better if you have someone near you who will allow you to swap over and try it.

 

[sspeed]

My own view is that it wont be your glow plugs..
I recon air in the fuel lines..
I have just renewed the O rings in my own car which is a 2005 with 70,000 miles on it..
Mine was very hard to start when cold, because it had sucked air into the fuel lines as it cooled down. This effectively means the engine has to crank over lots to bleed the air out before it will start.

What mileage and what year is your car ??
The O ring replacement is a common fault when the engine is around the age that mine is..
The ) rings are about £2 a piece and on my car there is 4 to replace, though its more than likely its just the 2 that connect to the hi pressure pump..
Look at my photo.. I know yours is a different engine but the principal is the same..
Is there any weeping around the hi pressure pump where the Fuel pipe joins?
If so then its more than likely your problem..
Its not that its leaking Diesel..It that its sucking air in as the engine cools..

 

[Damien O]

That's your low pressure pump pictured. But very true as I have only just replaced the O ring on the bottom of the 2 pipes. I was able to see air in top clear pipe. The o ring had gone square and hardened up. 5 minute job to do yourself but I bet a garage would milk it out for a day or two trying to find the problem.

 

[mersum1es]

OP: what's the model year of your car (is it I6 or V6 engine?).
Like above star will tell if there is clearly faulty parts, and rail pressure can be observed when cranking. If low rail pressure, o-rings (like above), rail pressure sensor, rail pressure regulator, hp-pump itself.

Faulty glow plug should always put the light on after start. Is that happening? Faulty relay is not always giving any sign. I6 engine starts fine without couple of glows, V6 engine is bit more sensitive.

 

[andymerc]

The v6 sometimes need both control unit and glow plug ,they do need glow plug working to start unlike the older engines that would start ok with glow plugs not working.

 

[kubi]

Hiya,

Thats really interesting. I have a 2005 W164 ML320 and it turns over for about 5 seconds before firing. Although it always starts its a bit annoying. I was going to change the set of glow plugs as they dont seem to expensive to do. Is it worth changing the O'rings as well??

Which Glow plugs are the best to buy?

Cheers

 

[L_A]

Mine is a V6 e320 cdi, its really bad when very cold and i have to leave it for a minute or so then try again, if it takes more then about three trys to start i do notice pools of smoke out the back. i think all this is putting a lot of strain on starter etc so will get it seen to soon

 

[cwpaters]

I am having the same problem Kubi on my W164 ML280, I wanted to try giving fixing it myself first before i resort to a MB dealer! Have you tried anything yet?

 

[kubi]

Fixed!!

Hi.

I had a garage change the glow plugs and all is well