W124 2.5 multivalv only starts on jumpstarting

[GDSP]

Hi guys, need your help please, my merc w124 2.5 diesel multivalv doesn't starts on its own battery, battery is fine, i put another one just for testing and it won't start. Strangely if I use a booster to jump start it it starts in a snap ! But then it runs rough, low power high smoke and tries to stall, engine noises... If I turn it off it won't start again until I use the booster to start it! I noticed also that sometimes the dash light of the glow plugs doesn't turn on, but if it does it won't start all the same... I tested the glow plug relay and I have voltage on all 5 connectors. I'm really lost here, I also have an Toyota Avensis Diesel that had the same symptoms and after replacing the relay it resolved the problem, but the relay was dead Wich is not the case with the merc! Thank you all!

 

[GDSP]

Just started the car with the booster and noticed that when I remove the booster the engine started nocking, if I connect it again with the engine running it stops the noise and runs like a clock!

 

[GDSP]

I'm starting to get crazy

 

[Ted]

Is the booster directly across the battery?
What is the voltage across the battery both cranking and running, booster connected and disconnected?
Sounds like it may be a faulty chassis to engine earth, but the above tests should confirm.

 

[GDSP]

Is the booster directly across the battery?
What is the voltage across the battery both cranking and running, booster connected and disconnected?
Sounds like it may be a faulty chassis to engine earth, but the above tests should confirm.

Thanks for the help, 14,10v without the booster connected, 14,24v with the booster connected , 13.09v on the battery with engine disconnected, I'm connecting the booster directly at the battery.

 

[Ted]

What about cranking voltages?
Across battery without booster
Across battery with booster
And importantly battery positive to clean point on engine
And if you can get to it, main starter terminal to clean engine point.
All whilst cranking.
There should be no more than 0.5 volt difference between voltage measured across the battery (cranking) and starter to engine earth (cranking)

Edit: obv take all precautions with rotating parts

 

[GDSP]

What about cranking voltages?
Across battery without booster
Across battery with booster
And importantly battery positive to clean point on engine
And if you can get to it, main starter terminal to clean engine point.
All whilst cranking.
There should be no more than 0.5 volt difference between voltage measured across the battery (cranking) and starter to engine earth (cranking)

Edit: obv take all precautions with rotating parts

What about cranking voltages?
Across battery without booster
Across battery with booster
And importantly battery positive to clean point on engine
And if you can get to it, main starter terminal to clean engine point.
All whilst cranking.
There should be no more than 0.5 volt difference between voltage measured across the battery (cranking) and starter to engine earth (cranking)

Edit: obv take all precautions with rotating parts

Thanks , but now it's too late for more testing , I started to dismount everything to reach the injectors because when the engine starts and after let it running for almost 30m, the knocking sound doesn't goes away has does the smoke (a lot). I understand I'm going to need a special tool to remove the injectors, going to look for it at AliExpress

 

[carat 3.6]

Thanks , but now it's too late for more testing , I started to dismount everything to reach the injectors because when the engine starts and after let it running for almost 30m, the knocking sound doesn't goes away has does the smoke (a lot). I understand I'm going to need a special tool to remove the injectors, going to look for it at AliExpress

What color smoke?

 

[Smiley]

Have you checked the fuel filters Inc the smaller pre filter and it's o ring together with all of the fuel lines, air leaks are more common causes of starting problems than injectors. The air leaks are quite hard to find because the air gets sucked in rather than fuel leaking out. If the fuel lines look old, brittle and yellow then chances are the seals are ****ed.

 

[GDSP]

What color smoke?

Hello! Dark gray. The engine doesn't consumes a drop of oil

 

[carat 3.6]

Hello! Dark gray. The engine doesn't consumes a drop of oil

1. Remove and check each glowplug individually, use a battery and jump leads for that.

2. Check for corrosion on the fuse's, that type of fuse is known for bad connections even though they are not blown.

3. Check the catalytic converter isnt blocked, I had a e300D in recently with no power and a lot of gray smoke. Removing the cat cured that.