ML320 55 plate

[Ashley1090]

Hi all,

Im after some help and advise, my ML has became poorly, it seem to loose power after a certain amount of driving (40 miles), i have recently changed the plugs, gasket rings and a brand new battery. I know that the next thing is probably the alternator however the merc specialist who looks after my car said it could be 101 things however due to lock down etc he cant look at it at the moment.
I have never used a forum before but i know that most of you guys really know your stuff so would any of you have any suggestions that i could try myself to get my car running again.
Its my pride and joy and also my family car for the kids, im self employed and not working at the mo because of lock down so i am looking for something i can try myself at home at a low ish cost if possible.
Thank you for reading and i look forward to your responses ,
Many Thanks


Just to update its a mercedes sport ML320 3.0L DIESEL
ALSO JUST TO BE CLEAR IT IS ELECTRICAL POWER I AM LOOSING

 

[ajlsl600]

no warnings displayed ? if not you really ought to get it on a decent code reader/star diagnostics, you can really wreck yr wallet guessing. its not misfiring ? ,right where are you ? as u say lock down and most with sense not taking travel risks . i use clone of mb star ,but someone will recommend something that maybe amazon can deliver loads on here can help if you get a fault code .

 

[John Laidlaw]

As your man says it could be a number of reasons , sadly a decent diagnostic which you can’t get right now is the best chance of narrowing it down
Injectors , blocked fuel filter, poor or old filters (air etc), MAF defective, glow plug relay ( although starting problems might be present too) - list goes on.
When did it last have a service ?
If a long time ago it could be worth doing yourself ( not injectors though)
If you have £150 ish spare to spend the icarsoft MB 2 diagnostic tool could help( buy from UK Tools direct) if you can get one during lock down

 

[John Laidlaw]

Sorry - is it a cdi or petrol ? Just noted you’d changed ‘plugs’

 

[Wighty]

If it’s the om642 diesel you could try the resistor fix for the inlet port shut off motor . A 4.7k ohm resistor into the middle two terminals of the motor (below the black batwing air intake for the turbo )
Might cost 20p and under an hour diy

 

[LostKiwi]

Sorry - is it a cdi or petrol ? Just noted you’d changed ‘plugs’

Yep I noticed that too - if petrol ignore Wighty as his information is for a diesel.

If petrol you could try disconnecting the MAF once it's misbehaving and see if the fault changes. Be warned it could put the engine management light on but once reconnected should go out fairly quickly. The advice to get an iCarsoft is good too - it will let you read the codes yourself. Don't be tempted into a generic code reader as it won't read your car properly.

 

[Ashley1090]

no warnings displayed ? if not you really ought to get it on a decent code reader/star diagnostics, you can really wreck yr wallet guessing. its not misfiring ? ,right where are you ? as u say lock down and most with sense not taking travel risks . i use clone of mb star ,but someone will recommend something that maybe amazon can deliver loads on here can help if you get a fault code .

Thank you for your response, no there are no faults (until bat starts to die then its a christmas tree), when car is running on a charge it runs fine, i am in bordon hampshire

 

[Ashley1090]

As your man says it could be a number of reasons , sadly a decent diagnostic which you can’t get right now is the best chance of narrowing it down
Injectors , blocked fuel filter, poor or old filters (air etc), MAF defective, glow plug relay ( although starting problems might be present too) - list goes on.
When did it last have a service ?
If a long time ago it could be worth doing yourself ( not injectors though)
If you have £150 ish spare to spend the icarsoft MB 2 diagnostic tool could help( buy from UK Tools direct) if you can get one during lock down

had a service about a year ago, hasnt done many miles since last one to be fair, i changed all glow plugs the other day but had the power issue before the change

 

[Ashley1090]

Yep I noticed that too - if petrol ignore Wighty as his information is for a diesel.

If petrol you could try disconnecting the MAF once it's misbehaving and see if the fault changes. Be warned it could put the engine management light on but once reconnected should go out fairly quickly. The advice to get an iCarsoft is good too - it will let you read the codes yourself. Don't be tempted into a generic code reader as it won't read your car properly.

ITS A DIESEL 3.0L X

 

[ajlsl600]

ITS A DIESEL 3.0L X

"changing the plugs" a little misleading , however if you can go down the code reader route . most likely will lead you to solution ..unfortunately modern cars make this a necessity..

 

[Wighty]

Yep I noticed that too - ignore Wighty as his information is usually ????
.

Fixed it for you buddy

 

[LostKiwi]

ITS A DIESEL 3.0L X

I hear ya!

 

[John Laidlaw]

So your edit says it’s electrical power you are losing- that makes a big difference to the likely responses...

 

[CrustyClam]

Are you having to recharge your battery with an external charger?

What exactly do you mean by loses electrical power? What do you experience?

Can you stick a multimeter over the battery terminals and see what the voltage shows when you have the issue with the engine still running?

Rear Sams can cause electrical issues if damp/wet, that area leaks, but it wouldn't just appear just at 40miles