W164 ML320 CDI engine issues - new mechanic?

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b0gd4n

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Jan 8, 2012
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9
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ML320 (W164)
Hey there,

I have had my 06 ML320 CDI for about 2-3 years now and for the past 4-5 months, it has started showing some signs of old age (105,000 miles).


1. First of all, the engine start up. Every morning it takes quite some time to get the it started, varying between 5-10 and sometimes even 15 seconds. Once started, it's fine throughout the day. If I leave the car off for a few days, it get slightly worse, starting even harder.

My mechanic told me that it might be related to the fact that not all the injectors are working properly. However, lately, I have started to lose trust in my mechanic (had the turbo reconditioned about 1 year ago and last time I took the car to service, he charged another £200 or so on some more turbo work, telling me that it was not working properly....hmmm).

Back to the problem at hand, I started asking around, and was told that the start-up problem might not have anything to do with the injectors, (as the ones that are working fine, should compensate for the ones that are not) and in fact be that the fuel system is losing pressure somewhere. I sense that the latter opinion is much less costly.


2. Secondly, after starting the car, leaving it on idle for 5-10 minutes it start spewing smoke out of the exhaust. Throttling does not help, the smoke keeps coming, even during driving.
Again, asking the mechanic's opinion, he told me that this could also be related to the injectors. For the same reason mentioned above, I started asking some friends about it and found out that (as before) it might not have anything to do with the injectors, but with the EGR valve not being cleaned.

I would very much appreciate some of your opinions on these 2 matters.
I am actively searching for a better mechanic that will not dry my wallet (in London).

PS: one other thing, not related to engine issues though, is that the parking brake handle now sticks out. I can pull the brake, but I need to push the handle back into place. Is there a way to tighten the brake cable to keep the handle back in place?
 
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Try to leave your car with a full tank (to the brim) over night, or park your car with the front on higher level just to eliminate any problems with air in the fuel lines. If it starts like before you should check the 'o' rings on the fuel lines and pumps.
 
Try to leave your car with a full tank (to the brim) over night, or park your car with the front on higher level just to eliminate any problems with air in the fuel lines. If it starts like before you should check the 'o' rings on the fuel lines and pumps.

thank you for the suggestion.
will try that and let you know.
 
You might want to try leaving the car with the back, not the front on higher level to stop the fuel going back to the tank. My mistake.
 
A very slight hole in one of the fuel lines, on the LOW pressure side (pre pump) could allow small amounts of air to enter the system, needing extra cranking to "bleed" the system through before proper amounts of fuel are available to start cleanly. Do you get any diesel fuel odor from the car when you walk up to it in the mornings? Morning Clatter's suggestion might help identify this.

Secondly, is your battery good? A poor battery is more likely to lose charge on the days you don't use the car - especially in colder weather - meaning longer cranking times. Additionally, if battery voltage is low, it can affect the injector cycling causing other issues. I've changed batteries on a car and right away seen it run better. The flip side of this is of course how efficiently is your alternator working in this cold weather? Are you generally doing short-ish trips or does the car get a good run each time you use it?

EGR is another good thing to check, they can stick open or closed, usually if they stick closed the car runs better, but may trip a CEL and cause limp mode, depending on the car and age. If stuck open this would most likely mean starting ok, but losing power and seeing excessive black smoke when driving. Well worth checking the EGR for crud build up periodically regardless - the one on my 5 year old focus was a MESS, like someone had poured black treacle in it.

Injectors can cause problems, your mechanic isn't wrong there, however he should certainly consider other (cheaper) things first. Injectors issues could be linked to another fault (battery/power) and not the injectors themselves, so changing them would have no effect.

Fuel pump is another good one, modern diesel run at 15,000 psi+ this pressure is needed to ensure both that the right amount of fuel is delivered (injector is open for a programmed amount of time) as well as ensuring a good, even spray pattern.

Glow plugs: have you noticed if the glow plug light is staying on any longer in this weather? They should stay on as long as they need (usually no more than a second in my experience) but they still might not be doing a good enough job, making that initial start harder. What you can try, if your glow plugs are a little "weak" it do turn the ignition ON, wait for the light to go out (if you even notice it, it may be really quick) then turn the ignition OFF again and repeat a couple of times before finally cranking the car. If it then starts cleanly from cold, this is a sign that maybe the glow plugs are indeed weak and needed a couple of additional attempts to provide the heat required for a clean start in cold weather.

I also had an issue with a solenoid causing me problems. A variable vane turbo, when at idle will have the vanes closed to allow for boost at low rpm. As rpm / load builds these open to bleed off exhaust gasses to maintain the boost level - not unlike a waste gate in some regards. One of my cars had a fault whereby - due to a broken solenoid - the turbo was stuck in the high-rpm/load position meaning it was gutless at low rpm, but fine by 2,500 rpm and a screamer by 4,000rpm. When I sorted this the car seemed to start more easily (exhaust gasses were not being bled off) and the low-down torque become fantastic - the thing used to stall all the time & I'd have black smoke out the back as it was fueling for a high boost situation, but was getting no boost. Basically it over-fuelled hence the black smoke.

I've experienced all these issues on Diesels (I owned a Ford, learnt so much about fixing sh1t like this lol)

Likely more things that might cause your issues, but my brain is full of stinking cold currently, so it's only running on three cylinders :)

Scoob.
 
thanks all for the suggestions.

leaving an update on the situation. done the following:

- I have changed the fuel filter, which was extremely dirty.
- I cleaned the EGR valve, again dirty.
- I replaced the turbo breather gasket, as my brilliant mechanic tore it apart when he mounted the turbo back on (after the second time he claimed it needed a refurbishment...)

Now, I have no smoke problems whatsoever.
However, the starting problems persist. I still have not tried out some of the suggestions above, so need to do that. Am also planning on going to another mechanic (some of my friends seem very happy with him) and see what is the outcome.

Will keep you posted.
 
It is very likely to be caused by a faulty glow plug control unit. Very common issue.
 
Fuel system/air leaks on this car is very rare indeed.
 
I have the same engine as you, and had similar starting problems.

Turned out that, like you, I had a very dirty fuel filter. This was causing partial vacuum probs, as it was causing air to be sucked into the lines between the filter housing engine side, and the rail.

May be worth checking/replacing the seals in this area in case suction's shot one or more while you had the dirty filter.
 
This morning, before starting the car, I left the ignition on for about 10-12 seconds, turned it off, for about 10 sec, back on for about 10, off, for then and then started.
The car started better than usual.
 
+1, common issue that I also had on my ML320. New module is a DIY fit for just £135 from an MB dealer.

yeah, gonna go next saturday to a good (reputable at least) service. will let you guys know what it turns out to be.
 
as above, and also check the o -rings on the pressure regulator at the back of the rail, its worth changing them anyway at 8 quid for the kit.

edit just saw its a 320 so may be ok on the o rings
 
I took my car to the mechanic and he changed the glow plug replay and now the car starts like it was new. This turned out to be quite a cheap fix! Very happy with it now.
About the idle smoke, he mentioned it was related to the injectors. However, this would be quite the expensive fix. Leaving this for a bit later on.
 

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