T1N Black Smoke, nonstart, Loss of power


New member
I have an 03 T1N that has been putting out black smoke for about 2 months. The black smoke is not constant, but appears more often when accelerating uphill.

I have been losing power also. I can not find the pattern as to why. Normally I can just take my foot off and on the pedal a few times and will regain power. However, today I was unable to go over 30mph with my pedal to the metal. I’ll pulled off the highway and restarted the engine and when I pulled back on was able to get up to 70mph. When I did get past 30 mph a HUGE black cloud of smoke came out before it began driving normal again.

For about 1 month I have had issues starting the van. It’s happened about 15 times. The first time I was able to get it started by having a friend tap on my fuel filter with a hammer while I cranked the engine. This trick worked for about 5 or 6 more times until the hammer trick would not work anymore. I took the van into a shop that works on fleet sprinters. They replaced my fuel filter and cut one of the hoses coming from the filter that had holes/possible leaks around the rim. They charged me for an hour of diagnostics and told me that my starting the vehicle would no longer be an issue and that changing out the fuel filter resolved the black smoke issue as well. neither issues were resolved.

I also cleaned out my air filter and mass air flow sensor (lots of bugs in the screen that I couldn’t remove though)

I’ve checked for cracks in my turbo hoses (because of loss of power) but found nothing. There is however oil in the main turbo hose between the inter cooler and the engine attached with the spring clip.

Yesterday my van died while idling (for less than 3 minutes) and would not start back up. It was turning over just fine but no ignition. I saw bubbles in the clear plastic fuel line between the filter and the fuel pump attached to the engine.

My friend thinks it’s possible that the low pressure fuel pump in the fuel tank is malfunctioning and that the high pressure fuel pump may be trying to compensate. I was unable to listen for a hum from the fuel tank because when prepped to the engine started (quicker than normal) and it was hard to hear if the fuel pump in the tank was working or not.

Does anyone have any idea what could be causing the black smoke, loss of power, and sporadic nonstart issues? Are they connected?

I have had so much work done on this sprinter including having the transmission rebuilt a couple months ago. I am currently in Montana and plan to be in Washington, Oregon or, Idaho soon. Does anyone know of reputable mechanics that could help me get my van road worthy again because it’s hard going deep into the forests, not knowing if I’m going to be able to get back out and deep in the forests is where I’m trying to get back to!!

Thanks for reading,


UK 2004 T1N 313CDi
I have an 03 T1N ...

My friend thinks it’s possible that the low pressure fuel pump in the fuel tank is malfunctioning...

Thanks for reading,

First off your 2003 does not have an in-tank low pressure pump! The main engine mounted high pressure pump has to 'suck' the fuel up from the fuel tank.

The air bubbles you are seeing in the clear lines are not good and you will have to identify and correct the leak before going any further.



'05 Box Snow Camper

To get it fixed you really need someone who has worked through these types of vacuum issues in fuel systems. They can be difficult to work through. I was recently working on a 2003 which was getting air into the system and focused on all the usual suspects; the water in fuel fillter sensor mounting point at the bottom of the FF, the different o rings, the thermostatic valve, those stupid clips which break so easily, etc, etc. I even installed a small inline pump south of the FF but north of the tank. When installing the pump I finally found the culprit which was a very small spot where a hole had worn through the fuel line allowing air to get into the system.

Message is.. it can take time to figure out where the vacuum leak is occurring and you need to find someone who is willing to fully and completely look over the fuel system.

Also, if the problems have gottten worse since the other mechanic put on the new FF there’s a chance they didn’t install a good OEM FF.

Unfortunately, your black smoke is probably completely different from your non start issues.. whole other can of worms there. Check the air filter for clogging possibly injectors, there can be other reasons.

If your travels take you to Nor Cal feel free to get in contact.
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Former Nelson BC Sprinter
Air bubbles are the reason for a no-start & stall.
Most common cause of bubbles in fuel lines are poor seal /Oring connections to the fuel filter.
Disconnect fuel filter connections and lubricate Orings with thick oil or Vaseline and reconnect. Make sure water drain screw is lightly tightened as a child would, not forcefully tightened.
Or buy a fuel filter without a water sensor and drain screw if that doesn't work.
I can mail one to you if need be as I have left overs to sell, depending where you are.
More info in my signature line link

Black smoke may be from a leak in an old vacuum hose controlling Turbo actuator

In What Screen were the bugs ?
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Aqua Puttana

Poly - Thread Finder
Air bubbles are the reason for a no-start & stall.
Bubbles alone are normally enough, but there may be a combination of factors.

In What Screen were the bugs ?
Maybe an aftermarket MAF that has a screen. (Aftermarket MAF's are not always the best choice.)


I also cleaned out my air filter and mass air flow sensor (lots of bugs in the screen that I couldn’t remove though)

Unless the filter system is faulty, the MAF should stay white glove clean.

You really should replace the air filter. Cleaning may not be good enough if the media fibers are clogged. The dirty MAF points to a bad filter or air bypass one way or the other.

It may be worthwhile to visually inspect your turbo blades. The edges of the blades should be sharp with no rounded corners. If not clean and sharp the blades may be worn from dirt. Enough wear can reduce turbo performance.

:2cents: vic


Well-known member
I have posted repair techniques regarding these 2002/2003 NA T1N vans before, but I will post some important bullet points again.

With any diesel engine that has an engine mounted lift pump you MUST regard the whole system as TWO separate functioning parts.

1) EVERYTHING that is before the fuel the filter (including the tank)
2) All the rest of the FIE system including the filter.

Most problems are caused by careless installs/servicing, and /or overlooking some fundamental part of the system which avoids bubble free fuel flow.

The flexible fuel lines are specials with different ends formed/molded on them. Consequently DO NOT use aftermarket hose and hope they will clamp down and provide leak free sealing for the life of the hose--IT WON"T !
All too often the hose goes hard at the fuel pick up cartridge stub and allows air in --lots of it.
In short install only genuine MB hoses on the frame and use glemo style clamps to fit them.

Change them at 250,000 miles intervals because they go hard and crack !

Check the connections are correct!
All to often after having slithered under the rig, I find the suction line is fitted to the return.
I kid you not!

A simple mistake maybe, bit a real conundrum when on a road trip.

As with a situations like this use a dolly tank!
Again in short, take an empty gallon thinners can and cut a square hole in the top.
Dangle a 3/8" length of fuel hose in it and fill with diesel.
Sit in on the engine and connect the hose to the SUCTION side of the filter & let the frame/tank hose hang free.

Now fire it up and let the engine run on the dolly tank fuel.
No air bubbles! Then its pipes and tank etc so like Fido go sick-em!
Still aerating!
Then its going to be something with the filter . thermal valve or even excessive gases coming off the injectors
Again concentrate on that area not the upstream pipes & tank.

If you folks have ever worked on diesel stuff in the 1960/70's, with engine mounted lift pumps, air in the fuel problems were the norm. Big truck broken down with fuel problems were commonplace causing obstacles & road hazards . Traffic cop call outs were a frequent parts of a service shop and you had to know how to fix it fast on the A38 Cotswolds highway in my native Gloucestershire!
The many yurs later I am demo-ing a Cummins powered bus in Cleveland Ohio.
As an experimental bus Cummings Cleveland sent out a tech at 5,00 am on a bitter cold morning to check on cold starting & priming.
Once out the cab he reaches for --YES --A dolly tank just the same as I used ont'other side of the pond. This Africa American Clevelander might have had a different accent than me--BUT he "spoka my universal how to fix/check it language!":thumbup:

Use a dolly tank when having fuel trouble--Its what the Pro's use!
Yes even the professional mechanic African Americans bless 'em!
All the best


'02 2.7 T!N Freightliner
This is exactly why I was able to buy a 2002 Sprinter van for $300.
The owner wanted it gone.

The repair records showed three separate attempts to install fuel filters trying to get the hot starting problem fixed.

One garage in desperation did a $2000 brake line replacement.
The bubbles in the clear plastic line from the fuel filter to the low pressure pump were beautiful.

And I was ignorant but I learned the basics fast.

What a crazy strange wonderful trip this Mercedes diesel engine is.
It would have been easier to learn Chinese.

bill in tomahawk
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New member
Update: the engine died while idling for 20 seconds yesterday. It would not start back up. I left it alone for 1 hr and it started up with no issue! Any insight on why the engine cooling down would make a difference ?

Aqua Puttana

Poly - Thread Finder
... Any insight on why the engine cooling down would make a difference ?
Some electronic circuits/sensors can be temperature sensitive in the early stages of failure. Electrical connections can also be temperature sensitive.

You probably want to know which one. :idunno: There are too many possibilities. Troubleshooting will be needed.

:cheers: vic


'05 Box Snow Camper
Wonder if the thermostatic valve on top of the fuel filter might be letting some air in once the fuel is warm/hot?

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