pictures? Sounds interesting.

 

http://www.benzworld.org/gallery/data/500/medium/P1170309.JPG

 

This is obviously not the place for 508 owners - so if you are someone like me looking for like minded people for help and support go here instead...

https://www.facebook.com/groups/26567283036/10152307749848037/?notif_t=like

 

Hi - I have a 1984 mercedez 508D converted campervan. I've had it now for 1 year and in the last few months have experienced a number of issues - I am based in the Algarve & it's been to a number of mechanics who 'fix' the issue but i've broken down a number of times. Had a new starter motor, alternator, diesel filters & tubing but yet when I drive for around 40 minutes the engine cuts out and it starts to chug. I've taken it to different people who have told me there was a lose connection somewhere, filters needed changing & 1 removed as I had 3. But the problem persists and now i've been advised that it could diesel fungi in the tank Has anyone had this issue and can please provide me with some advice as i'm so overwhelmed & have paid hundreds of euros and yet am still breaking down. Any help is greatly appreciated

 

Diesel fuel grows algae, and there are fuel treatments (here in the US) that prevent it. A typical situation is that there is a screen in the vehicle fuel tank, which gets coated with a mucky layer of algae, or that there is an amount of algae and/or other debris in the fuel tank that get's suck against the fuel outlet(screen) during driving. Then, once the vehicle is shut off, and there's no more suction being applied, all the debris or algae fall away. The engine can be restarted, and driven, and then at a certain amount of driving time, the process repeats. It's not uncommon, and gasoline powered vehicles can have the same situation. When I purchased my Coupe in April '92, the seller was getting rid of it because of this issue, and because none of the shops he'd taken it to (in the San Francisco Bay Area) could fix it. The car would run for 30min, die and not restart. Get towed to a repair shop. Sit there waiting to be worked on, and then restart and run fine, as if nothing had happened. I found the screen in the electric fuel pump intake pipe was packed with a 1/2"/13mm thick plug of grit from the fuel tank. It was so packed in that I had to dig it out with a screw driver blade, and then blast the fitting out with compressed air. I've never had a problem since.

Knowing that your campervan has a repeating history, if I were working on it, I'd look to see if there was a pre-filter screen in the fuel tank, and I'd check the fuel tank for debris/rust/water in the bottom of the tank. Depending on what I found, I would move forward through the fuel system, checking for pour fuel flow, and blowing through fuel hoses and pipes in both directions with compressed air (after removing them from whatever they were connected to). I would continue with the "confirm excellent fuel flow" diagnostics, until I had excellent flow right up to the mechanical injection pump AND from the injection pump, returning to the fuel tank. If there's vent in the fuel tank, and/or in the fuel cap, I would also confirm that hose had excellent flow.

It's not rocket science.

 

1984. I’m guessing that’s an om617. Is that correct?

The worry about taking it to lots of mechanics is that they might not be documenting everything they are messing with.

Owning an old vehicle, it is smart to be handy and learn how to fix them yourself as well as possible, and diagnose the problems on your own.

Diesel Fungi doesn’t sound like a diagnosis, more like a lack of diagnosis. Diesels usually aren’t really happy until they are warm. Sure, maybe the fuel filter is getting clogged and it’s not getting fuel to the injector pump for some reason, but diesel fungi is not a diagnosis. That sounds like what a mechanic will say when they are giving up.

The w123 and w126 sections will probably have the same motor (after you identify yours), and peachparts is also another site that is pretty big into the diesel MB stuff. If you need direction to those forums, let us know.

 

The concept of a clogged fuel filter is common in all old vehicles, not just diesels (probably more common in gasoline vehicles where the fuel turns to varnish). But Algae doesn’t grow anywhere there is no sunlight. I have no idea why people call it algae. Addressing "Algae" in Diesel Fuel

 

The concept of a clogged fuel filter is common in all old vehicles, not just diesels (probably more common in gasoline vehicles where the fuel turns to varnish). But Algae doesn’t grow anywhere there is no sunlight. I have no idea why people call it algae. Addressing "Algae" in Diesel Fuel

I call it black s**t. It clings to tank strainer and starves lift pump. Once it develops it is very difficult to get rid off. Campers and boats are worse offenders because of seasonal use.

 

@Fayeward
Without more vehicle details like VIN or FIN it is difficult to determine which fuel supply system it has. There are dozens if combinations. Fuel tank in the back, on the left side, right side, dual tanks, triple tanks.

Most likely engine OM314 has lift pump that sucks fuel from tank through strainer and feeds injection pump through fuel filters. That pump is not very powerful. Any restriction or tiny air leak will starve engine to death.
You need to find a shop where head mechanic walks with the cane.