fixing fuel system on a 1983 240d

[why-is-my-username-taken]

I have a 1983 240d with 201,000 miles that hasn't been run in 3 months and am wondering if I need to clean the fuel tank and how I would go about doing that.

also, I will replace the fuel lines but can't seem to figure out which ones are high pressure and which ones are low pressure as well as how to relieve the pressure from them.
any and all advice is appreciated thanks.

[tangofox007]

Originally Posted by why-is-my-username-taken

also, I will replace the fuel lines but can't seem to figure out which ones are high pressure and which ones are low pressure as well as how to relieve the pressure from them.

The only high pressure lines are the ones from the injection pump to the injectors. There is no need to relieve pressure, especially in a vehicle that hasn't run for three months.

When you say "fuel lines," are you actually talking about fuel lines or just rubber hoses?

[BillGrissom]

3 months is nothing. A diesel can sit for 10 years and fuel not go bad, except if moisture gets inside the fuel tank to grow black slime. Boaters know about that, since damp on the coast and some engines are rarely used (sailboats). If slimed, you can pour in biocide to salvage the fuel (any truck stop).

If you do replace the rubber fuel hoses, best to use Goodyear "Barricade" brand, or equiv., which has a Viton liner and stamped "for bio-diesel". If like my 1984 300D, the return is a special swelled hose termed "cigarette". I thought it had swelled when I first saw one, but it's meant to be. Something about damping fuel system pulses, but probably not noticed if you use regular straight hose there. The max pressure on the rubber hoses is 12 psig, from the pressure relief on the injection pump inlet. It should decay quickly after shutdown, at least I've never seen a squirt when opening a hose after the Lift Pump.

[C.Doner]

Most recent postings that are void of all logic have been spammers. This one has a tone of that order. My suspect self says, it is either disgruntled banned's or other forums in competition. Otherwise, it does not make sense.

[why-is-my-username-taken]

Tangofox007 i am talking about the fuel lines not the rubber hoses

[why-is-my-username-taken]

Guys thanks for the reply’s I’m new here and still learning. About spam, no, me and my dad bought it as a project since we’ve never worked on diesels. To be more clear the motor starts and runs very easily but the fuel tank still hat the Diesel in it from when we bought the car 2 years ago. So I think I should have asked what i need to do about the old diesel.

[Diesel911]

Originally Posted by why-is-my-username-taken

Guys thanks for the reply’s I’m new here and still learning. About spam, no, me and my dad bought it as a project since we’ve never worked on diesels. To be more clear the motor starts and runs very easily but the fuel tank still hat the Diesel in it from when we bought the car 2 years ago. So I think I should have asked what i need to do about the old diesel.

There is a product called Startron for diesels that will kill anything in the tank and breaks up deposits. That can alleviate having to pull the fuel tank.

If here is a door back inside by the rear window for a first aid kit you can remove that and get at the fuel tank sending unit.


There are hoses and there are steel fuel lines.

If the steel fuel lines are OK there is need to replace them but make sure the rubber isolators on the clamps are functional or a hole can wear into the tubing. Another thing to look for is under the clamps the tubing tends to rust.

If for some reason you want to replace the tubing members have used Conifer brake tubing which is easy to bend without kinking, nylon tubing, and simply used fuel hose for diesels tided in place with zip ties.

There are likely other things used like aluminum tubing or copper (expensive).

If you buy new fuel tubing from Mercedes it comes somewhat rolled up and you have to unbend it.

The fuel outlet from the bottom of the fuel tank has a crimped-on collar. If need to replace that you should drain the tant and you file or grind of the collar metal meatal enough to get the collar off and get the hose off. After that you simply need another clamp and new section of hose to replace the collar.

To pull the fuel tank screen out of the tank you need a 47mm socket or?

[chasinthesun]

If it hasn’t been said already , 3 months is no problem if it had a clean tank to start with .Some tanks go south over a year sitting , pop the gas cap on some and yoll find rust forming in the neck , a concern over time . You can also peak down into the tank from above by pulling your sending unit , it’s under that tray on the rear deck behind the back seat , you’ll need a philips screw driver. Then a special larger socket to loosen the sender .

[vwnate1]

Take the time to learn about your car, once of the things it has is a clear plastic fuel intake screen before the fuel injection pump under the hood .

Wipe it clean and see if there's any crud in it ~ usually you'll fine some, occasionally the crud gets so bad the car runs poorly or stops running .

If it's running fine now, add some biocide (the crud in the clear intake screen is FUNGUS not Algae like some think) and then learn how to adjust the valves, they need adjusting every 10,000 miles or 12 months and no one ever does them so learn and do this A.S.A.P. .

WELCOME NEWBIE ! .

[nelstomlinson]

The diesel fuel is still fine after a few years sitting. Probably fine for decades, if it's dry. Diesel911 has some good advice about how to clean your system, but barring water in the tank, you don't have anything to worry about. I'd watch that clear prefilter for a while for signs of trouble, but you probably won't have trouble.

Biocide is good, and if you have algae it's necessary to use it, but be aware it will kill the algae and you'll have chunks of algae clogging your filters for a while. Biocide is good, but keeping your fuel dry is even better, because prevention beats cure.