Just picked up an 8 deuce SD. Car is in good shape but still needs a little TLC. Somebody did a botched veggie conversion on this car. Long story short, they jumped ship and tried to get it back to stock after failing miserably. It was running like a champ before it was "worked on" but after replacing the fuel tank that had been drilled into and hooking up all the lines back to stock the car now sucks air into the fuel. I know what everybody is going to say, it's a bad fuel line or loose clamp. Well here is the kicker...The car was fitted with a plastic 5 gallon diesel purge tank in the trunk. This is basically a normal plastic fuel can with a supply and return fuel line added. When the small 5 gallon tank is hooked up the car will run all day as long as there is fuel in this tank. When the stock tank is hooked back up some air is getting in. It also did this with the stock tank that was butchered after the guy tried to do a veggie conversion.

I have gone over this car a bunch of times and have checked every hose and clamp and they are all tight. And the banjo bolt is as clean as a whistle. Any ideas?

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1985 Mercedes 300DT

Is the origional fuel tanks vent still functioning (drive car without fuel cap to see if it improves)? Is the origional fuel tank screen pluged up?

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84 300D, 82 Volvo 244Gl Diesel

Sounds like you may have the suction line hooked up to the vent tube. Make sure the supply line is connected to the tank screen (46mm nut looking thing) nipple and not one of the plain nipples.

Sorry it took me so long to answer back on this one....

Anyway, I have hooked up all the supply and return lines in every configuration I can imagine and the car still runs like crap on the stock tank no matter what. But when I hook it back up to the 5 gallon jug it runs like a champ...This is mind boggling to me.

Just to make sure...which one is the supply line in the engine compartment? It's the one that runs straight to the filter. These lines were also re-routed and the un-rerouted when the guy tried to turn it back to stock.

Does anybody have a diagram that they can post for me...I want to make sure all fuel hoses are in their correct place.

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1985 Mercedes 300DT

No the top line is the return. The supply line is the lower of the two, going to the primer.
Sounds like you do have an air leak somewhere, if that five gallon jug, wherever is it located, runs fine.
Good luck.

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83 SD

84 CD

I do have an air leak somewhere, but where is the $64 question.

Like I said, the car ran fine on the original stock tank. Then after the botched veggie attempt the car was put back to "original" and started to suck air. Then the original stock tank was switched out for another tank, hooked up and the problem persisted with another tank. If you take the same lines that go to the stock tank and reroute them to the 5 gallon jug in the trunk the car runs great.

Diagram anyone?

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1985 Mercedes 300DT

Okay, I think I am on to something here...Yesterday I took a good look at the fuel hoses under the hood and it looks like the guy hooked the supply line straight to the filter, then the line that goes out of the filter (where the out arrow is) hooks into the line that is on the right of the plastic manual pump, then the line that goes out to the left of the plastic pump is looped to the IP. This doesn't make sense to me...Can somebody give me a quick explanation on the correct configuration of the fuel lines..

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1985 Mercedes 300DT