well which would you go for. rebuild or new

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1971 280SE - The S Class
1974 280CE - Sterling
1988 300E - Stanley

I would never even think of a new or rebuilt pump if the old one was rebuildable.
Any decent Tinker Guy can easily tear one of these down and rebuild it. There is Probably a guy right near you.

That is what is cool about Vintage Benz parts..they are rebuildable, they still have rebuild kits , and the job is fairly simple.

But some guys just don't have a knack for rebuilding stuff...it is just second nature to me. And if I can't get the parts , I make them.

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A Dalton

Hi Arthur,

Ive spent the week thinking about my possibilities. And Ive got my result.

Ive decided to keep the old fuel pump, but not use it. Ill get a universal one to put straight into the line, and then send the return straight back to the petrol tank instead of into the pump and tank. This was what the bosch injection specialist in the capital city here reccomended I do. He said it would not only be far cheaper but practical considering its easy to obtain/replace/service.

If I ever find the seals Ill be sure to repair the old one. But untill then...

One thing I need to know is the PSI for the W108. I know its i litre in 15 seconds minimum. But I cant find the PSI reccomendations anywhere. How will I be sure to get the correct universal one. Im not quite sure on the info I need.

Cheers,
Luke

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1971 280SE - The S Class
1974 280CE - Sterling
1988 300E - Stanley

The pressure is also 15 max, but your problem is not pressure, it is volume.
That car has a Swirl Pot in the tank and it requires a retun line from the Injection pump in order to work correcly.
If there is no return, then you always have to have a 1/2 full tank for adequate flow.

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A Dalton

Ok, dont mean to be a pain but what is a Swirl Pot?? and will it be ok to simply put the return line into the tank and the intake line (IE put two T intersections and join them).

So this way the petrol is send from tank, to pump, to engine, then returned to the "tank-pump" line and to the tank aswell.

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1971 280SE - The S Class
1974 280CE - Sterling
1988 300E - Stanley

You just need a return line back to the tank from the Injection pumps back fitting.

The swirl pot is a little cup in the bottom of the tank that has no top, so if the gas tank is 1/2 full, the gas enters the pot from the top..BUT, if you get down below 1/4 tank, the pot needs the return line pressure to help keep the pot full.
The reason for the pot is so that when you are low on fuel [ less than 5 gal] , the feed line won't get air into the line as you corner or go up hills... the pot keeps about a guart of fuel at all times , regardless of the fuel tank level....MFI does not want any air in the fuel feed line, so they use the pot as a little fuel reservoir. And the return line is what keeps it full b/c of the venturi action of the return line pressure swirling in the pot. There is a small hole in the bottom of the pot, and the return swirl helps suck tank fuel into the pot thru that hole. W/O the return action, the hole would take too long to keep the pot reservoir full and the pot level would be the same as the tank level, but with that swirl action, the pot can stay full even when the tanks fuel level is LOWER than the pots level. It is a scavenging action that does this .
The screen that you access with the hex plug on the bottom of the tank is in the center of the swirl pot. And the feed to the MFI system comes thru the screen to the feed line.
Try Swirl or Flower pot in Search. There are some picture that make it very clear.
Here is one from 113 Group

http://www.sl113.org/forums/uploaded/ja17/200611475414_fuel%20tank%20with%20fp%20ill..JPG

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A Dalton