Fuel pump 350SL

Hello, I have decided to change some fuel parts. After disassembling fuel pump I found a spring and a little ball in the hose which goes from fuel filter. The spring seems to be half way out, a photo attached. I guess this is not normal, isn't it? Can it be fixed somehow? The pump has been working before disassembling. 
Thanks&regards,

Dodi
350SL '72
 

Hi,
you found parts of the valve that hinders fuel-flow-back, the non-return-check-valve that is part of the pump.
Now - the valve is not functional anymore - fuel pressure gets lost very fast after engine-shut-off.

You could replace the valve by an external one, like this <just an example> www.ebay.de/itm/353539487622?hash=item52...6:g:WNEAAOSwRldgzIVC

Regards
Norbert

Hello, thank you for your reply.
Could you please give me more information on this. The pump was working before taking out of the car, at least I think because I had no issue with the car. How could this happen?

In order to replace the valve, do I have to take out the spring and the ball from the pump and after connect a new valve?
Thanks.

Dodi

Hi Dodi,

inside the flange of the pump there is a mechanical limiter for spring and ball. When this breaks, ball and spring flow out and no longer work as retain valve. That means that pump will still work but pressure in ring line in engine will drop immediately after shut-off of engine. That means that starting engine will take longer as ring line needs to be refilled with fuel first.

As we do not have new retain valves available, we use an external valve instead.

I just took a closer look on the pump. There is a hexagon nut on the non return check valve so plese ignore ma second question. The nut seems to be difficult to remove, in worst case scenario it might brake, so I am thinking of buying a new pump, taking into account age of the old one. Could you recommend any available for a D jetronic?

Thanks&regards,

Dodi

Hi,

best solution is to keep old pump and install a non-return valve.

Hello Volker,

thank you. So I will not even try to remove the nut. I just found these items:

www.ebay.de/itm/324365729021?fits=Platfo...SwJzpg2r2o#vi-ilComp

www.ebay.de/itm/294269892457?fits=Platfo...9:g:fUoAAOSwQkVg3PbP

The first one is home made and the second one from chasis no. 012224, my chasis is 007668 although engine and year match.

What do you think?

Thanks a lot & regards,

Dodi

I wrote already what I think: jetronic.org/en/d-jetronic/fuel-pump

Hello Volker,

thanks, I will follow your advise and install a new return valve. Can I insert it just after the fuel filter(closer to engine) or it has to be between the pump and filter?

I also plan to replace the injector nozzle hoses. Are they a common fuel hoses which I cut to specified lenght or do I need original MB parts?

Thanks&regards,

Dodi

Hi Dodi,

it does not matter as long as your filter does not leak. Any fule hose will do. But do not use the ones with textile outside. They are bad quality nowadays. Take one with different rubbers inside NBR and CR (UV resistent) outside and a textile stengthening between them.

Thanks Volker.
The things gets more complicated than I thought. I was just checking the fuel lines and after cleaning them a bit I discovered they are quite rusty. The best would be to replace all fuel(and brake) metal pipes. I guess that a rear axle has to removed and maybe an exhaust as well? I did not notice any connections, is it possible that the pipes are in one piece from the front to the rear end?
The worst part is the main feed fuel pipe from the last rubber holder to the tank. Does anybody have experiences with this kind of job on the back from the garage floor?

Thanks,
Dodi

Hi Dodi,
No axle has to be removed for this.
greetings Hans-Jürgen