Fuel Injection pump

[1293]

Help - help, is there anyone who can help me? I have a MB 250 SL ( Pagode) year 1967, a American model. The car is wasting much oil, 1/2 - 3/4 liter of 20 km, the oil come from the "filter" on top of Fuel injection pump.
Oli pressure for the pump via the oli pipe coming from the engine and enters the back of the fuel injection pump, but there is no return connection for the oil.
There is oil sump and oil stick on the fuel injection pump.
I have owned and driven the car for more then 10 years without problems and suddenly one day there was a large oil leak.
The type of injection pump are: PES 6 KL 70A/120 R 18y.
I hope someone can help me, thank you in advance.

Greetings
Preben F.
   

[twistedtree]

On that pump there are two separate "zones" for oil.  At the rear where the internal weights and controls are located, there is an oil sump.  The oil in that zone is static and does not circulate with the engine oil.  You check the oil level via the dipstick, and fill and drain via the same hole which is tricky.

The other "zone" is the front part of the pump where the plungers are.  That is oiled from the engine feed line, and the oil flows back via a hole in the pump mount where it attached to the engine.

If the oil sump keeps filling up, it's coming from one of two paces.  The seals in the pump can start to leak and gas leaks into the sump causing it to fill up.  If this is happening the oil will smell of gas.  The other possibility is that other seals are leaking and the oil from the front zone is leaking into the rear zone where it has no way out.  If the oil does not smell of gas, then this is likely what's happening.

The solution in both cases is the same - send the pump out for a rebuild.  It may sound scary, but it's no big deal and you will be very happy with the results.  You could ship it to the US for rebuild (H&R Fuel Injection in NY is probably closest), but others can likely recommend a place in Europe somewhere.

[1293]

Help - help, is there anyone who can help me? I have a MB 250 SL ( Pagode) year 1967, a American model. The car is wasting much oil, 1/2 - 3/4 liter of 20 km, the oil come from the "filter" on top of Fuel injection pump.
Oli pressure for the pump via the oli pipe coming from the engine and enters the back of the fuel injection pump, but there is no return connection for the oil.
There is oil sump and oil stick on the fuel injection pump.
I have owned and driven the car for more then 10 years without problems and suddenly one day there was a large oil leak.
The type of injection pump are: PES 6 KL 70A/120 R 18y.
I hope someone can help me, thank you in advance.

Greetings
Preben F.
   

[1293]

Thanks for the reply. As far as I know, MB 250 SL had 2 different injection pumps, the latest models of the 250 SL has a hole where the oil can flow back to the engine, like the 280 SL, but the model I have, there is no hole or oil pipes for return , which I don`t not understand.

[Benz Dr.]

Some 250SL pumps have dip sticks and some don't. If you IP is designed for constant oil return, it won't have a dip stick becuse the oil level always stays the same. Once the oil level reaches a certain height it drains back into the engine through a drain hole.

If your IP doesn't have constant circulation, the oil coming from the high pressure line only lubricates the plungers. The oil also seals the plungers in a way that's similar to rings on a piston. This stystem uses a check valve in the high pressure oil line to prevent any fuel diluted oil from backing up into the oil galleys. This system must have this check valve to prevent fuel dilution at idle speed.
 
Normally, the engine oil pressure is high enough that the check valve is always open. It takes very little pressure to open this valve at maybe 6 lbs PSI. If you have a lot of engine wear and it's really hot day, oil pressure could drop below the point where this check valve will close. In this case, your IP will be getting no lubrication at the plungers. The IP can run for a while without any oil ging to it but it can also easily be damaged. If you find that your oil pressure gage is reading next to zero at idle, it would be a good idea to blip the throttle to increase oil pressure and keep the IP lubricated. The late style pump isn't affected in this way.

I've seen the odd check valve that was full of rust and not fuctional. This can lead to complete IP failure. You will need another pump at this point because your old one will only be good for parts. I would advise everyone to remove their check valve and test it to be sure it's working properly. It could save you a lot of money.

 

[1293]

Thanks for the detailed explanation. I know that on the MB 230 SL is a check valve on the oil pressure pipe, but where it sits on MB 250 SL, can it be inside the IP?
On my MB 250 SL that I have had for more then 10 years, there has been no check valve on the oil pressure pipe.
Thank you in advance.
Preben F.