W111 250SE Coupe Injector Pump Issues

[RichardGP]

My new to me 66 250SE W111 coupe has a pretty bad oil leak around the red "oel" cap of the fuel injector pump. It's fresh engine oil which is supplied to the pump via a feed from the main engine. Can you help with any suggestions?

Is the oil in that part of the pump designed to be pressurized? (i.e. should the cap be able to seal against the pressure? I don't see any gasket around it)
If it's not meant to be under pressure, what could that mean about the pump?
Any suggestions from anyone regarding a repair facility for these older models in Michigan?
If I have to get the pump pulled off and sent for service, suggestions on a good source to do that?
Thanks for your help!

Richard

1966 250SE Coupe
1957 220S

[wwheeler]

Because you have the oil cap, that means you have an early pump and the rear has its own oil supply. The later models do not have that. The rear section is not fed by the engine oil. Engine oil is fed into the pump but only the front part. I forget exactly was is the cause for the rear to fill up with oil, but  there are many posts about this. Search for them. Also look in the tech section for information about the different pumps. More than likely, a rebuild may be in order.

[dirkbalter]

Also, do you have the correct amount of oil in the pump? (Not overfilled?)
There is dipstick you can unscrew and verify.

[RichardGP]

Hello, thank you all for the helpful comments. Mine is the 'non-dipstick' style pump. The rear part of the pump is receiving a flow of continous, fresh, engine oil (with no fuel in it) coming through into to the rear section. It flows quite continously...about one drop every 5 seconds and a stream coming out from under the red breather 'oel' cap. I haven't taken the pump off yet to see if it has the drain return in the front section near the spline, but either way the oil should not be in the back section and under pressure? Suggestions I have received so far are that:
A) This is not normal for the rear part of the pump to experience oil pressure
B) Probably the seals around the lower parts of the front section are leaking or damaged
C) The pump will need to be repaired - H&R Fuel Injection or Jerry Fairchild were two suggestions. Any others?
Thanks all!

Richard.

[wwheeler]

I may be wrong, but if the pump is fed engine oil throughout the pump, what is the purpose of the red OEL filler cap? My 280SE doesn't have that and is for sure the later full feed type pump. I have a 220SE that is earlier and has the oil cap and dipstick. Are you sure you don't have the dipstick? The tech manual sows an example of this dipstick.

[dirkbalter]

Not complete sure either, this is my 250 / R18 pump with dipstick.

[Benz Dr.]

This car should have a dip stick on the IP. It's not normal for oil to be coming out of the fill port so I'd say the seals are leaking inside of the pump. Oil level should NOT increase or you have problems.

[RichardGP]

You all are correct, if it has the "oel" cap it is the older style with a separate oil reservoir.

So I found the dipstick, took it out and of course there was plenty of oil overflowing. Waited for it to clear, put it back in.
Started engine to see if oil level increase up to breather cap, nothing yet. The oil that came out seems like pretty clean engine oil, no fuel I can see but maybe the very slightest odor.

Pump ID plate shows model PES 6KI 70A120 R18 which confirms older style I believe. The quantity of oil in the photo is what came out from about 10 minutes engine run time at idle plus what drained out once I located the dipstick.

Looks like the pump is going to need some attention....
Thank you everyone! You Pagoda guys are the best. My BAT dream car has left me with a hangover on its first day, but we'll get it sorted. Now after two days I have a sense of where this headed.

[BlackForest]

Hi Richard,

All 250SE/SL motors have the R18/Z/Y pumps which all have the separate oil supply and dipstick.
The reason your pump is filling up with oil is from a failure of the oil block seals at the base of the plunger and barrel assemblies.
Replacing those requires a complete rebuild of the pump.

My shop is located in Milwaukee WI and we can rebuild the pump for you.
Please give me a call to discuss if you are interested and would like more info on this.

www.blackforestllc.com

Michael
414-228-4899

[Alex D]

Michael at Blackforest rebuild by 250sl R18 injection pump back in 2016, no problems. Know's what he's doing.  Would recommend.

Alex D

[RichardGP]

Thanks for the great recommendations guys. The plan is coming together to address the pump seals. Thanks!