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  #1  
Old 10-10-2021, 08:24 PM
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W115 240D injection pump oil leak.

Hi all. I am leaking oil from the fuel shut off control arm. Does anyone have a solution to fix this problem. I loose about 2 table spoons just sitting over night after driving 24 miles from work.

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Old 10-11-2021, 11:38 PM
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What I am finding interesting is that on a 1976 W115 240D your oil level should not be high enough to leak out of that area. There is only supposed to be like 1.5 inches of oil at the bottom of the pump regulated by the oil drain tube on the engine side of the fuel injection pump.

That being said there is an O-ring in there some where that replacing may help.
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Old 10-11-2021, 11:46 PM
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Excess oil is supposed to drip out of the red circled area tube. You dump the lube oil in and as over time fuel leaks buy the Element/Plungers and barrels diluting the oil and causing it to leak out of the tube.

You are supposed to take something like a turkey baster with a tube on it and suck out the contaminated oil once in a while and fill it with new oil.

In the 1970's they put 40Wt oil in those pumps.

If your oil level is high remove that tube and clean out the banjo bolt. If for some reason there is a plug there remove the plug and drain out the oil and refill with oil till it starts draining out and replace the plug. If you have a plug every so often you need to remove the plug and drain out the mix of fuel and Oil. It is up to you when to such out the fuel/oil mix and again replace it with only oil.
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W115 240D injection pump oil leak.-197-240d-fuel-injection-pump.jpg  
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Old 10-12-2021, 12:21 PM
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Quote:
Originally Posted by Jbyron View Post
Hi all. I am leaking oil from the fuel shut off control arm. Does anyone have a solution to fix this problem. I loose about 2 table spoons just sitting over night after driving 24 miles from work.
Two tablespoons of fluid on the ground after driving the car sounds like a lot. Assuming this is coming from the injection pump (IP), I'd say this is more than a tolerable leak.

There is no engine oil feed to the injection pump like there is on later engines, so there's only so much oil that could leak out before it's dry. If your car's IP is leaking a significant amount of fluid while running, then it's likely to be fuel rather than oil (or a mix of the two until the oil dilutes out and only fuel is left).

Fuel could leak into the IP's sump past worn injection elements. Some of this leaking is normal, and is why we must change the IP's oil at intervals. I do mine when I change the motor oil, and I use the same oil to fill. If the elements were worn enough to leak as much fluid as you are observing I'd guess that the engine was not running all that well.

Fuel could also leak into the IP's sump from the lift pump. I had this problem with the '74, which came down to a bad O-ring on the push rod that operates the lift pump. My car's symptom was excessive fuel coming from the drain pipe on the engine side (visible in Diesel911's post above). I corrected this problem when I rebuilt the lift pump. I still get some fuel in the oil, but not enough to cause it to drain from the pipe between oil changes.

Here's what the push rod and o-ring look like:


That photo is from this thread:
http://www.peachparts.com/shopforum/vintage-mercedes-forum/368673-w115-220d-240d-lift-pump-valve-rebuild-kit.html#post3674612

When changing the IP's oil you can't drain all the fluid out; there isn't a plug low enough. The idea of sucking it out with a baster or other tool is intriguing but I've never tried it. IIRC the book says to open the drain plug (see next paragraph) and pour fresh oil into the IP until the fluid coming out is mostly oil. The oil is more thinned with fuel when you first start pouring.

Here is a photo showing the LH side of one of these IPs. You can see the mount for the lift pump, pump removed. Then to the right of that is another hole which is where the drain plug threads in (plug not present). It's a hollow bolt for a banjo type fitting, so you don't have to remove it from the hole for it to drain. It's got a 14mm head.



Oil coming from the shut-off lever's shaft indicates a bad o-ring there. Also, if the drain pipe on the other side is adjusted high, the fluid level could be coming up to the shut-off shaft before it makes it up to the drain pipe.

In your shoes I'd open up the IP's drain plug, let the excess fluid out, and flush with fresh oil. After flushing with fresh oil close the plug and don't add more oil. Then run it and see how long it takes for it to start leaking again. And check that drain pipe per Diesel911's suggestion to make sure it's clear. If it starts leaking again soon after then you will be looking for the source, and if the car runs well chances are the excess fluid isn't coming from the elements. That would finger the lift pump as the primary culprit.

Hope this helps!
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Last edited by gmog220d; 10-12-2021 at 12:46 PM.
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Old 10-12-2021, 04:53 PM
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Quote:
Originally Posted by gmog220d View Post
Two tablespoons of fluid on the ground after driving the car sounds like a lot. Assuming this is coming from the injection pump (IP), I'd say this is more than a tolerable leak.

There is no engine oil feed to the injection pump like there is on later engines, so there's only so much oil that could leak out before it's dry. If your car's IP is leaking a significant amount of fluid while running, then it's likely to be fuel rather than oil (or a mix of the two until the oil dilutes out and only fuel is left).

Fuel could leak into the IP's sump past worn injection elements. Some of this leaking is normal, and is why we must change the IP's oil at intervals. I do mine when I change the motor oil, and I use the same oil to fill. If the elements were worn enough to leak as much fluid as you are observing I'd guess that the engine was not running all that well.

Fuel could also leak into the IP's sump from the lift pump. I had this problem with the '74, which came down to a bad O-ring on the push rod that operates the lift pump. My car's symptom was excessive fuel coming from the drain pipe on the engine side (visible in Diesel911's post above). I corrected this problem when I rebuilt the lift pump. I still get some fuel in the oil, but not enough to cause it to drain from the pipe between oil changes.

Here's what the push rod and o-ring look like:


That photo is from this thread:
http://www.peachparts.com/shopforum/vintage-mercedes-forum/368673-w115-220d-240d-lift-pump-valve-rebuild-kit.html#post3674612

When changing the IP's oil you can't drain all the fluid out; there isn't a plug low enough. The idea of sucking it out with a baster or other tool is intriguing but I've never tried it. IIRC the book says to open the drain plug (see next paragraph) and pour fresh oil into the IP until the fluid coming out is mostly oil. The oil is more thinned with fuel when you first start pouring.

Here is a photo showing the LH side of one of these IPs. You can see the mount for the lift pump, pump removed. Then to the right of that is another hole which is where the drain plug threads in (plug not present). It's a hollow bolt for a banjo type fitting, so you don't have to remove it from the hole for it to drain. It's got a 14mm head.



Oil coming from the shut-off lever's shaft indicates a bad o-ring there. Also, if the drain pipe on the other side is adjusted high, the fluid level could be coming up to the shut-off shaft before it makes it up to the drain pipe.

In your shoes I'd open up the IP's drain plug, let the excess fluid out, and flush with fresh oil. After flushing with fresh oil close the plug and don't add more oil. Then run it and see how long it takes for it to start leaking again. And check that drain pipe per Diesel911's suggestion to make sure it's clear. If it starts leaking again soon after then you will be looking for the source, and if the car runs well chances are the excess fluid isn't coming from the elements. That would finger the lift pump as the primary culprit.

Hope this helps!
The turkey baster thing is something I read in one of the threads here on this forum. Out here in CA they have .99 cent stores that sell them. Coming up with the thin tubing and attaching it is up to the person that is doing it.

What I can remember from the past is that people people slowly pored in the new 40 wt oil letting the old oil drain out while smelling what was coming out for fuel contamination. They continued that till the felt the smell was gone enough and it was believed there was minimal fuel contamination of the new oil.

When I calibrated some of those pumps I simply filled them with Diesel Fuel did the calibration on the machine and drained all the fuel out. Doing that with the different fuel injection pumps reduced the Fuel contamination of the oil in the calibration machine. I was careful to run the Pumps the minimum time needed to do the calibration.

Smaller inline fuel injection pumps often have ball bearings on each end of the cam but more often there is roller bearings on each end. Never had any issues with the bearing using diesel fuel to lube them during the calibration.
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Last edited by Diesel911; 10-12-2021 at 05:04 PM.
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Old 10-12-2021, 06:09 PM
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Hi All. I took out the drain plug and refilled with fresh oil. Next day I lost about 2 tablespoons of oil at the fuel shut off linkage. I verified this by using UV Dye. I removed the drain plug that is beside the lift pump and no oil or diesel leaked out. Also nothing coming from the over flow tube. I am losing oil from the fuel shut off even though the oil level never reaches that high.
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Old 10-13-2021, 04:11 PM
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Oh man, you got me now! I'll have a look inside my "junk" IP to see if anything jumps out at me. I'll post again after I've had a look.

So if you keep running it will it eventually run out of oil and stop leaking?
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Old 10-16-2021, 10:59 AM
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If I was to keep running without checking and refilling the oil it would run out and I would get only some diesel to drip out. I have o-rings coming. Hopefully that
the will fix the problem.
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Old 10-16-2021, 12:30 PM
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FWIW, here are some photos of the insides of the rear end:





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W115 240D injection pump oil leak.-rear-housing_01.jpg   W115 240D injection pump oil leak.-rear-housing_02.jpg   W115 240D injection pump oil leak.-rear-housing_03.jpg  
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  #10  
Old 10-16-2021, 03:25 PM
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Wow. Thank you so much for the great pictures. This give me a good look inside.
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  #11  
Old 10-16-2021, 03:32 PM
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Talked to Tom at Yankee Diesel. He is sending me an o-ring. He said all I have to do is remove the cotter pin and washer on the opposite side of the linkage opposite the arm. Have to be careful not to lose the key. Then the short can be slidden and a new oring installed. I will post if I solve this problem in case another person has this problem in the future.
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Old 12-24-2021, 07:57 PM
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Just an update on the final resolution to the pump leak. It turned out that the major source of the leak was the rectangle gasket on the plate at the bottom of the pump. Thanks to everyone who helped me.

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