Help please! Fuel pump massive oil over flow trough engine oil line

[EarlypagodaMX]

Hello please help me find my the cause of my problem. My car is a very early 230sl 1963 with no oil circuit to the fuel injection pump.

I just picked up my fuel pump from a full rebuilt and installed back in the car.  It ran like a champ for the first hours. Earlier today I noticed that the pump was pouring oil from the red oil feeder cap.  First I thought that the oil was being flooded with gasoline in a massive way, but there was no gas in the oil. Then I checked the engine oil level and I realized that  I lost more than 2 liters of  engine oil from there.

I suspect the line from the engine to the pump that has a check valve eve though I read the article from here, I still don't understand how it works or why is there

Please help me, I'm in the dark  here. I'm  attaching 2 pictures (one I took from this web page.

Best regards,

Eduardo

[EarlypagodaMX]

Has anyone tried to cancel the check valve? So no oil goes from the engine to the fuel pump

[Shvegel]

Eduardo,
is there any chance the small oil line is reversed?  the fat end(check valve?) is attached to the injection pump in the picture on our site in the technical manual.

[EarlypagodaMX]

It was installed just like in the picture,   When I disassembled the check valve I noticed that with oil pressure from the engine it opens up,  it doesn't make sense, my pump doesn't have an oil return line or hole. Unless the check valve spring is to weak now, but it doesn't seems like it was to strong in the first place

[Naj ✝︎]

Has anyone tried to cancel the check valve? So no oil goes from the engine to the fuel pump

You should not cancel it. It supplies lub to the plungers. Maybe the check valve is stuck open?

See orientation pic.

[EarlypagodaMX]

It was mounted just like that, I checked the valve and was not stuck opened when I revised it, there was a cascade of oil pouring out of the red cap.

Is it possible that some thing got loose inside the pump and now is oil that should be in the plungers going trough the pump oil tank.

What I don't understand is the oil circuit. There is a flow of hi pressure oil going trough the engine to the pump but there is not a return line. 

[Benz Dr.]

That small check valve is strictly one way. It allows oil into your IP but won't allow anything to go back into your engine. It will open with as little as 7 PSI pressure and is designed to close at idle so that any oil which contains fuel from the IP is prevented from backing up into your engine oil. You need those parts so don't remove them.

Send you IP back to your guy who rebuilt it. Probably a broken seal or something inside the pump.

[EarlypagodaMX]

Thank you all

Dr. Benz

How the oil goes back to the engine? Or it just holds a constant oil pressure inside that IP chamber and that chamber does not communicate to the oil deposit inside the IP?

Thank for sharing with me

[Benz Dr.]

I know how it works but it's not easy to explain it. Your problem is inside your IP so don't worry about the check valve. You can take the check valve apart and make sure the small pin inside is freely moving but that's about all you need to do.

[wwheeler]

The early pumps have two oil areas and are separate. The oil line feeds pressurized oil to the plungers and the rear oil reservoir lubes the mechanisms in the back. The rear one you have to manually change.

The later pumps have no separate rear oil reservoir. The engine oil line feeds the whole pump. There are good pictures and such in the tech manual. As Dan said, sounds like there is a gasket or such missing allowing pressurized oil into the rear chamber. I'd send it back too.   

[Benz Dr.]

There is an oil drain hole in the front of the pump near the splined drive. The oil drains out there and back into the engine via the large casting hole for the pump. With the pump out and tilted towards the front, oil will dribble out here slowly. The early pumps have two oil areas and are separate. The oil line feeds pressurized oil to the plungers and the rear oil reservoir lubes the mechanisms in the back. The rear one you have to manually change.

The later pumps have no separate rear oil reservoir. The engine oil line feeds the whole pump. There are good pictures and such in the tech manual. As Dan said, sounds like there is a gasket or such missing allowing pressurized oil into the rear chamber. I'd send it back too.   

Only the 280SL pumps have an oil drain near the front drive flange. This is why there is no need for a check valve in the oil line for 280SL.

 Early cars have a crankcase and a dip stick to monitor oil level. I believe that early cars have two portions to the crankcase but they are inter connected so that the oil remains at the same level for both areas. I've never had one apart so I won't say for 100% certain but I'm fairly confident on this. The oil feed line is only supposed to lube the injection elements and prevent both fuel and oil from entering the lower crankcase where it would quickly dilute the lubricating oil with gasoline.

[wwheeler]

I will have to check tonight on pictures of an early pump regarding the drain hole. I do know that both the early and late pumps have valves. They are in different places and may do different things. The valve on the on the 280 screws directly into the pump block on the back side. The early version has the valve in line and just before the fitting going into the pump block. The oil fitting on the engine block comes off the same spot whether it is a late or earlier pump. So it is the same pressurized oil regardless.

If there is no drain on the early pump, how does the oil circulate from the supply oil line coming into the pump, or does it? The injection elements either just get pumped up from the oil line similar to an oil gauge, or it goes somewhere back into the engine. Who knows which?

[Charles 230SL]

Here's a couple pics of the front my R11 pump; there's no drain holes (my car is chassis #3548). Appears the oil line holds constant oil pressure on the pump - don't the 6 plungers use oil pressure to "seal" the walls of the elements/cylinders?

[wwheeler]

I have been enlightened. You have to think of the early and late pumps as having two separate oiling systems. The front system that is fed by the tube on the engine block. And the rear system.

The front system is the same on both pumps and both have check valves. Different locations, but same operation. There is no oil drain back on the front system and the check valves maintain pressure so that there is a constant oil film on the plunger pistons for sealing.

The rear system is what differs between early and late pumps. The early pumps have a reservoir with dipstick and vent cap that must be manually checked and replaced. There is NO oil drain back into the engine on the early pump and I was wrong about that above.
The late pump uses an internal branch from the engine oil line to feed oil into rear case. It DOES have an oil drain back into the engine and as the oil fills up from the oil feed, it drains back into the engine. The oil drain hole is on the front right next to the splined drive.

Now concerning the original post with an early pump, there must be something that was incorrectly installed to allow the oil from the pressurized engine oil line to fill up the rear case. That of course makes sense because there was oil loss in the pan. So the oil had to have come from the pressurized oil line and made its way into the rear case. The oil had no where to go and overflowed. 

[Benz Dr.]

The late oil line has no check valve and a simple banjo bolt screws into the pump. Are you saying that the fitting it screws into is actually a check valve or that it has one incorporated somehow? I never looked for something like that and I always figured the oil simply flowed into the pump, lubed the injection elements and then returned via the drain hole at the front of the pump. The check valve is only there to prevent fuel diluted oil from backing up into your engine oil while your engine is at idle, all while being under 7 PSI or less. Frankly, if your engine has oil pressure that low it already has big problems anyway. 

[wwheeler]

The attached is from the tech manual. The early one has a banjo fitting in the back, but the late one is a fitting and the oil line has a flare type fitting that attaches to that. Mine is the same way. Not sure what it does precisely. It is part number #000 074 14 86 and I have one in my parts box. I will have to have a closer look at it and post pics tonight.

Quickly looking at it, it has tapered pipe threads on one end and a flare fitting on the other where the oil line attaches. On the pipe thread side that goes into the pump, there is a small hole maybe 1mm. The other side you can see some internal parts. So it is just not a plain straight through fitting adapter. It does something. But what?

[Benz Dr.]

Likely a metering valve. You would quickly flood the pump with oil if you allowed a full stream of oil to enter without one.

[wwheeler]

Here is the part. 1st the Bosch tag. 2nd, the side shot showing one side tapered pipe thread and the other a flare fitting. 3rd, the end view of the part going into the pump. 4th, the other end view where the oil pipe attaches to.

Clearly there is something other than a small hole inside this device. If you blow into the flared fitting side as if it were oil pressure, there is some restriction. But I believe this is just because the 1mm or so hole is creating the restriction. Blowing the other way is a little strange. It is not a check valve in that the air flow is completely blocked. But is somewhat restricted. And it is not like it opens at whatever pressure, both sides flow at even the smallest of pressures. Now maybe at a higher pressure than my mouth can generate (which ain't much), the device shuts off going back into the oil line. Not sure and I am not going to risk ruining the part testing it.

The 1mm hole reminds me of the restriction used on an oil gauge fitting. And maybe the oil system on this side of the pump is similar to that in that the oil pressure builds and stays with very little actual oil flow. To create a sealing oil ring on the plungers to overcome the 220 or so PSI of the fuel, you would have to have a good amount of oil pressure.

So this device on the later pumps isn't a true check valve and not sure what you call it or what precisely it does. I do know that the valve on the earlier pumps is a check valve and I have taken that apart for cleaning. So it stands true that the oil line check valve was eliminated on the later pumps. But it was replaced by this part.   

[wwheeler]

One other question regarding the oil lubes on the pumps. According to the tech manual, R11 (230SL) and R18 (250 SL) had the check valve and the separate rear oil reservoir. The R18V and R18Y (250SL) eliminated the check valve but still had the separate oil reservoirs. It wasn't until pump R20 and above (280SL) that the pump used the full automatic oil lubrication.

If that is true, then it appears that the check valve and the rear oil reservoir have no correlation to each other?   

[wwheeler]

Likely a metering valve. You would quickly flood the pump with oil if you allowed a full stream of oil to enter without one.

Yes it now looks like this is a flow regulator and similar in function to the one for the fuel outlet. And in the case of the later pumps with full automatic lubrication, prevents too much oil flow into and out of the pump. For some reason they replaced the check valve with this regulator valve in the late R18 pumps that still had a separate rear oil reservoir.

[EarlypagodaMX]

Thanks Wallace and Dr Benz

You are absolutely right, it turned out to be a broken housing were the seal of the plunger cylinder #3 met,  it could be repaired but has not been tested yet. On top of that I think they were not the correct seals.

We discovered that one of the plunger cylinders don't have the lubrication hole, the pump had a previous repair and probably this one was exchanged. So that leaves me with my next post, were to get spare parts for my pump

Best regards

Eduardo

[Benz Dr.]

I have been enlightened. You have to think of the early and late pumps as having two separate oiling systems. The front system that is fed by the tube on the engine block. And the rear system.

The front system is the same on both pumps and both have check valves. Different locations, but same operation. There is no oil drain back on the front system and the check valves maintain pressure so that there is a constant oil film on the plunger pistons for sealing.

The rear system is what differs between early and late pumps. The early pumps have a reservoir with dipstick and vent cap that must be manually checked and replaced. There is NO oil drain back into the engine on the early pump and I was wrong about that above.
The late pump uses an internal branch from the engine oil line to feed oil into rear case. It DOES have an oil drain back into the engine and as the oil fills up from the oil feed, it drains back into the engine. The oil drain hole is on the front right next to the splined drive.

Now concerning the original post with an early pump, there must be something that was incorrectly installed to allow the oil from the pressurized engine oil line to fill up the rear case. That of course makes sense because there was oil loss in the pan. So the oil had to have come from the pressurized oil line and made its way into the rear case. The oil had no where to go and overflowed.

From what I understand, it isn't oil pressure that seals the pistons but rather a small groove in the side of the pistons, which when filled with oil, will act very similar to a piston ring. I'm sure engine oil pressure plays a part in this because that's why a check valve was needed to prevent back feed at low oil pressures while idling. Check valve will open at only 7 PSI so it seems to me that it's oil and not so much oil pressure that makes the whole thing work.  Oh, those clever Germans.........

[wwheeler]

That is great news Eduardo! And the other good news is that because of your issue, the entire oil lubrication system was discussed here and I would say we came up with a good resolution of how it works and the differences between the early and late versions.