Inj Pump Oil level

[hands_aus]

I have been doing a fuel usage study on my car and I notice when the economy changes for the worse or better. It is an early 250sl with the “self-contained with dipstick "early" variety” injection pump.

When I first bought the car 3 years ago I was getting 9 MPG but now after many corrections to the linkages and the air/fuel mixture I generally get around 15.5 MPG around town. Also I removed about 500ml of oily black sludge.

Last time I filled it there was a change in the economy hence this investigation.

As part of my research I have been reading the excellent INJECTION PUMP TOUR topic by Joe Alexander see here
http://sl113.org/forums/index.php?topic=790,pump,tour

From The Injection Pump Tour……
“in reality there is no seal as we know it, just an "oil seal". Naturally as things wear or oil becomes dirty or contaminated, the "oil seal" becomes less effective and some fuel or oil may wash by the seal and cause the level in the pump to rise!”

In the last 12 months I have travelled 3600Km and am almost due for an oil and filter change and grease. It is done 12 monthly.

After checking my oil level in the Injection pump I found that the oil level had grown to the point that the Injection Pump was definitely over filled by about 100ml.

This afternoon I changed the Injection Pump oil. There was about 300ml of black oil.

I think that I need to change the injection pump oil every 6 months.

What do you folks with Injection pumps with reservoirs do?

How can I check if there is wear in the piston shafts?

Should I worry or just live with it and check the Inj pump oil more often?

Tomorrow I will take the car for a run to see if the economy is back to normal.

Any advice greatly appreciated, thanks

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[Naj ✝︎]

Hi, Bob,
My 'garage queen' 230 had a rebuilt pump when I bought it 4 years ago.
I have managed to put on about 3500 miles. The oil in the pump is clean and new looking and the level is same as when I checked the first time I learned about it.
I wonder if the amount of additional oil from the engine is an indicator of the wear in the pump elements?

naj

p.s: Your (& George Des) fuel pump article is excellent. I stripped the pump two weeks ago and was able to get all the 'o'rings and bearings as quoted.
Will probably rebuild next week.
Thanks again
naj

65 230SL
68 280SL

[A Dalton]

Excerpt from an article by Bob Fairchield [ pump rebuilder]

>>>SLML: What can owners do to prolong the life of their pumps?

FAIRCHIELD: "Monitoring the correct level of oil is important. There are two portions of the pumps that receive lubrication... the lower portion has its own fillable oil reservoir. All except the 280SL have a dipstick that can be checked. Too much oil is as bad as too little. Lack of lubrication is obvious too much inhibits proper advancement of the flywheels that are in the lower portion... and this allows the pump to run too rich. Overfilling on 220, 230 & 250 engines can be caused by careless servicing, or by leaky "0" rings from the plunger chambers up above. The upper parts receive lubrication separately. Leaky "0" rings will cause flooding of the lower pump chamber (in 280SLs overflow drains back into the engine). In addition to poor M.P.G. running too rich washes oil off cylinder walls (maximizing wear) and diluting oil (destroying main bearings). Maximum permissible oil dilution is 5 percent.">>

[rwmastel]

quote:What do you folks with Injection pumps with reservoirs do?

Check it a couple times a year.

quote:How can I check if there is wear in the piston shafts?

I don't know, I guess just check the rate at which the IP oil resivoir fills up.

quote:Should I worry or just live with it and check the Inj pump oil more often?

Just check the level more often and find out how many ml of oil is gained per 500km (or some volume/distance rate).  You need a base line.[/quote]

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[hands_aus]

Thanks guys.
I was thinking that since the oil level increases over time, I would only add enough oil to reach the bottom mark of the dip stick.
This then would allow a longer period of time before the oil level creates a change in the economy by interferring with the govenor weights.
It would also be within specs for the injection pump.

What do you guys think?

Your help is always appreciated

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[A Dalton]

<<What do you guys think?
>>

 The reason the oil level comes up enough to interfere with the fly-weights is cuz gas is adding to/diluting the oil,  So, if you go with a low dip-stick reading thinking it will take longer to overfill , you are correct, except you now will have a res full of gas diluted oil to lube your pump
 I certainly would not want my pump lubed with gas diluted oil..that's for sure.

[Cees Klumper]

Is there a quick fix to the leaking 'o' rings that cause the flooding of Bob's pump reservoir? Or does it have to be rebuilt profesionally for this?

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[hands_aus]

The "Tour" says Quote "Inside the cylinder is a tiny groove ringing its circumference. The metal oil tube in question supplies this groove with oil under pressure from the engine. This is a near perfect seal!

it does a very good job sealing the plunger and which keeps the fuel out of the bottom end of the pump and enables the fuel to be pressurized and metered for injection. So in reality there is no seal as we know it, just an "oil seal". Naturally as things wear or oil becomes dirty or contaminated, the "oil seal" becomes less effective and some fuel or oil may wash by the seal and cause the level in the pump to rise! The engine oil pressure at idle should exceed the fuel pressure at idle or the overpowering fuel pressure will also bridge the "oil seal"." end quote

There was no smell of fuel in the oil I removed but that doesn't mean it isn't there.

The amount of oil added was 150ml and that showed about half way up the dip stick.

There is a check valve on the small oil line to the injection pump. Is it possible that could cause problems with the oil pressure to the Inj pump?

It seems that in the future I will need to have the Inj Pump rebuilt, but for now, I will, as suggested, closely monitor the level of the fluid and change it more often.

Thanks for your help

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[Naj ✝︎]

Bob,
What spec engine oil are you using at the moment?
Do you think using a heavier spec oil in the engine would improve matters?
Should be a fairly easy task to check the oil line valve - ya?
naj

65 230SL
68 280SL

[A Dalton]

A Thought on the matter...

I remember talking this over with a fellow MFI friend years ago and the thought came up that if one saw a gradual increase in dip stick level on the early  pumps with the inferior sealing cone style check valves [ as opposed to the later ball checks ] , this could be a possible cause .
 The main complaint [ and reason for upgrading to ball valves] was a stumbling of the engine at start-ups after sitting for periods... where the cones would not hold fuel injector line pressures when engine was at rest. This allowed the line fuel to back feed its way  to the plungers. [ no check]  This  stumbling would clear up after a few moments of running as the lines replenished. {The new ball valves solved this problem}
 But at the same time , the thoughts were that these leaking cones could also allow fuel past the 'Oil Lock" design of the plungers as a  resting engine would not supply the lock groves any oil pressure from the engine feed  to complete the seal..thereby allowing the fuel lines draining to wash out the oil required by  sealing lock and wind up in the res.
 .. Has anyone had a stable oil res level after modifying the pump to the ball valves that had a level problem prior ?? Guess that would verify the theory..
 My guess is it is a possibility..

[hands_aus]

Hey Naj and Arthur,
Naj,
I use Penrite HPR30 20W-50...same as the engine. I don't think I would use a heavier type oil.
One comment on ambient temperatures...Brisbane (sub tropics) is never colder than about 4 Celius. 2 Celius would be really extreme.
Summer can be 39 C, sometimes hotter, but not often, usually in the top 20s.

Not sure how to test the check valve. Maybe clean it out and then air pressure test it by blowing into it in the reverse direction. This is how I checked the check valve on the electric fuel pump. It seemed to be accurate enough.

Arthur, I installed that 1 second relay (works great BTW) to get around that problem of leak back on my inj pump.
It is possible they are related problems.

Question..
Can the new type ball valves be easily added to the old type Inj Pumps
Or do the inj pumps have to be modified?

Thanks

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[A Dalton]

<<Question..
Can the new type ball valves be easily added to the old type Inj Pumps
Or do the inj pumps have to be modified?>

 The ball check valve upgrade was just a factory modification after pump R-18y and you simply take the old one and put the new in..
 The part # for the ball design type is 000 074 17 15

 Any of the later [ R-20 and beyond] with crankcase oil force feed lube,  have the newer style ball checks ..

[hands_aus]

Thanks I will keep the information for when I need it.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[J. Huber]

I just tried to check my FI oil level (early pump) -- and cannot budge the dipstick. Am I remembering correctly that it turns counterclockwise? Is it under pressure at all? Sorry, very novice question -- its why I have kept mechanics in business all these years!

James
63 230SL

[A Dalton]

RH thread..CCW to loosen

[Benz Dr.]

Different injection pumps have different parts inside so you have to separate them into early nd late pumps. There's also a pump that has some features of both late and early systems.

The early pumps have O rings at the bottom of the plungers and there are two different sizes depending on the model of pump. The oil lock on the plungers will hold gas from leaking down into the crankcase but wear and engine heat can make this area leak. Engine oil and the test oil used by the rebuilders won't leak through there but gas will - it will leak through almost anything.

The check valves in the delivery lines going to the injectors will hold fuel in the lines after shut down. Delivery valves are basically similar to those used on diesel pumps and normal wear can cause either of them to leak back.

Any fuel in the system simply drains back through the return line going to the fuel tank. Some fuel could seep by the plungers if there's a lot of wear in that area.  I had a pump that would overfill the crankcase but after being rebuilt the oil level never moves and all the injection plungers were not changed. New O ring seals were installed and that made the difference.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org

[A Dalton]

I agree.
 Basically, I think if one sees a rise in oil res. dip and it contains blackened oil, the suspect would be the O ring seals allowing engine oil feed through to the lower cavity. And if one sees a raising level of gas diluted oil in res. , then the suspect would be worn plunger sealing , leaking  line check valves , or no oil feed to pump for Oil Lock/Sealing..in which case a possible failure at the oil feed line check valve would be suspect..