OM617 N/A Lift pump rebuild

[guyonabuffalo]

I changed the valves and springs on my lift pump today. It the MW type with the 3 bolts attaching it to the IP.

If you can see the picture - I have positioned the parts the way they are supposed to go.

[Diesel911]

Did you change the O-ring that the green arrow is pointing to?

The Mercedes valve kit does not come with the O-ring.

[guyonabuffalo]

Diesel911, I didnt change the O-ring because I didnt disassemble the spring/drive mechanism. Figured I would leave it alone since it works fine.

However there is a persistent oil leak now, from near one of the 2 bottom screws that hold the lift pump to the IP. I have tried everything, new bolts, tap, new gasket. No luck.

[Diesel911]

Not sure on the oil leak. However, if the 2 bottom studs came out along with the 2 bottom nuts those studs are under the level of the Oil or the studs were not tight. You could need some sort of thread sealant on the threads and also the studs need to be tight.

[BillGrissom]

I also rebuilt the lift pump on my 1985 300D (but ~1982 engine). There were 3 bolts (10 mm wrench) and no studs. But, swapping to studs might help since getting at the bolts is challenging. I used a kit from ebay (~$15), which is fairly generic for many Bosch lift pumps (innards the same, housings vary). I also changed the shaft O-ring shown, using one from my HF kits (probably Viton).

I had a worse oil leak later. Because I didn't have the mounting gasket, and my son needed to leave w/ the car, I used a round fiber gasket from an old Chrysler set I had lying around. But, it was inside the bolt circle. That put a cantilevered load on the mounting ears and one later snapped off. Fortunately, not too much leaking before he returned, I had a spare lift pump, and bought the proper gasket in the meantime. Don't repeat my mistake. Rush jobs usually end like that.

[Shern]

Originally Posted by guyonabuffalo

Diesel911, I didnt change the O-ring because I didnt disassemble the spring/drive mechanism. Figured I would leave it alone since it works fine.

However there is a persistent oil leak now, from near one of the 2 bottom screws that hold the lift pump to the IP. I have tried everything, new bolts, tap, new gasket. No luck.

I'm having this issue now as well... I can't really tighten the bottom Left stud any further given the wrenches I have. Appears to be coming from both bottom studs.

Anyone figure this out?

[Diesel911]

Originally Posted by Shern

I'm having this issue now as well... I can't really tighten the bottom Left stud any further given the wrenches I have. Appears to be coming from both bottom studs.

Anyone figure this out?

At least the lower threaded holes for the studs are open into the oil sump. That means with no sealant or loctite on the threads oil can seep past the threads.

Issues with the gasket like not getting all of the old gasket off and applying the new gasket over that.

Gaskets that come with kits are sometimes extremely thin. I found that also to be the case with the gasket that is between the front of the Fuel Injection Pump and the block where the pump blots on. I used the stock thin gasket as a template to draw onto and to make another gasket out of thicker gasket material.

It could be that the nuts have used up all of the threads on the studs and cannot be tightened more; you need washers between the pump flange and the nut. That is more likely to happen if the gasket is thin.

The pump flange ears are rather fragile. If the pump was installed whith the cam pushing on the roller plunger when you tighten down if not done evenly and carefully it is possible to crack a flange.

Not related to the lift pump but the bottom pan on the pump has been known to leak Oil. If you have an M type pump the side cover can also leak Oil.

You can also get Oil leaks from the throttle shafts or any shaft on the pump that moves.

Concerning a wrench for the little nuts. I lucked out and had a short one that on the box end was on the outside diameter which allowd it to fit and it had a suficient angle to it. It was still slow to use but it fit.
You could go to a cheapie tool shop and buy a single wrench and grind or otherwise modify it so it fits. The wrench dose not need to be of a high quality as not much force is needed to tighten the nuts.

Maybe some metric type ignition wrenches would fit.

Another note I generally use some sort of gasket sealant on nearly all gaskets before mounting them.
I am not a big user of silicon sealant but it can be used if you are careful/stingy with how much you apply.

[Shern]

Originally Posted by Diesel911

At least the lower threaded holes for the studs are open into the oil sump. That means with no sealant or loctite on the threads oil can seep past the threads.

What does this mean exactly? There were three nuts with washer to remove, rather than a solid bolt. The posts themselves seemed to be part of the IP.

The gasket was a pretty standard paper gasket. I was pretty tidy about removing the previous one. Can't remember the position of the roller but I did have to apply some pressure to get the pump back on. I was super wary of cracking a flange ear so made sure to tighten each nut a bit at a time. The washers are still there, but seems I need to get the nuts a little tighter?

[Diesel911]

Originally Posted by Shern

What does this mean exactly? There were three nuts with washer to remove, rather than a solid bolt. The posts themselves seemed to be part of the IP.

The gasket was a pretty standard paper gasket. I was pretty tidy about removing the previous one. Can't remember the position of the roller but I did have to apply some pressure to get the pump back on. I was super wary of cracking a flange ear so made sure to tighten each nut a bit at a time. The washers are still there, but seems I need to get the nuts a little tighter?

Well I had written all of the possible areas were you could have an oil leak. That does not mean they are the cause. I was just giving possibilities.

In the case of the studs that go into the Fuel Injection pump. When holes are threaded there is clearance between the stud theads and the hole threads. The holes in the Fuel Injection Pump for the studs go all the way through. That means it is possible for Oil to seep between the thread clearance between the studs and the Fuel Injection Pump Holes.

The question is why would that happen now. The answer is that sometimes when you remove a Nut that is on a stud the stud backs out a little or a lot. Once the stud moves what ever seal was around the stud threads is broken making it possible for a oil leak past the studs.

Once the Oil gets past the Stud there is nothing to stop it.

I am just adding this. Before installing a Lift Pump a mirror should be used so that you can look through the hole into the Fuel Injection Pump an view the Camshaft inside. The Engine can be rotated which will rotate the Camshaft inside of the Fuel Injection Pump and you do that until you can see the lowest part of the Camshaft area that would drive the Lift Pump. That way when you re-install the Lift Pump you need only the most minimal pressure to push it in while you tighen the nuts.

I miss one spot. On the MW Fuel Injecting Pumps there is an exterior Oil Supply Line approximately behind the Fuel Supply/Lift Pump. It is made of hard plastic. It is unlikely for it to leak but not impossible. Also the Oil in that line is under pressure so a small leak would show up.

[Diesel911]

It is hard to see but in the attached pic the Fuel Supply/Lift Pump kit in this case came with an extra Stud.

[Shern]

Ah, I understand now, thank you.

The gasket doesn't seem to be leaking, it does appear to be all three of the studs. What's to be done? The end of the stud in the attached picture (I have one from the rebuild kit) doesn't appear to be threaded, but affixed by pressure (???).

[Shern]

OKay, brake cleaned last night, did a quick run this morning and confirmed it is seeping from each stud.

I can't be the only person to have had this issue...

[guyonabuffalo]

Hi Shern,

My problem was similar but my leak was from one of the studs.

After multiple attempts, we determined that new holes would have to be drilled into the IP. (We tried tapping new holes etc. to no avail)

I didnt want to risk messing with the IP so I had my friend make a silicone gasket and basically fill out any space within the stud holes and around where oil could seep through. This seems to have solved the problem.

Keep in mind, my car has unknown but high mileage (determined from signs of wear) so I decided not to potentially hurt the IP. You might want to consider re-doing the holes where the studs go and getting it right.

[Shern]

Originally Posted by guyonabuffalo

Hi Shern,

My problem was similar but my leak was from one of the studs.

After multiple attempts, we determined that new holes would have to be drilled into the IP. (We tried tapping new holes etc. to no avail)

I didnt want to risk messing with the IP so I had my friend make a silicone gasket and basically fill out any space within the stud holes and around where oil could seep through. This seems to have solved the problem.

Keep in mind, my car has unknown but high mileage (determined from signs of wear) so I decided not to potentially hurt the IP. You might want to consider re-doing the holes where the studs go and getting it right.

I appreciate the follow-up. The studs were also leaking in my case but a healthy dose of permatex high tack gasket sealant did the job. Coated both sides of the gasket, the mounting surface of the Ip, the bolts, the nuts... It's air tight now.