OM61X Injector Pump Service

[Screwdriva]

Greetings,

I have a 1976 W115 240D and a 84 W123 300D, the former has its own oil supply.

I've had the lift pump rebuilt and the primer pump replaced for both cars. They perform great now so no major issues other than a burning smell in the W115's exhaust, especially on startup.

I wanted to ask if any commonly known replaceable wear or service parts contained within the injection pump can/ should be replaced eventually due to wear? If so, what symptoms do these exhibit when its time?

(I'm not talking about obscure anomalies here.)

Thanks!

[greazzer]

The IPs are pretty tough. They probably go a half million miles before they need a rebuild. Finding a good rebuild shop may be tricky

[greazzer]

The IPs are pretty tough. They probably go a half million miles before they need a rebuild. Finding a good rebuild shop may be tricky

[Screwdriva]

I've heard this anecdotally but also heard that there are perishable parts inside the pump itself.

[barry12345]

What about checking the injectors for spray pattern and pop pressure?

[Diesel911]

You essentially said they were running well. That usually means leave things alone.

The IPs need occasional re-timing. I can't give you a mileage on that.

On Fuel Injection Pumps that use Vacuum the Diaphragm gets old and less flexible and the housings that the rather small Shafts go through wear and or need new O-rings. There is a test for leaks in the Service Manual and on this forum.

[Diesel911]

You essentially said they were running well. That usually means leave things alone.

The IPs need occasional re-timing. I can't give you a mileage on that.

On Fuel Injection Pumps that use Vacuum the Diaphragm gets old and less flexible and the housings that the rather small Shafts go through wear and or need new O-rings. There is a test for leaks in the Service Manual and on this forum.

[Shern]

Originally Posted by Screwdriva

Greetings,


(I'm not talking about obscure anomalies here.)

Thanks!

Unfortunately, it's all obscure anomalies that lead people to messing with their pumps.

Assuming you have an MW pump, there are only a few user replaceable parts (without a bosch bench). Below the hardline pipe connection, is a spring, a Delivery Valve set (plunger and barrel), and a specialty sized copper crush washer. That's it.

If the crush washer has eroded, your IP will be leaking at the line.
If the Delivery valve is worn, you might experience a "hot rough idle."
No idea what happens when the spring is worn... pretty durable thing, can't imagine it happens often.

[Dan Stokes]

Dieselmeken is my pump shop. The MW pump that I removed was working fine at around 200K miles and I'm pretty sure it had never been touched. My performance pump is an M and was thoroughly redone when I installed it probably 100 miles ago (Mutt doesn't get many miles) so I don't know of any issues on the M pumps. I'd say yours ought to be fine for many years to come.


Dan

[Diesel911]

Because people don't understand how the Fuel Injection Pump works it becomes like a mysterious black box that get all the blame.

Mechanics trained as Diesel Mechanics are extremely rare in Car repair shops.

And said repair shops are mostly parts replacers. They will keep replacing parts for you at your expense till you get fed up with them and go someplace else or they happen to get lucky. That happens because they don't know how to trouble shoot diesels and to a lesser extent Mercedes.

[Screwdriva]

Originally Posted by barry12345

What about checking the injectors for spray pattern and pop pressure?

Greazzer did that for me (w/ new Monark nozzles). Also rebuilt my lift pump.

I had heard about a leather diaphragm inside these pumps...must have been my imagination?

[barry12345]

Not your imagination. The 115 injection pumps had them. Failure with age seems to be known. Exhaust fumes that sting your eyes are unburnt fuel.

There is an intake flap on those cars as well. I think. This sounds like the engine is not getting enough air to burn the fuel supplied properly. When those fumes are present.

I might go through all the old posts I can find on those 115 cars. Then test and repair only what tests as defective. There is no indication the injection pump needs a real rebuild. Your injection pump could be very retarded injection timing wise for these symptoms as well. Just usually not the issue with your description and the earlier injection pump.

[Screwdriva]

No eye stinging going on. Just a really strong burning smell coming from the exhaust, most prominent during warm up and a shaking engine idling at anything < 950 rpms. The car runs very strong, no black/ blue smoke at all, healthy compression, 30+ mpg etc. Everything around the pump has been replaced or rebuilt to the highest possible standard.

(For reference, my W123 300D does not have a burning smell at the tail pipe)

[Diesel911]

Originally Posted by Screwdriva

Greazzer did that for me (w/ new Monark nozzles). Also rebuilt my lift pump.

I had heard about a leather diaphragm inside these pumps...must have been my imagination?

People say the diaphragm is made of Goatskin. Whatever material it is made of it is so flexible it is creepy. It has zero resistance to moving.
The closest thing it acts like is black oiled cloth but of course it is not porous as cloth would be.