Question about "MFI Pump" - PeachParts Mercedes-Benz Forum

jmcgill · #1 12-31-2009, 12:59 PM

I had my Mercedes at a local garage for the last week attempting to diagnose where my oil leak is.

He came back to me today saying that I've got a leak at the "MFI pump". He pointed it out to me on his manual (an Alldata version of the W123 manual I have). What he showed me is the oil filter canister, on the bottom where the hoses go. He said there's a pump there that needs to be rebuilt and that's where I'm leaking oil and it's mixing with Diesel. He went on to say that my engine vibration was being made worse by that leak and that it was leaking pressure and causing the motor to run rough.

I have never heard of an "MFI" pump on a Mercedes Diesel, and I was loathe to plunk down more than $800 to have this leak fixed, because I'm not sure what the mechanic was talking about.

Any enlightenment is appreciated!

Thanks,

Joe

Diesel911 · #2 12-31-2009, 04:06 PM

MFI= Mechanical Fuel Injection; what we call the Fuel Injection Pump or by initals IP.
EFI= Electronic Fuel Injection (on gas cars and maybe some Diesels now)

Diesel911 · #3 12-31-2009, 04:25 PM

I took a look at you past Threads and you have not posted on this subject before.
How about some more details on the problem itself.

If you are getting Diesel Fuel in your Crankcase Oil the most likely source is the tiney O-ring in your Fuel Suppply Pump. See the thumbnail pic.
This leaves you with the choice of replacing the O-ring as I did or buying a completly new Fuel Supply/Lift pump.

If you have an exterior Oil leak it could be the Gasket on the Front of the IP or that Gasket at the Fuel Supply Lift Pump. In the 2nd Pic in the yellow square.
Another places the Fuel Injection Pump can leak Oil out is it has a bottom oil pan has a big O-ring and the Throttle Shaft O-rings somtimes can leak.

barry123400 · #4 12-31-2009, 06:33 PM

A new replacement lift pump may get to this type of price with a few other things thrown in plus the diagnosis.. Probably as desiel quoted an easy and cheap repair to do at home. You might save some money if you tell him a rebuilt kit is around ten dollars for the lift pump.

If it does not include the O ring a cheap universal one would do I think Older cars of any make are not prime candidates to go to garages with in my opinion.

They are pretty straightforward to repair for one thing. The other being an older car will requier more trips to a garage than an average new one. So it can be a formula for going broke..

This site could have informed you how the oil was getting in. Plus how to deal with it yoursef. Cost? Possibly an hour or so and less than twenty dollars.

layback40 · #5 12-31-2009, 06:47 PM

Give the area a good clean with degreaser so you can see where the leak is. I would go to another garage. If the vibration is bad, a new engine mount may be required. $800 sounds like a wild guess not a quote.

tangofox007 · #6 12-31-2009, 06:59 PM

Quote:

Originally Posted by jmcgill

What he showed me is the oil filter canister, on the bottom where the hoses go. He said there's a pump there that needs to be rebuilt and that's where I'm leaking oil and it's mixing with Diesel.

That, except for the oil leak possibility, is 100% hogwash. There is no pump in the oil filter housing and there is no diesel fuel routed there. Either your mechanic doesn't have a clue or he is hoping that you don't.

jmcgill · #7 12-31-2009, 07:28 PM

Thanks all!

I thought as much, and I'm going to take the car to another garage on Saturday.

I thought that it was leaking from the canister, and a mechanic (Mitch Carr in Kensington, MD...a well respected place) said it was leaking from there. I had just never heard anything about the pump before. The oil leak is fairly significant...it puts about 8 drops down right after shutoff, and it's leaking when I'm at speed, as evidenced by the oil that goes all the way back on the car. What I was really worried about was him telling me that the pump was causing the vibration problem by leaking pressure in the engine.

I'm going to have mounts put on at another shop, and I"ll have him fix the leak while he's at it.

layback40 · #8 12-31-2009, 07:37 PM

I have never replaced a RH mount. A couple of months after a diesel leak the LH one normally needs doing.

whunter · #9 12-31-2009, 09:09 PM

Quote:

Originally Posted by jmcgill

I had my Mercedes at a local garage for the last week attempting to diagnose where my oil leak is.

He came back to me today saying that I've got a leak at the "MFI pump". He pointed it out to me on his manual (an Alldata version of the W123 manual I have). What he showed me is the oil filter canister, on the bottom where the hoses go. He said there's a pump there that needs to be rebuilt and that's where I'm leaking oil and it's mixing with Diesel. He went on to say that my engine vibration was being made worse by that leak and that it was leaking pressure and causing the motor to run rough.

I have never heard of an "MFI" pump on a Mercedes Diesel, and I was loathe to plunk down more than $800 to have this leak fixed, because I'm not sure what the mechanic was talking about.

Any enlightenment is appreciated!

Thanks,

Joe

Diesel Injection:
http://www.peachparts.com/shopforum/showthread.php?t=142405

OM616/617 Injection Pump.
How to adjust the Naturally Aspirated Injection Pump.
http://www.peachparts.com/shopforum/showthread.php?p=678986

'75 240 D M-style IP Theory - Help!
http://www.peachparts.com/shopforum/showthread.php?p=532895

OM617 IP, oil leak from fuel pump gasket
http://www.peachparts.com/shopforum/showthread.php?t=141338

Fuel injection pump diagrams???
http://www.peachparts.com/shopforum/showthread.php?t=141323

Diesel Timing Chain Link Thread
http://www.peachparts.com/shopforum/showthread.php?t=162071

Diesel911 · #10 12-31-2009, 09:56 PM

Quote:

Originally Posted by jmcgill

Thanks all!

I thought as much, and I'm going to take the car to another garage on Saturday.

I thought that it was leaking from the canister, and a mechanic (Mitch Carr in Kensington, MD...a well respected place) said it was leaking from there. I had just never heard anything about the pump before. The oil leak is fairly significant...it puts about 8 drops down right after shutoff, and it's leaking when I'm at speed, as evidenced by the oil that goes all the way back on the car. What I was really worried about was him telling me that the pump was causing the vibration problem by leaking pressure in the engine.

I'm going to have mounts put on at another shop, and I"ll have him fix the leak while he's at it.

So you are having an external Oil Leak somewhere?

Cleaning the Engine and than taking a look as previously suggested is the way to go.
On mine a Valve Cover leak had caused Oil to go into places you would not think it would go. Ounce the Engine was degreased it was easy to tell where the problems were.
I would degrease before taking it to another Mechanic.

Archdukeferd · #11 12-31-2009, 10:09 PM

Quote:

Originally Posted by Diesel911

I would degrease before taking it to another Mechanic.

I hate paying other people to clean my stuff. I also like knowing what I'm taking to a mechanic which requires getting a good look at it.

+1 more on the degrease.

kerry · #12 01-06-2010, 07:00 PM

There's either a failure to communicate or a deliberate attempt at bull**** in that diagnosis. If you are leaking oil in the vicinity of the oil filter housing, the typical culprit is the oil filter housing to block gasket. I see no connection at all between such a leak and the engine running rough.

Can you give any more detail on the rough running engine.

jmcgill · #13 01-06-2010, 07:03 PM

Your running symptoms sound nothing like mine. My car runs better when warm, doesn't smoke except upon startup, and seems to be leaking from just that one place.

I've got it at another mechanic who some on the board here have recommended, so we'll see what he says.

I really wish I had the time to get under the car and degrease, but I work too late, and can't do it.

jmcgill · #14 01-06-2010, 07:07 PM

When it's cold, the steering wheel vibrates so badly I don't want to hold it....however, when I don't hold it, it make so much noise, I have to keep my hands on it.

The majority of the vibrations come through the steering wheel, and are further to the front of the car. They're the worst at idle when the car is in drive. At idle in Reverse, the vibrations are much less.

The mechanic it's at now says the engine mounts are the cause of the vibes...I tend to agree with that diagnosis.

kerry · #15 01-06-2010, 07:14 PM

Quote:

Originally Posted by jmcgill

The mechanic it's at now says the engine mounts are the cause of the vibes...I tend to agree with that diagnosis.

Much more reasonable than the prior diagnosis.