Refreshing the fuel pump on an OM617 (European spec – non turbo) - PeachParts Mercedes-Benz Forum

Stretch · #1 02-21-2011, 09:32 AM

I'm not sure how useful this will be as the majority of the readers on this forum seem to own a turbo version, but I'd thought I'd start the thread anyway as I haven't seen much information on fuel pumps in bits on this forum.

The fuel pump that is the subject of this thread is slightly simpler than the version that is fitted to the turbo OM617s – for more information and pictures see this thread (fuel pump). The pump I have has the following Bosch part number on the front => FP/K22M101.

The mechanical fuel pump on an OM617 is situated on the side of the injector pump.

It is a very simple pump. A plunger shaft, that runs off of a cam inside the injector pump, pushes against a sliding piston and spring inside the fuel pump. This provides the basic pumping effect; whilst the flow of fuel is ensured to flow in one direction by two non-return valves.

Stretch · #2 02-21-2011, 09:33 AM

To remove the pump from the injector pump you need to undo two pipes – plug and bag them to stop dirt ingress and fluid loss – and two nuts which hold the pump onto the injector pump. You will find it handy to push against the pump whilst you undo the mounting screws as the plunger spring will try to push the unit away from the injector pump.

I've read (on this forum) recommendations that it is best to remove the large 30mm hexagonal cap that holds the spring in place before removing the fuel pump from the injector pump. If you decide to do this I advise you to be very cautious. My 30mm cap was well and truly stuck in place.

As I had already removed my fuel pump I bolted it to a sturdy piece of wood...

...the torque that I managed to apply with a 620mm bar just bent the bolts.

I didn't fancy risking damaging my injector pump for the sake of a fuel pump. I was thinking, injector pump bloody expensive; fuel pump comparatively cheap! I think you are better off trying to remove this 30mm hexagonal cap by clamping the fuel pump with sacrificial bits of wood in a vice.

You are less likely to cause any serious damage.

Inside the 30mm cap you'll find a copper washer, a spring, and a piston. Remove these bits for cleaning.

Stretch · #3 02-21-2011, 09:33 AM

Next you can tackle the hand pump (17mm spanner)...

...and the two unions (both 22mm)...

The plunger shaft can just be pulled out from the end of the pump.

Don't forget to remove the small sealing rubber O ring for this shaft.

Stretch · #4 02-21-2011, 09:34 AM

For cleaning I mostly used brake cleaner with engine cleaning brushes (I really need to buy a parts washer!).

As the fuel pump body is a pretty sturdy casting I gave it a good going over with my angle grinder and wire brush attachment before I masked up the holes for a repaint.

I repainted it with POR15 engine enamel to match the colour of my newly painted engine block.

Stretch · #5 02-21-2011, 09:34 AM

Look out for any obvious damage on the external and internal surfaces. Pay particular attention to the moving parts. I was lucky – the piston and plunger shaft were only lightly polished. The plunger shaft on my pump has a diameter of 5mm.

The strength of the suck of the pump will ultimately depend on the fit of the piston in the main body of the pump. If the pump seems to be worn out then I guess you are better off replacing it, though I guess a decent machine shop would be able to fit a liner and hone the internal diameter to suit your existing piston. Alternatively you'll find lots of information here on this forum concerning the use of electric fuel pumps as an alternative to the original mechanical.

Make sure that the non-return valves are as clean as you can get them and make sure that the little valves operate properly on their springs.

WARNING:- Be careful don't push too hard!

Stretch · #6 02-21-2011, 09:34 AM

As a rule it is best to replace the copper washers and the rubber seals.

I've got a supply of metric O rings and copper rings that I used. I don't have the part numbers for the official parts – there must be a repair kit – perhaps someone can help?

Don't forget to fit the small O ring in the back of the housing.

Lubricate it with engine oil before fitting – and be careful not to pinch the seal when you push the plunger shaft into position. I then lubricated the piston with engine oil and fitted it with the locating part for the spring in the correct orientation.

Don't swamp the pump with engine oil when you are doing this. You only need a small amount to help with the assembly – when you fill the pump with diesel, the diesel will take over the task of lubrication. Fit the spring and the 30mm cap.

Stretch · #7 02-21-2011, 09:35 AM

Pay close attention to the orientation of the non return valves that are fitted below the two fuel pipe unions – and don't forget to put in the bent steel spacer above the non return valve on the injector pump side of the pump.

Re-fit the unions and tighten with a 22mm socket / spanner. Then fit the hand pump.

Stretch · #8 02-21-2011, 09:44 AM

Well that's all folks – nice and easy – nice and simple!

The only tricky thing in my opinion is getting that 30mm hexagonal cap off without damaging it or something else.

Before you fit the pump to the injector pump I think it is a good idea to fill the pump with some fuel to give the hand pump a helping hand for when you bleed the system.

layback40 · #9 02-21-2011, 09:21 PM

Another well presented DIY from Army !!!!!

Diesel911 · #10 02-22-2011, 12:33 AM

Indeed.

SpecialDelivery · #11 06-17-2011, 06:53 AM

Great job thanks for posting such an excellent tutorial!

layback40 · #12 06-17-2011, 08:37 AM

Quote:

Originally Posted by Army

Next you can tackle the hand pump (17mm spanner)...

...and the two unions (both 22mm)...

The plunger shaft can just be pulled out from the end of the pump.

Don't forget to remove the small sealing rubber O ring for this shaft.

I see in the first pic you were using a "Texas Micrometer", Later on you used a conventional one!!

ckamila · #13 02-14-2013, 09:27 PM

Stretch - Any difference between turbo and non turbo lift (fuel) pumps...or is there only ONE pump?

Oh, missed the thread title (European spec – non turbo).

Thanks,

Chris

Stretch · #14 02-15-2013, 03:44 AM

The turbo IP has a slightly different looking pump - instead of a plunger it has a roller.

Picture found in this thread

OM617 Part ID: Lift Pump?

cook · #15 02-17-2013, 10:00 AM

I wonder if that is the same roller bearing MB uses in the vacuum pump? If it is, I wonder if any of them had the plastic race that disintegrates over time. I'm thinking about the vacuum pump failure threads elsewhere on the forum where the bearing comes apart.

So lets say they did use the same plastic race.... Is there enough clearance for the ball bearing to get out of the pump and get into the engine?

(Also, that non-return valve looks to be the same one used in the vacuum pump.)