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Replace O-ring fuel pump.

More and more visitors to dedieseldokter.nl ask me why fuel is leaking on top of the fuel pump and how this can be remedied. Mechanics who come by indicate that the fuel pump must be overhauled, while it is a simple o-ring of less than 1 euro. I think this job can be done for the average boat owner who does his own maintenance on his marine diesel. I have made a step by step guide on how to replace the o-ring. The o-ring suddenly fails and may leak slightly, but also so badly that too much fuel gets under the engine. As far as I can estimate it mainly goes wrong with marine diesel with Bosch fuel pumps of 30 years and older. The pumps have been used on various brands and types of marine diesels. The manuals can be applied to all these brands because the fuel pumps are all the same. In this piece I am using the fuel pump from the MD11 where I am going to replace the o-ring of the delivery valve holder. This part is the same as the Volvo Penta MD series 2000 series diesel engines and can also be found on various Ferymann diesels.

The fuel pump of a diesel engine is a reliable and complex piece of technology that lasts a very long time and does not require any special maintenance. Yet at a certain point the point comes when the pump, for example, starts to leak fuel. This piece is about replacing an o-ring that will keep fuel from leaking from the fuel pump at the low pressure section called the “fuel gallery”. You come across the fuel gallery at in-line fuel pumps that are on the Volvo Penta MD11, among others. The fuel pump is mounted in the engine block and on the top part of the fuel pump that protrudes you will find the fuel supply hose that comes from the fuel pump and the high pressure pipe (s) to the injector (s). Before you start this job, make sure that the fuel pump is properly cleaned, no dirt should get into the fuel pump when the delivery valve holder has been removed.

I do the cleaning with a degreaser and with compressed air from an aerosol.

Degreaser link.

Compressed air spray link.

Volvo Penta O-rings and copper sealing ring link.

Yanmar O-rings and copper sealing ring link.

Fuel pump cross section.

The drawing of the fuel pump clearly shows which parts are in a fuel pump. The O-ring to be replaced is No. 7 in the drawing.

High pressure pump where the fuel comes out of the outlet valve connection

Remove the swivel of the high pressure pipe with a spanner 17. If the engine has several cylinders, it is advisable to also replace the O-ring of other discharge valves.

Loosen the delivery valve holder with a wrench 19. Note that there is a spring and plunger in the delivery valve holder to close the fuel after injection, this is easy to find, so be careful when loosening the delivery valve holder.

Discharge valve holders with 0-ring that must be replaced. The copper ring, spring and plunger can be found in the delivery valve holder.

Place the copper ring and spring with plunger.

Place the delivery valve holder over the spring with plunger and tighten it by hand and then tighten it securely with an open-end wrench 19.

Refit the high pressure line to the injector on the tailgate and loosen the swivel at the injector to bleed the high pressure line by running the starter motor for a short time.

Pay attention!!! Close the sea cock due to with a risk of water hammer. With each revolution of the engine, the impeller pump will pump water into the unload system, but since there are no exhaust gases to force it out, the engine will fill up with water when the seacock is still open.