Assessing a used Yanmar 8HP diesel engine

[HorseshoeBay]

After cleaning and reassembly, the rack on the fuel injection pump moved freely as per the manual’s test.

However, after reinstalling the injection pump nd turning over the engine - disaster!

The plunger seized ind the barrel and the cap under the end of the plunger broke.

Sunity advertise IPs, however the governor attachment looks external.

Does anyone have experience with installing a Sunity IP or finding a replacement Yanmar IP?

[mcpusc]

> Sunity advertise IPs, however the governor attachment looks external.

the YSB & YSE IP is completely different from the YSM — you must have the YSM.


the early engines have a very simple IP with a fixed volume plunger and a bypass valve. on them the governor linkage is external, and the throttle lever attachment is directly to the IP. the early IP is unique among diesels and looks like a cylinder with the plunger, throttle lever and fuel feed sticking out in various directions.

the YSE/YSB pump:



the YSM has a Bosch-style variable displacement type pump, much more complicated with an internal governor linkage. this one looks like most other diesel injectors, it has a more streamlined casting with three prominent mounting bolts around the delivery valve.

the YSM pump:





> Does anyone have experience with installing a Sunity IP or finding a replacement Yanmar IP?

i put a Sunity IP on my YSB last year and have been happy with it so far. i don't believe they make a YSM pump, and unfortunately they advertise their early pump as suitable for the YSM — but it's not =(

[HorseshoeBay]

Will try to find spare parts, such as the barrel and plunger.

[HorseshoeBay]

Barrel and plunger part numbers

[HorseshoeBay]

Hopefully, after 2 hours of close inspection and slow fine sanding the injection plunger and barrel and sufficiently lapped.

[HorseshoeBay]

To polish the plunger, I wrapped the reverse side of fine sand paper anround the plunger and rotated it until a polished finish was achieved.

The Yanmar manual includes tests of the injection pump plunger and barrel and check valve assembly.

Not having specialised equipment, to check for air tightness a breath pressure test was conducted:

Inserted the plunger, covered the side hole, held the end of the plunger and blew into the barrel as hard as possible - no leaking was detected (a bubble in water test could be done).

The Check Valve test was passed.