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Old 02-12-2020, 19:40   #1
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Join Date: Dec 2015
Location: Chesapeake Bay
Boat: Beneteau 445
Posts: 47
Injection pump leak

I noticed a small diesel leak in my trusted Yanmar 4JH2E that I traced to the top injection pump (see pic). Looking at the service manual it shows an o-ring in the delivery valve that I think it might be the problem. So I am planning to order the o-ring and replace the four of them myself. I've never removed the delivery valve from an injection pump, anything I should be aware of? I see some spings in there. Should I be worried of pieces flying all over when I remove it? Any tips are appreciated.
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Old 02-12-2020, 22:18   #2
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Join Date: Sep 2014
Location: Auckland, NZ
Boat: Compass 790 , 7.9 metres or 26 ft
Posts: 2,417
Re: Injection pump leak

If its the same setup as the Bosch/Zexel PFR on our Yanmar ( it looks the same) there is nothing to be frightened of. There is a spring there but it wont shoot out but I havent got the service manual for your engine so maybe wait till someone with your engine chimes in. That spring sits on top of the delivery valve.
Always best to return the parts to the holes they came out of. There should be a torque setting for those delivery valve holders in the manual.
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Old 03-12-2020, 07:33   #3
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Join Date: Feb 2012
Location: Carrabelle, Florida
Boat: Fiberglas shattering 44' steel trawler
Posts: 3,517
Re: Injection pump leak

Consider purchase of an o-ring kit. It will get you out of all sorts of problems on a boat, and cost little more than ordering one o-ring from Yanmar.

I can't speak to your particular engine, but I recognize that Compass790 speaks with wisdom. It's not rocket science, and a bit of exploration on your part will pay off in understanding your engine. Just remember that you are dealing with high pressure components, so the cleanliness and assembly standards are higher than for ordinary mechanical repairs. Be careful to learn/record the order of re-assembly as you take it apart, and safely store each little gismo as it comes off, rather than having to search for it in the bilge. At the very worst, and it won't happen, you might end up needing a more experienced mechanic to put it back together correctly.
Never let anything mechanical know that you are in a hurry.
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