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Old 09-08-2020, 15:10   #1
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Yanmar 4JH series injectors

Working on pulling my injectors out of 4JH. Been two days now... they’re in there good.
Question 1- Assuming everything was relatively newly installed , etc, the injectors shoould be able to be pulled straight out? They aren’t a quarter turn or anything?
Question 2- Several places online have suggested securing fuel to engine and just cycling start a few times to pop injector out. That sounds like a bad idea to me. Especially because mines REALLY stuck in there.
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Old 09-08-2020, 16:17   #2
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Re: Yanmar 4JH series injectors

I’ve had my injectors out, 4JH4, when engine had about 800 hours. They came right out. Just unscrewed IIRC, been 10 years.
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Old 09-08-2020, 16:22   #3
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Re: Yanmar 4JH series injectors

Mine came out easily too. Been a few years but I don’t remember them being screwed in?
Held in by two nuts? Anyway spray some penetrating fluid around the body of the injector and let it sit overnight, then with the nuts loose but not removed spin the motor over with the fuel lines disconnected so it can’t start and use compression to push them out.

If that doesn’t work reconnect fuel lines and crank it up and let it warm up, then repeat with a warm engine.

Mine is a 4JHE
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Old 09-08-2020, 16:30   #4
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Re: Yanmar 4JH series injectors

I don't have a 4JH manual however the injectors of Yanmar engines of similar vintage are pulled straight out. The 4JH2 injectors are pulled straight out.

A slide hammer secured into the top of the injector helps or you can make jig to push them out using the clamp studs (modified).

If you wish to read about really stuck Yanmar injectors, have a look at this thread
https://www.cruisersforum.com/forums...ve-210170.html
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Old 09-08-2020, 16:31   #5
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Re: Yanmar 4JH series injectors

Quote:
Originally Posted by Jotunheim View Post
Working on pulling my injectors out of 4JH. Been two days now... they’re in there good.
Question 1- Assuming everything was relatively newly installed , etc, the injectors shoould be able to be pulled straight out? They aren’t a quarter turn or anything?
Question 2- Several places online have suggested securing fuel to engine and just cycling start a few times to pop injector out. That sounds like a bad idea to me. Especially because mines REALLY stuck in there.
I believe that the 3JH injectors I have are similar. Had to remove one of mine (two times, different ones) and they did not want to come out.

The fuel line is already off, removed the nuts, covered with a heavy towel, cranked the engine (with engine stop lever engaged), and they blew out handily. Next time I put them in with anti seize, but I doubt if that would help.
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Old 10-08-2020, 06:49   #6
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Re: Yanmar 4JH series injectors

Quote:
Originally Posted by Jotunheim View Post
Working on pulling my injectors out of 4JH. Been two days now... they’re in there good.
Question 1- Assuming everything was relatively newly installed , etc, the injectors shoould be able to be pulled straight out? They aren’t a quarter turn or anything?
Question 2- Several places online have suggested securing fuel to engine and just cycling start a few times to pop injector out. That sounds like a bad idea to me. Especially because mines REALLY stuck in there.


leave your engine to be room temperature , spray WD-40 , start your engine and let at idle for 5 minutes , only 5 minutes not more and let it overnight .
. The cylinder head is aluminum the injectors steel they have different expansion ratio . the aluminum will expand quicker.
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Old 10-08-2020, 11:40   #7
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Re: Yanmar 4JH series injectors

Quote:
Originally Posted by MARINE ENGINNER View Post
leave your engine to be room temperature , spray WD-40 , start your engine and let at idle for 5 minutes , only 5 minutes not more and let it overnight .
. The cylinder head is aluminum the injectors steel they have different expansion ratio . the aluminum will expand quicker.
Aluminum??? My 4JH3 is cast iron. I don't recall a diesel with an aluminum head.
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Old 10-08-2020, 15:39   #8
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Re: Yanmar 4JH series injectors

All Yanmar diesels of this vintage are cast iron!
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Old 10-08-2020, 15:59   #9
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Re: Yanmar 4JH series injectors

Aluminum diesel cylinder heads are very rare, they do exist.
In 2001 when I bought my Duramax engine powered truck there were many, many experts that said they would never work as the Duramax has an aluminum head, there were many predictions of cylinder head gaskets failing etc.
Properly designed aluminum works fine for a diesel cylinder head, but I believe in the US consumer market the Duramax in 2001 was about the first.

However aluminum Diesels are far from new, the Soviet T-34 tank had an aluminum engine that was astonishingly very advanced. Double overhead cams per head and a four valve head and all aluminum, I believe the -34 in the name comes from it’s design date, so a four overhead cam, four valves per cylinder all aluminum V12 Diesel engine in 1934.
From the Russians who anyone will tell you were only capable of manufacturing crude junk.
https://www.cia.gov/library/readingr...00070001-4.pdf
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Old 10-08-2020, 19:30   #10
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Re: Yanmar 4JH series injectors

I'd try penetrating oil & slide hammer.
Try twisting it as well using a spanner or pipe wrench if you can fit it on. If it is really badly stuck you can dismantle the top off the injector & make up a socket to fit on the flats & hit it with a rattle gun. I would put a bit of threaded rod in the threads in the body by the flats so it doesnt distort if you wish to save the injector . Or try freezing spray.
Refer to Wotnames thread if none of these suggestions work
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Old 17-08-2020, 13:02   #11
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Re: Yanmar 4JH series injectors

I had a similar problem with one injector on my 4jh2. I was able to remove the injector by first removing the small stud that is in the way, then using a crow's foot wrench to twist the injector. If the seat doesn't come out with the injector, a bolt extractor will break it free.
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