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4jg2 knock under load

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4jg2 knock under load

Postby RyanE123 » Sat Oct 02, 2021 10:19 am

long story short i bought a trooper, engine needed new seals in fuel pump, done that and then once turning on, engine would rev through the roof and want to keep going. Couldn't be assed fixing this so i took my belt gear off another engine that was in good working condition and converted engine to belt drive from gear drive. Using the fuel pump, injectors, cambelt and backing plate, new water pump and belt and new glow plugs
engine started up like they should, took it for its first drive and under load it had a knock. Only on load.

got a engine rebuilt with rebuilt injector pump rebuilt injectors and dropped that into the trooper.
Same knock is there.

I have pulled engine and checked bearings checked oil filter, no metal shavings and clearances come out fine.
played around with the advance on pump and I'm sitting at 0.57 slight advance usually I'm above 0.6
also no exhaust leaks and exhaust shrouds are tight.

I have used the screw driver to ear trick to try and find the knock also bought a mechanics stethoscope to prod around and listen for the knock.
No matter where i poke it I can hear the knock.

First I thought the issue was diesel rattle but with a rebuilt pump and injectors I'm starting to believe it's not, I know bottom end could be an issue but I have triple checked bearings and can almost cancel that out since I have had two different engines in the vehicle and both have had the same issue. The only thing that is the same on both engines is the cambelt, tensioner bearing, backing plate and waterpump.

Fuel has been drained out of tank and a tank full of new fuel has been added.
Noise is there if clutch is engaged or not.

Has anyone had an issue like this before or can lead me in the right direction?

I have timed pumps before and not had issues, Only difference is I have used my own dti gauge this time rather than a mates one, dti gauge is new and I can't confirm the accuracy. Wouldn't think it could be that though.
RyanE123
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Re: 4jg2 knock under load

Postby geeves » Sat Oct 02, 2021 2:33 pm

could still be a timing issue
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: 4jg2 knock under load

Postby RyanE123 » Sat Oct 02, 2021 3:06 pm

It definitely sounds like a timing issue to me and a few others. I just don't know how to confirm it without a gauge, only other way I can think of is to time it by ear rather than by gauge.
RyanE123
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Country: New Zealand
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Isuzu Trooper 3.1

Re: 4jg2 knock under load

Postby RyanE123 » Sat Oct 02, 2021 3:21 pm

Link to video if anyone is interested https://www.youtube.com/shorts/XoiRuBBLE6A
RyanE123
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Posts: 10
Joined: Thu Jan 07, 2021 12:35 pm
Age: 26
Country: New Zealand
City: Napier
Vehicle: Isuzu Mu 3.1
Isuzu Trooper 3.1


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