4JG2 conversion - very hard cold start, smokes on cold start

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4JG2 conversion - very hard cold start, smokes on cold start

Postby rmfurr » Wed Apr 26, 2017 10:02 am

So I just had my friend do a 4JG2 manual conversion on a 2001 Trooper. Finally got my hands on it after months of waiting.

The thing starts and runs fine once warmed up, but very hard to start when cold(and outdoor temp last couple days is low of 39F with high of 60F) and smokes(mostly white it seems) quite a bit until it warms up and then doesn't smoke at all.

My friend just changed the glow plugs thinking that could be the issue, but it doesn't seem to be helping. Yesterday my friend got it going with 2-20 second cycles of glow plugs plus a few 10+ second cranks. Today I can't get it started at all.

Any idea what could be going on here?

What is the normal length of time to run the glow plugs? I want to try leaving them on longer but don't want to burn them out.

Any possible solutions to this you guys see?
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Re: 4JG2 conversion - very hard cold start, smokes on cold s

Postby mudoilngears » Wed Apr 26, 2017 10:34 am

I would suspect injectors, do you have a diesel place near you that can check pop pressure and spray pattern?
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Re: 4JG2 conversion - very hard cold start, smokes on cold s

Postby mudoilngears » Wed Apr 26, 2017 10:41 am

And 20 seconds on chinese glow plugs is pushing it I'd say. I'm asking a mechanic friend that has a lot of experience with Diesel Isuzu's
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Re: 4JG2 conversion - very hard cold start, smokes on cold s

Postby mudoilngears » Wed Apr 26, 2017 11:23 am

Ok, so I talked to someone who knows. He says he suspects injector pump timing. Did your friend change the timing belt? If the timing is right he says the advance mechanism inside the pump may be stuck either on advance, or retard, thus throwing your timing off. He says to play with the pump timing a bit to see if it helps.
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Re: 4JG2 conversion - very hard cold start, smokes on cold s

Postby rmfurr » Wed Apr 26, 2017 11:28 am

Thank you very much for your help! Yes, my friend did change the timing belt. Is that a simple thing to check/fix?
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Re: 4JG2 conversion - very hard cold start, smokes on cold s

Postby mudoilngears » Wed Apr 26, 2017 11:29 am

rmfurr wrote:Thank you very much for your help! Yes, my friend did change the timing belt. Is that a simple thing to check/fix?


I would suspect maybe he got the pump timing a tooth off. It's not really complicated. Just take the front plastic covers off and check the timing marks.
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Re: 4JG2 conversion - very hard cold start, smokes on cold s

Postby onebadtrooper » Thu Apr 27, 2017 12:07 pm

Check your return line from the injectors, Mine had a small hole which I believe led me to loose a prime to the injectors. Mine had the exact symptoms you describe. ALOT! of white smoke, once I repaired the return line and primed the system all is good now....
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Re: 4JG2 conversion - very hard cold start, smokes on cold s

Postby rmfurr » Thu Apr 27, 2017 8:04 pm

onebadtrooper wrote:Check your return line from the injectors, Mine had a small hole which I believe led me to loose a prime to the injectors. Mine had the exact symptoms you describe. ALOT! of white smoke, once I repaired the return line and primed the system all is good now....


Thank you! I will check on all this soon! I hope I can get this baby going.
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Re: 4JG2 conversion - very hard cold start, smokes on cold s

Postby rmfurr » Sun Apr 30, 2017 8:24 pm

So I haven't been able to get anyone to check the timing yet, but my friend assures me he checked it 3 times.

Some other issues. The smoke coming out at the initial start(first 3 minutes( seems to be blueish white, not just white. Also there seems to be a slight oil leak down the side of the engine and a tiny ammount of oil comes out of the tail pipe. Runs seemingly find when at temperature, however the smoke also comes out heavy when accelerating, mostly white blue but a half second puff of black smoke)

Does this give any more clues?
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Re: 4JG2 conversion - very hard cold start, smokes on cold s

Postby 96TrooperSE » Mon May 01, 2017 12:22 pm

Blue smoke would be burnt oil. I would guess your tubo seals are leaking if you're getting oil out the exhaust. Probably not related to your cold start symptoms.

I also have similar issues with white smoke and missing on startup. It goes away much faster if I just drive it and get in the throttle versus idling. I've checked the timing 4 times and redid all the fuel lines using clear lines on the supply and return for the pump to monitor for air bubbles (none). I think mine is more a injector pump issue because if I advance it to the max it runs better, still smokes but starts smoother with less missing. I'm thinking the cold start advance is not working

I'd recommend getting an exhaust gas temp gauge if you're going to be playing with the timing.
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Re: 4JG2 conversion - very hard cold start, smokes on cold s

Postby rmfurr » Wed May 10, 2017 7:53 pm

Just did a compression test.
Here are the results:
1: 340
2: 340
3: 340
4: 260

Doesn't seem like good news. What does this mean for me?
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Re: 4JG2 conversion - very hard cold start, smokes on cold s

Postby onebadtrooper » Thu May 11, 2017 12:03 pm

I would do a valve adjustment and check again.
89 trooper, 6"lift, 35x13.50R15 baja claws, tera low 3.07's and 5.38's.custom bumper F&R, built 3.4L,safari snorkel.

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Re: 4JG2 conversion - very hard cold start, smokes on cold s

Postby mudoilngears » Thu May 11, 2017 12:21 pm

onebadtrooper wrote:I would do a valve adjustment and check again.

That was my thought too, a valve could be a tiny bit tight and cause a compression leak.
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