Hello,
Here’s an update.
My truck has been checked by two mechanics, one of whom previously worked for ISUZU. As we had all diagnosed, it really is a timing issue.
My injection pump needs to be set at 8 degrees and not 6 degrees before TDC (it’s even written on a sticker inside the cab).
After many hours of inspections, the mechanics couldn’t find the source of the problem — every component works perfectly on its own, but together, it’s a disaster.
They came to the same conclusion as I did, even though they had never seen this before: the issue might be with the double gear or the crankshaft gear.
I had no choice but to pull the engine out and start dismantling it until I could access this double gear.
I took it apart and removed the ring using a press… but it wasn’t the culprit — it’s a single-piece part.

That leaves as the main suspect the crankshaft gear, which is press-fitted and keyed, and might have slipped by breaking the key — my “klac” sound.
Except I don’t have the proper tool to remove it. I tried as hard as I could, using every method possible to get it to move, but it wouldn’t budge.
I gave up, especially since I think I damaged some teeth and bent other gears while forcing it.
In the meantime, I found a used engine that could be a match.
Mine is a 2003 4HE1-XN, and the other one is a 2006 4HE1-XS.
To make it compatible, I had to remove the EGR, block a hole near the intake, install my new turbo, my alternator, my power steering pump, and of course modify/reuse some water/oil hoses.
I lined the engine up with the gearbox, but they wouldn’t mate. I took it back out and realized it didn’t have the same clutch or the same number of teeth.
So I had to change the clutch and the flywheel, which didn’t have the same dimensions.
I reassembled everything, changed the fluids, bled the system, and turned the key… it started instantly — and without smoke!!!
Just a little blue smoke, but considering it has 250,000 km, that’s normal, I’d say. And nothing compared to my first engine.
For reference, this 4HE1-XS has its pump set to 9 degrees before TDC.
If I find the courage, I’ll cut off the crankshaft gear to see if its key is broken, just to confirm if it was indeed the culprit.
I also need to recover my new cylinder head and all the parts that could be useful to me.
I’ll keep you updated.
See you soon.