About a month ago, I tore into an Isuzu NPR with the 4HK1, that had overheating issues and ruined the head-gasket. Work sent the head to the machine shop and their verdict was: "This head is a banana. Beyond economic repair."
So work went and ordered a replacement head, and it turned out to be coming from Japan. We stuff the truck round the back of the workshop and forget about it.
A month later, the head has arrived and had various parts transferred over by whoever it was work ordered it from; who also advises that the cam sensor retaining bolt is a different size, but the sensor bore is the same so they can just redrill it for the old bolt and we can fit the old sensor.
(Red flag!)
Anyway, we get the head in, and I start the painful process of building the engine back up. Tucked in the back of the head is a piece of cardboard with the word "Loose" written on it (Rood! That's none of your business! :I ) because without the head being in the engine they have no good way to hold the timing idler gear to tighten the bolt. So once I get all the valvetrain together, with the valve adjustment slackened right off, I go to bar the engine over.
It won't turn. Panik!
Undo all the bolts holding the rocker shaft down, cam-caps, etc. Still won't turn. Ends up being the idler gear locking up when I tighten it. Turns out they fitted it backwards when they transferred it over.
No biggie, take the rocker assembly and camshaft back out, take the idler gear out, reassemble it all correctly. Engine now bars over lovely!
Reassembly resumes, and I finish the day on Friday with only a few hours' rebuilding remaining. Saturday morning, I finish up assembly, get all the accessories fitted (including the stupid fridge box pump and its bracket), and we fill all the fluids.
Turn the key, engine cranks! and cranks, and cranks, and cranks.
Boss is, at this point, in full Spanish Inquisition mode, and basically accusing me of not getting the timing right; I assure him it's correct, etc.
So out comes the easy-start. He loves that stuff.
And we prove the engine runs with that, so the valve timing is correct, but it just. won't. start.
At about half eleven, I break out the diagnostic laptop. It plain as day tells me: "no pulses from the cam sensor"
Check the plug: it's fine
Take the sensor out: it's f....ucked. The whole end is missing.
Boss goes thermonuclear. We drain the coolant, pull the EGR cooler off, open the engine up. Sure enough there's plastic sensor shrapnel everywhere; so we pick as much of that out as we can. Cue more wild-ass accusations from the boss man. ("it must be when that gear was backwards" no, that gear's too far away from that, to do that. "Well what do you think it is then?!" Gee, could it be that the new head takes a different shorter sensor?)
Anyway, today we went and robbed its sister truck from the customer, I pulled the cam sensor out of that, and put it in the hole while one of the cam sensor teeth was lined up with the hole, and sure enough: the sensor hits it before it goes all the way in the hole.
The new head for the engine is machined differently and puts the cam sensor 5mm deeper into the head! And I had the bad luck that the tooth was clear of the sensor when I fitted the sensor, then when we cranked the engine it just smashed it all tae fuck.
Moral of the story: If the mounting hole is in a different place, maybe there's a reason and maybe it takes a different sensor.