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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
Didnt really feel like buying the amp clamp to check timing so I pulled the timing cover this morning. Much to my surprise, the engine is in time. Chain has a lot of slop in my opinion so I'll be replacing the timing set before we go back together. Also two pretty good grooves worn into the little rubber timing damper.
I've been timing the cmp off the wrong mark according to what I saw with the sprockets lined up - I've been using the last big mark that lines up with 0 but it's actually the small one part that. Whoops. Doubt that's the reason for no-start and I probably adjusted enough to make up for it using the o-scope the other night. I would have noticed the misalignment probably.
harmonic balancer seems to still be in line and everything but since rubber is cracked and it's off, I'll get one of those too...
I guess I'll see about testing injectors while the engine is apart waiting on parts. Got to be getting closer to a solution.
Kinda disturbing thought I had today - maybe this is just straight up the wrong engine. It has 48 link timing chain, a knock sensor, and had the wrong flexplate, what if this isn't a 98 engine at all? So the issue for me is if it's the wrong cam then how could I make it work at all? Maybe that's the problem?
is there a good way to ID the engine year other than what I've already provided?
Passenger side near the distributor. Up and a bit to the right. Engine date code.
4.0 Engine date codes
The date code is on the passenger side of the engine, on the block, just forward and up from the distributor on a machined flat surface.
The digits of the code identify:
1st Digit-The year (8 = 1998).
2nd & 3rd Digits-The month (01 - 12).
4th & 5th Digits-The engine type/fuel system/compression ratio (MX = A 4.0 Liter (242 CID) 8.7:1 compression ratio engine with a multi-point fuel injection system).
6th & 7th Digits-The day of engine build (01 - 31).
FOR EXAMPLE: Code * 801MX12 * identifies a 4.0 Liter (242 CID) engine with a multi-point fuel injection system, 8.7:1 compression ratio and built on January 12, 1998.
Phew - confirmed 98 donor engine (October 97). Thanks for that, Dave. So the only differences in timing and cam between this engine and my original one were the cam retention, no re grind or change in timing... guess I'll order the updated timing set for a 1998 and get that installed, hoping it solves all the world's problems.
got the new timing set installed yesterday. She's still a no start, not terribly surprised since the timing chain wasn't absolutely hosed just worn. Went ahead and checked compression and unsurprisingly it was low (cylinder wash from the bad flex plate/overfueling, a couple cylinders read 60 and some more like 90) so I put some pb blaster in the plug holes and turned it around a few times before purging with the starter and reinstalling plugs. Still no start, popping out both ends like before. The rings don't squeak any more which is cool but a couple cylinders are giving me like 88psi ish even with the residual pb blaster in the cylinders and a couple more like 120-30. Anyway it should start with that much compression even if it wouldn't run great.
I did replace a broken vacuum elbow on the intake last night, might just start doing some general stuff like that and see because she's close. But at the same time the timing still kinda seems bad because it is backfiring out intake. If i floor it it will pop out exhaust.
My current line of reasoning is this: based on the amount of fuel this thing ran through it while the bad flexplate was installed, and the fact that it slayed a fuel sender during that time etc, perhaps there's some injector issues now too. I know they ohmed out fine but perhaps they're leaking or not atomizing fuel properly and that's what's causing troubles, since the popping changes with the throttle floored. Or it could be AIC related possibly, based on that theory. Honestly I dont get the popping out intake seeing as I've now verified every bit of timing-related componentry on the rig...
I guess I can backprobe the injectors while cranking and see where they're going off an on especially relative to spark. So I'll do ckps plug wire 1 and injector 1 on my scope, see how that all lines up and I guess continue down the line and see.
05-14-2022, 01:17 PM
