broken Flywheel question/ cranks No start long

Ok so a couple months ago my DD 2000 Xj 4.0 AW4(<160,000 on the clock) started having a problem running. It would Start up run for a bit and then die. So I plugged in my cheap code reader and start chasing my tail. Codes and follow on crap sort of went like this.

1st code P1391-so get a new CKPS and an IAC / swapped em in. No change
Then code PO351 and PO352. Installed a new napa iginition rail and plugs. Still no change

It still fired up, runs for a few seconds and dies. This continued for a couple days. I finally decided somone other then me needed to fix it. So it ended up at a friend of my dads shop for 4 days. They cant figure it out (so no charge) and tell me to take it to the dealer cuz they think the PCM is bad.

3 hrs at the local dealer and I am out 400 bucks for a Diagnosis and a new cam position sensor (which they said was open so they installed a new one). This did not fix the problem and now it wont even run. They (dealer) say the motor "sounds blown".

So I take it home and yank the motor out, figuring to swap it for my old 92 MJ 4.0. Got it out and found that the flywheel had sheared from the crank leaving its center section attached to the crank, but otherwise completely seperated from the crank.

So I source a new (used) flywheel from an late model xj. My old trans smells burnt and had overheating issues so since its all out on the garage floor anyway I decide to get a low mileage replacement with a TC. I also decide while its out now would be a good time to replace gaskets on the motor, so a full gasket kit gets done too.

Swaped the whole kit, 4.0- trans and t-case back in the other day, plugged everything up and tried to fire it up. For some reason it wont fire up.

It cranks , but wont run. So I pull the timing cover to ensure the timing marks line up still. TDC on cylinder one and the crank and cam pully marks point right at each other. Chain appears good. Reassemble and try firing still no fire. But if i crank it long enough it backfires out the tailpipe.

So now I am grasping at straws.

? when installing the flywheel does it get keyed in relation to the block somehow? Is it possible the the orientation of the flywheel when being mounted would affect timing in a drastic manor?

As of today it has new
02 sensors
coil pac
plugs
flywheel
torque convertor and trans
IAC
Crank pos sensor
Cam position sensor (installed by dealer prior to discovery of broken flywheel)
and a complete motor gasket kit.
New fuel pump.

i have 12 volts at the battery and at all grounds. Judging from the back fire I have spark, and at the fuel rail I have enough pressure that if I detent the check valve it sprays all the way to the fender.

HELP?

You got the right flexplate (not called flywheel on an auto) on there? The older Renix flexplate will not work right with the newer computer as the slots are spaced differently. It might give you spark/fuel and maybe fire, but it'll run like crap.

Have you tried some things like a noid light to see if injectors are getting firing signals to open the injectors. Checked for actual spark with a used spark plug in one of the SP wires and the body of the plug grounded?

I had a no start problem that drove me nuts that turned out to be an air intake temp sensor that was off. I would suggest getting a volt-ohm meter busy checking for room temp spec values on the MAT and CTS for starters.

Can't really help on the flywheel question, but it is a good question to ask!

At some point I would try and find a loaner PCM to test. Check the PCM feed voltage the sensors, like the TPS, CTS amd MAT amd MAP.

MAKE SURE that's the right flexplate. there are differences in notch spacing on some years, the crank sensor won't have any idea what to do with the wrong spacing.

lawsoncl said:

You got the right flexplate (not called flywheel on an auto) on there? The older Renix flexplate will not work right with the newer computer as the slots are spaced differently. It might give you spark/fuel and maybe fire, but it'll run like crap.

Click to expand...

I get the flexplate & flywheel terminolgy screwed up all the time too. I was interogatinmg 5-90 the other day about the flexplates, asking if they can be rotated to get around high wear on the teeth from starter munching, and we never quite figured out the answer. I suspect it can be installed in 2 positions, one write and one wrong, unless there is a locator pin to make it a one way deal. But I have not personally had my hands one yet during assembly. I am told there is a 4 bolt and six bolt pattern, 6 bolts the crank and 4 to the TC, so that only leaves 2 possible ways to line all the bolts up properly, but one way would be wrong as it would throw the 3 location slots for TDC reading by the CPS (CKP) off.

OMG, he did swap a 92 into a 2000. He probably replaced the 92 FP with 92 FP, not a 2000 FP. So who knows if the 92, OBD-I was different from the 2000 OBD-II FP?

The bolt holes are unevenly spaced. Without removing some metal, there should be only one way to install it. Make sure it is the correct flex plate ie. Renix vs HO.

Check your distributor indexing.

Ecomike said:

OMG, he did swap a 92 into a 2000. He probably replaced the 92 FP with 92 FP, not a 2000 FP. So who knows if the 92, OBD-I was different from the 2000 OBD-II FP?

Click to expand...

He didn't really say that. It's not really clear. He planned to swap it, but when pulling a motor (the 2000?), he discovered the broken flexplate. He also lists work done as a coil rail which would be irrelevant is he swapped the motors completely. The question of the correct flexplate notches is of course completely relevant. It also seems like the broken one would destroy the original CKP, but hopefully he replaced that.

Hey guys, thanks for the input. Sorry for the vague info, I was trying to keep it as short as possible. The 92 and 94 4.0's with a manual flywheels are still sitting on the ground in my pops garage waiting to be stroked along with the 258 crank and rods. Just a job/money issue right now.

I was told the used flexplate (I stand corrected) that I purchased was from a late model xj, I will reconfirm that asap.

When installing it I did notice that the bolts only lined up one way or so it seemed at the time. I guess I should have asked if it was possible to install it rotated 180' degrees?

Ecomike, If I was even remotely confident in my ability to handle all those electronic checks I would. But I'll have to take a course in terminology before I would even begin to understand what I am looking at. I took your advice regarding a PCM switch a couple weeks ago after I got the jeep back from the dealer and before I discovered the broken flexplate. I will try that again though.

Oldman, I have that distributorless set up on my heep. My searching here last night prior to posting netted me an article someone here posted regarding indexing the distributor set up on my jeep w/ a toothpick. I intend to attempt that tomorrow night.

Winterbeater , I am one of those Rochester pricks that lives north of you by a couple minutes, feel free to hit me up for an addy and I will let you come have a listen before I tear her apart again.

Thanks again gent's.

RLTW,
Grifter

also sorry if my responses are slow, I dont have I-net at my house so I am only on when I am over here at mom and dads wrenching and running into problems..... like now.

Put a timing light on it to see if it fires steadily at the right time.

Ok I finally got a answer from the guy that sold me the flexplate.. its from a 98 so it should be the right flexplate for my 2000 right?

My wifes mom and s-dad decided to drop in from out of town on tuesday so I had to put the heep on the back burner. Hopefully I will swing a couple of free hours out of the upcoming school week to pursue whatever is causing this thing not to crank.

thanks,

Grifter

back at it today,

someone here want to explain to me how I am supposed to check for spark on this distributor-less system. I can do it on the old school set up, but I am baffled as to how I am supposed to get around this coil rail?

Thanks,
RLTW,
Grifter

I have not seen them. Is there no secondary wire to the spark plugs that you can pull?

Is there room for an old style dwell meter pick up sensor to wrap around the inductor wire?

91-2000 has the same flexplate and it can only go on one way.

Here is a good article on indexing your cam sensor:

http://motorage.search-autoparts.co...estandard//motorage/292005/169830/article.pdf

Ecomike: I think I got it figured out. It looks like I have to pull the entire rail and the plugs. Unlpug it and then "reinstall" the entire rail in a laying position on top of the vavle cover. Insert plugs (1x1) and attempt to fire. As of now I am waiting on another pair of hands to arrive to crank the motor.

Tayln: my searching a couple days ago netted me that very same article. I have a printed copy of it permanently attached to my FSM along with a old post made by OLD Man that lists all the check one must go thru to diagnosis a "cranks, No start" condition (although IU dont think I could find that here again if I tried). I intend to tackel both of those today. Thanks though. The more places that link is posted the better.

Ok so here it goes. Just did my check for spark. As far as I can tell I am getting intermitent weak spark in a couple of select plugs( namely #2, #3, #4 cylinders fire) #1 and #6 do not appear to fire. I am about to swap the old coil rail back in and see if that changes this issue. still odd though I thought the heep should run with a couple of cylinders down.

Idle can be real rough with 2 down, 3 down may be a killer.

Did you provide a way to ground the plugs when you tested the rail?

you know what come to think of it.. I had just pressed the bodies of the spark plugs against the valve cover. Completely didnt occur to me that there is a gasket, and some crommets that install in the cover in relation to the bolts that keep the actual cover from making solid metal to metal contact anywhere. damn I feel stupid. I'll screw with it tomorrow.

thanks,
RLTW,
Grifter