ChoppedLaredo

So I swapped a 91 4.0 into my 1990 laredo.
changed over all brackets, pulleys, wp, intake/exhaust.
only thing different was that new block did not have the coolant sensor or knock sensor(i think) but i dont think that this would cause a no spark.
i also changed over the distributor. i think i might not have indexed it properly, but i am damn sure i did.
the old engine fired up, with a busted rod, prior to removal.

so what wth could it be?
i played with the cps and harness, still no luck.

i found these articles, i think i am going to saw off the notch on the distributor and see if i cant get a spark then.

http://ezinearticles.com/?How-to-Ind...tor&id=1357018
http://www.asashop.org/autoinc/feb99/techtotech.htm
http://www.angelfire.com/my/fan/dist_index.html

ChoppedLaredo

please help, i am getting no spark
any suggestions.

troy fritz

I put a 98 into my 96 and had same problem. My distributor was 180 degrees out . Runs great now. Pull it out and turn it half turn then try it . Hope this helps.

91familyxj

Do you have power at the coil? I dont think being 180 out wouls be the problem because he has no spark at all. I wouls try the other dist.

ChoppedLaredo

hey guys i had the ignition control module checked, ok, had the coil checked, ok.

the only other thing i can think of is the crank sesor, ohms read ok, but you never know. tommorrow i am checking harness ,and ecu reading.

also i found this: considering the motor in my jeep was laying in a yard, rust might have accumulated on flywheel dish where crank sensor picks up signal,

jeepkingxj from ilovejeep.com forum
you might want to try to scrape/clean the flywheel(flexplate). I had this problem with a few xj's. changing the cps won't make a difference if the flywheel is rusty/dirty, because the cps is magnetic and needs to read the metal spaces. rust and dirt will make it hard to read. you can try cleaning it through the cps hole, using a small wire brush and some wd-40/pbblaster. Disconnect the fuel pump relay or unplug the coil battery source. while having someone cranking the engine place a slender wire brush against the flywheel. crank/brush for 15 seconds then spray with wd-40/pbblaster. you may have to do this a few times untill shiny. then reinstall cps and fuel pump relay/coil plug and start. you can also remove the trans and polish the flywheel. these things work just like a lawn mower if you leave them in the weather they rust and won't start.

soooo, ill check out the flexplate tommorrow, clean it up abit, like i said, the car was running, i swapped block, head, and flywheel/flexplate, no more spark.

what do you guys think?

91familyxj

Well everything is worth a shot and if it is something you can do for free why not. Let us know what happens

Abovetimberline

Is the flexplate from the 90 or 91?

ChoppedLaredo

91 i believe, my jeep is a 90, new motor is from a 91(this coming from the hillbilly that sold it to me)

Are you trying to tell my that im going to have to change that thing? Oh no

kept the flexplate that was on new engine sold to me, so yeah i think it its from a 91,

Abovetimberline

if it already had a flexplate on it then it is a 91 and will not work with your 90 renix system,the tone ring on the 91 is alot different and your cps and pcm do not see it.
You need to use the flexplate from the 90.
There is one thing to remember,in 91 chrysler made alot of changes to the operating system and is the first year that they actually made the xj,so there were changes from the renix operating system.
The only thing you can use from the 91 is the longblock without modifying alot,you need to use the flexplate,intake,exhaust manifold,dist,etc, from the 90.

ChoppedLaredo

Do you mean im going to have to tear that thing apart again!!!!!
Than you good sir, you saved me a lot of time, I will take down the transmission tommorrow, or begin to.... then change the flexplate.

Does it have to be inserted a specific way? i noticed the notches on my 90'. does it have to be in sync with the cam sensor?

Ill be here all night, english 102.

Abovetimberline

Yes if the flexplate is a 91 then you need to install the 90.
The flexplate will only go on one way,make sure you torgue it down to spec which is 140ftlbs,you will need some help to hold the engine from turning when you torgue it down,I use an impact to take them off.
Before you install the 90,check it for cracks around the center and bolts,common problem.

ChoppedLaredo

Yeah i dont think i want to take out that I6 again. so i will remove the tranny, 4wd, oh man!( anything i should replace while i am in there? I already replaced the tranny seal or torque converter seal.) I will replace the rear tranny seal, if there is one maybe thats where I am leaking. Also tranny mount, that thing looks like the hunchback of notre dame.

The flexplate fits only one way, so i do not have to worry about adjusting it to tdc or to the distributor? ok then,

Thank you. I ll keep you updated. I strongly believe that this will solve my no spark problem.

Abovetimberline

As long as everything else is good with the motor it will run fine,just some advise a trany jack will make it much easier to remove and reinstall,I would defintley install a new trany mount,I would replace all your xfercase seals,just take your time and inspect everything.
One more thing when removing the trany disconnect all your linkages and wires and lower the trany down in the back and let the motor come down with it,this will make it much easier to get to the the top bolts on the trany,the motor mounts can handle it,then jack it back up and remove the lower ones,makes getting the top ones much easier.
Be careful not to rip your cps wires out,it happens alot when removing the trany.

jarretthise

Idk about the earlier years but I know that the later year Cherokees use a reverse torques head bolts on the upper bellhousing bolts. I would replace them with reg hex head bolts. Just to make things easier down the road if you ever have to do anything again.

ChoppedLaredo

Thanks guys, it was the flex plate, I removed the tranny, and yes the flexplates are different. The Jeep started right up! its smoking some black smoke, but ill check that out later, I have to replace a clip that broke off one of the tranny lines, found it at AA. Vacume line Diagram Anione?