Firing order

[NCSUcherokee]

Today i got around to switching out the CPS, with mixed results.

With the replacement CPS, the engine idled alot smoother, and i was able to nurse it off idle up to about 1k but not any further. BUT now it is much much harder to get it started. It starts to sputter and kick after 2 cranks but had a hard time catching fire. By the end of the day, i couldnt get it to start at all.

 

[langer1]

Today i got around to switching out the CPS, with mixed results.

With the replacement CPS, the engine idled alot smoother, and i was able to nurse it off idle up to about 1k but not any further. BUT now it is much much harder to get it started. It starts to sputter and kick after 2 cranks but had a hard time catching fire. By the end of the day, i couldnt get it to start at all.

Do you just have a weak spark that's what it sounds like.

 

[NCSUcherokee]

A new optima and a new coil didnt change anything. Im going to clean the grounds and try a new cap/rotor tommorow.

 

[bajacalal]

It really does sound like an out of sync distributor or, the wrong sized rotor.

Did you try to reindex it by removing the whole thing, setting the engine to TDC and the distributor to the correct position? You mentioned you flipped it, but was it a couple teeth off in the first place? Also a fuel system problem. Did you test fuel pressure. How about the injectors, AND, nobody mentioned this, if the injector cables are in the right order.

 

[NCSUcherokee]

-Fuel pressure gauged out at 38 today
-The injector plugs are still labled from when i removed the engine, so i know those are right.
- I have indexed the distributor many times, moved it a few teeth forward and a few teeth back and reindexed it again so i don't think that is the problem
- Injectors are getting juice (unplugging them kills the engine)


Today i tryed swapping out the O2 and the TPS with ones i had laying around from the previous engine to no avail. The only thing to date to cause any marked change in the way the engine runs is the CPS. I tried cleaning the old one and threw it back it and it went back to running like crap but starting easy like it did before.

 

[carnuck]

Did you use the original flywheel? Someone on another list discovered the hard way that the 87 to 08/90 flywheel/flexplate and CPS are TOTALLY different signal than the later ones. It ran but kept causing running trouble.

 

[bajacalal]

Today i tryed swapping out the O2 and the TPS with ones i had laying around from the previous engine to no avail. The only thing to date to cause any marked change in the way the engine runs is the CPS. I tried cleaning the old one and threw it back it and it went back to running like crap but starting easy like it did before.

You seem to have narrowed down the possibilites quite a bit then. You mentioned the Cam and Crank PS sensors, may be time to take another look at that. The only other thing that I can think of, is that the timing chain was removed and the cam wasn't put in synch with the crank.

 

[NCSUcherokee]

Did you use the original flywheel? Someone on another list discovered the hard way that the 87 to 08/90 flywheel/flexplate and CPS are TOTALLY different signal than the later ones. It ran but kept causing running trouble.

I used the 89 flexplate, it went into a 90. would this cause a major problem? i had never read about them being different in that year range.


bajacal, i have swapped distributors also with no change, so i don't think it's the CamPS

 

[bajacalal]

Well, I guess youre sure the CPS is fine.

That date in question is the cut off point from the RENIX (renault) to the Chyrsler (HO) computer system which use electrically different but physically similar sensors (such as the cam and crank). If youres was built after that date then were talking about a Chrysler ECU, you say you have a 90 cherokee, so built late 89 to built 90 with RENIX ecu right? The 91 "year model" first produced around labor day '90 was the non-RENIX injection. What about the cam timing itself bieng off though?

 

[NCSUcherokee]

I dont think the timing chain jumped because i cracked open the valve cover to make damn sure the engine was at TDC last time i indexed the distributor. Both valves on #1 were closed when the timing mark was lined up.