I've just finished rebuilding my 2000 Cherokee's engine. It's the 4.0 and has a camshaft position sensor and coil pack setup. I made sure I aligned the timing gears properly when I put the new ones and timing chain on. We have compression, fuel, spark, it just won't start up. It just cranks repeatedly. I replaced both the camshaft position sensor and crankshaft position sensor. I put the first cylinder at tdc of the compression stroke and then put the cmps in properly with the oil pump insert at 11 o'clock and bolted it all down and still no start up.

At this point I'm clueless and open to any ideas. I'm going to check for trouble codes this afternoon when I can work on it. Any ideas why it won't start?

 

Get a "Noid Light" set and make sure the injectors are firing. Is the fuel pump turning on and pressurizing?

 

I checked the coil pack for spark and only a few cylinders were firing. The coil pack is new so I guess the timing is off? Or the pcm is bad? I tried to check it with the scan tool and it would lose connection over and over.

The fuel pump is working and we do have fuel pressure.

 

The only codes we currently have on the Cherokee is a neutral safety switch failure. Would that not allow the Cherokee to turn over? Just crank?

 

Turn over = crank (they mean the same thing).

The engine can basically do two things when the starter is powered. It can crank (spin) and it can start (ignition occurs and the motor begins to run). A failure to start can usually be described by the following two terms:

No Crank Condition
Cranking No Start Condition

If the NSS is working properly and does not detect that it is in the P or N position, it will not even allow the starter to spin (resulting in a "no crank condition").

 

I'm not much help with a 2000. I've read indexing the dizy can be tricky. EDIT, WHOOPS! (NO DIZZY!) One tooth off is trouble. Also wanted to mention if there is compression, fuel and spark and it won't fire, being flooded might be the problem. Yours might be like mine in that if you hold the petal floorboarded, it shuts off fuel completely with max air, to help "clear" a flooded engine.

 

.You use tooth pick method for sensor install ?

 

WHOOPS! MY Mistake above...no dizzy. Here is something though. I have two 90"s. One came to me with the ring slipped and the timing mark off. Did you use the original harmonic balancer? Could a guy check the woodruff key slot on the crank, to the TDC mark on the damper pulley? The rubber under the outer ring of the crank pulley is known to fail.

Btw, "back in the day" a guy might pluck a piece of straw, set it in #1 plug hole, then watch it while rotating the engine to get an idea of TDC. Plastic works. Easier than connecting a compression gauge line to clear vinyl tube, filling the works with oil and finding TDC with the peak level. Also, with the valve cover off the rockers get even at the top of the exhaust stroke. A straightedge across the rockers on #6 might be level when #1 is at TDC.

 

I rechecked everything and it is all properly aligned. I am making sure it's the compression stroke by waiting till I feel pressure push my finger out of the first piston while turning the crankshaft and then I use the timing mark on the harmonic balancer (which is new) and then align it with the "0" on the timing chain cover marks. I used a Allen wrench to keep the cmps in proper alignment and threw it all back together and it just cranks. No starting.

I did fix the NSS today and the jeep will start but misfire a bunch and die. No change even after I tried to set fuel synchronization again. No check engine codes except intermittent loss of the cmps or ckps.

 

I'm mostly bumping your thread, largely clueless. I try bonehead things (hence "Flintstone") sometimes. Knowing nothing I might see if it runs with shots of starting fluid. (indicating a lack of fuel). I do carry a spare CPS...If you were to replace yours with no change you would likely have a spare also.

Hopefully someone more "in the know" for a 2000 will chime in. I'd mostly trust the new crank pulley, but the CPS and cam sensor....you may well have gotten a bad something. One story goes they mostly come off the same line. Dealer gets those that test best, down to auto zoned ect, who gets worst. I go to Napa with Car Quest in there. About no chance I would buy a sensor from Artzone or O'Whrearewe's

 

HELP!

You didn't mention what state you are in. Unless you are in CA or Hawaii, you should be able to take it to a "big box" parts store and have them try a scan. (I get it, a bit tough if it won't run). Seems maybe your problem might be around there. If two different scanners can't get a reading... Idk. Was it running before the rebuild?

 

It was running prior to the rebuild. I rebuilt it cause the previous owner said the block was cracked and when I tore down the engine the head and head gasket weren't put on right and a piston had melted to the sidewall. I did the machining myself with the help of a engine machinist and put it back together and replaced the cmps and ckps to get it to start once to get it home and then it wouldn't start again.

 

So far I've replaced the coil pack, almost every sensor, and the harmonic balancer and timing chain and gears are new. A friend told me the next thing to do if that's all checked out and fine is to take the pcm out and look for any shorts or burned areas from excessive heat.

 

Is cam sensor turning when engines cranked over ?

 

I'll have to hop under and see if the crank sensor is moving any. I won't be able to check that for a few days with finals for classes coming up and work. I'll let you know what I find.