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Help with no start after swapping engines

C

cmexlr8

NAXJA Forum User
Location
Chatsworth, Ga
I have a 2000 with a 4.0. I bought the jeep with a dead motor(seriously overheated - milky oil). I bought a used motor from a 2002 and swapped on my intake and accessories and sensors. I have everything hooked up and I am trying to get it running and it will turn over and it pops back through the throttle body. The cranking seems irregular too almost as if it was firing way advanced.
 
Crankshaft Position Sensor (on the bellhousing) is the first one that pops into my mind. They can be easily damaged when swapping engines, and they will often look fine.

I'm not sure what replaced the old Cam Position Sensor when they went to the distributorless ignition; but when my Cam sensor went on my 1994, it did pretty much the same thing as yours.

:)
 
For 2000, you need a good CKP crank position sensor and CPS cam position sensor (which is the distributor-like mechanism). The CPS must be timed like a distributor using the toothpick method. I'll search for the write-up.
 
I indexed the cam position sensor this morning and it is still not cranking. It still acts like it is out of time. It sounds and acts like it is too advanced( popping back through the intake, kicking back on the starter )

I also checked for resistance on the pig tail for the crank position sensor and didn't get any resistance, though it was very difficult to get the leads on the b and c pins.
 
Please correct me if I'm wrong, but it IS cranking. It is NOT firing. You still are using the coil rail from the 2000, correct? Was the 2002 motor from an XJ? I feel stupid asking, but I though the last year was 2001.
 
Mine is a grand cherokee. The motor came from a later 02/03 grand cherokee. I am using the coil rail that came on the motor I bought(i.e, the later model one). They look exactly the same.

I just went out to the shop and pulled the valve cover to make absolutely sure I was on the compression stroke for TDC on number one. I then pulled the cap off of the cam position sensor and the holes are lined up. I even went so far as to take the sensor from the original motor and tried it - still the same issue.

The engine turns over, but it does not run.

Can the flexplate only go on one way? It seems like when I put it on, the holes only lined up one way.
 
So your vehicle is a 2000 grand, you put the motor from a 02/03 grand into it, and put the 2000 flexplate on it? You could try swapping the CPS (cam position sensor) assembly from the original.
 
Yes, yes and yes.

I did swap the cam position sensor from my old block - still no change. I just bought a crank position sensor from Oreilly's, so I am going to try that. It was only $33 bucks - I have been reading where it is close to $100?
 
Okay, now that I have messed with it long enough, it is definately trying to start, but it acts like it has too much timing. I am starting to question the timing chain being a tooth off or maybe the balancer is spun a little.
 
at this point, the plugs may be fouled with fuel. take the plugs out and burn off any excess gas. then reinstall. you need to confirm that the flexplate(cks) and cam timing(cps) are correct.

did you see the new motor(2002) run before you bought it?
 
No, I did not see it run, I checked compression and checked the oil and looked under the cap.

I actually got it to fire a little better by taking the cam sensor and oil pump drive out and bumping it back a tooth which allowed me to retard the sensor more.
 
WOOOHOOO - it runs! Sometimes it can be something so simple. I pulled all the plugs and checked them and they were sooty, but not fouled, so I put them back in. I had intended to swap back to my cherokee's original coil pack and when I went to go get it, I noticed it was a little different. The plug at the back of the rail where it plugs into the vehicle harness, pointed straight down on the original one, but the one I was using from the motor I bought pointed off to an angle. I did not notice it when I was doing the swapping. Anyway, long story short, coil packs are apparently not interchangeable between 2000 and either 2002 or 2003(I am not really sure which year the motor I bought is from).

Thank you guys for all your suggestions. The only part I bought that I ended up not needing was the crank sensor, but at least I have a spare now.
 
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