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RoldOvr05 01-20-2012 07:46 PM

Rebuilt motor, no start - million options!
I picked up a 2000 TJ with a bad motor. I bought a junkyard motor, tore it down. Machine the head and block. Complete rebuild except kept stock pistons, crank and cam. Clearances within spec. Install motor, hook up all the wires. Problem is when I go to start it just cranks.

Here is what I know:
1) I am getting fuel. Don't have gauge but smell gas, hear fuel pump kicking on and when valve on fuel rail pressed, gas comes out.

2) Figured I could have been rough on crank sensor since didn't remove when motor taken out. I replaced with new crank position sensor. It had the air gap piece that falls off when started.

3) Had an extra distributor and coil laying around. I used different combinations to see if one of them was bad. Distributor gear looks fine.

4) New battery

5) Starter is engaging and turning the motor.

6) Went through wires again. Cant find anything unplugged.

7) Timing - Timing marks were lined up. Both gears can only go on one way. Played with the location of the distributor.

Any help would be greatly appreciated!

Not my first motor rebuild.

jeepwayoflife 01-20-2012 07:49 PM

Do you have any spark plugs in it? :p sorry I can't really help but im sure someone will step in :)

hammmike 01-20-2012 07:55 PM

Do you have fire at the plugs? Take a compression check on one cylinder and that will tell you if the cam is in time. (Good compression)

cuder 01-20-2012 08:00 PM

You didn't say anything about the plugs firing. Is it at TDC on the #1 cylinder on the compression stoke? How many motors have you rebuilt?

RoldOvr05 01-20-2012 08:22 PM

Built about 6 or 7 complete motors. Not sure of spark. Has the coil pack so can't just watch for a spark. How can I check spark on these?

RoldOvr05 01-20-2012 08:38 PM

Went out to get compression results. Damn tester threads aren't long enough to thread into head. Luckily tried on spare head in basement before went outside in the cold.

Rusty jeep 01-20-2012 08:39 PM

Sounds like the dist is not clocked properly. I did the same thing about 3 months ago.

cuder 01-20-2012 08:47 PM


Originally Posted by RoldOvr05 (Post 1943070)
Built about 6 or 7 complete motors. Not sure of spark. Has the coil pack so can't just watch for a spark. How can I check spark on these?

With the coil pack off, put a plug in and then ground the plug at a ground point.

DMH2021 01-20-2012 09:03 PM

Make sure the distributor is clocked the correct way. I replaced a manifold on a different motor and installed it with the rotor cap at 12 o'clock when it should have been at 6. If you're getting fuel and some spark you should be getting something. Pull a plug, keep it connected to the wire and see if you are getting a spark to the cylinder. Also, see that the plugs are wet with fuel. Guy built a motor and duct taped the head ports to keep them free of junk. He forgot to remove the tape and put manifold on. Fuel was getting sent but not to cylinder. He figured it out after finding dry plugs.

DMH2021 01-20-2012 09:05 PM

....also, if it's just the distributor clock wrong the motor will backfire and some feed back, not just crank like you said.

RoldOvr05 01-20-2012 09:09 PM

Wasn't sure if disconnecting entire coil pack would still be ok but makes sense. Tested 3 plugs and each had a weak spark. It was night and still had to look for spark. Thought about distributor. Installed the same way as it came out. Length of wire isn't enough to allow it 180 degrees out. It certainly can be a few degrees off. I played with placement when trying to start

cuder 01-20-2012 09:29 PM

Bring the #1 cylinder to TDC on the compression stroke. Then make sure the timing mark on the harmonic balancer is at 0 deg. Now look at the rotor and make sure it is pointing at or before the post that the #1 wire is plugged into.
If you just installed the distributor the same way it came out of the other motor then the plug wires are probably off from where they need to be on this motor.

jkaufman_95 01-20-2012 09:31 PM

Side question, what are the other specs on the jeep? (color, top, package, fenders) jw :D

DMH2021 01-20-2012 09:36 PM

I'm guessing that since you rebuilt the motor you replaced the spark plug wires and plugs. If you didn't that might be the cause of the weak spark. If so, then it could be a bad coil.

RoldOvr05 01-20-2012 09:59 PM

Although it snowing, wanted to try flipping the distributor guts 180 degrees out. Same thing although it did give a puff thru the throttle body. When rebuilt, new plugs but reused coil since was running. On the little distributor, what is the pointer of the rotor. Once the cap is removed the spot where a rotor would usually be is just a half circle.

RoldOvr05 01-20-2012 10:02 PM

Jeep was a good find - once running of course. $500 - grey, soft top, automatic, 120,000 miles, 4 " lift, brand new 33 x 12.5 BFGs

jkaufman_95 01-20-2012 10:04 PM

Ah used to own an automatic 2000 that's why I ask, but that's not it lol

cuder 01-20-2012 10:42 PM

Ok, I looked at this PDF and see that there is a alignment hole to use a temporarily pin to lock the rotor to cylinder #1. Look on page #17, fig. 32. Hope this helps.

RoldOvr05 01-21-2012 12:30 AM

Ok, so couldn't figure out why people kept talking about damn plug wires and rotors. Come to find out I failed to mention i have a 4.0l. The last post was awesome. Its 1:30am and I just came in from the 2 inches of snow cause I had to try. Followed directions and motor started up. Took 8 seconds of starting - I know its too long. Ran rough. Tried to restart and same thing. Granted its late and snowing. I will go back out when the weather is better, and the sun is up, and retrace my steps to make sure its correct. Will keep everyone posted.

RoldOvr05 01-22-2012 04:41 PM

Redid the timing steps and she started right up! Thanks for the info.

freeskier 01-22-2012 05:04 PM

10 Attachment(s)

Originally Posted by DMH2021 (Post 1943277)
....also, if it's just the distributor clock wrong the motor will backfire and some feed back, not just crank like you said.

I know the OP figure it out, but I'm pretty sure if the crank position sensor and cam shaft position sensor (which is in the distributor) are not in sync the computer will trigger the ASD, which will allow the engine crank all day long but won't have fuel or spark.

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