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Distributor Install

rws

NAXJA Forum User
Installed a new distributor into my 1990 4.0. I had to cut the "ears" off the distributor in order to set the timing and as a result the vehicle runs perfect. My question is why did this rebuilt distributor not just drop in as per instructions in the FSM??
 
You've got a distributor that works, but isn't the right one.

I've replaced distributors on my 94 4.0l XJ and on a friends 92 4.0l YJ. Both of them dropped in with no modifications. And in reality, you don't "set the timing" with the distributor on an HO 4.0l, that's all done by the ECM. The distributor is fixed in place.

Oops.... just noticed that it's a 1990 Renix. Still, you shouldn't have had to make any mods so that it would fit.
 
Sounds like the wrong distributor. I just replaced mine a couple of months ago, and it just drop right in and runs great. You can't set the timing with the distributor, atleast thats what i've been told.

'90 4.0L
 
Puchased the distributor from NAPA and I checked the number engraved into the side of the distributer ,it was the same so it was the correct distributor. I actually put the old one back in several times and it lined up properly each time but the new one was either one tooth forward or backward. To install the new one in the correct position I had to cut the ears off. After installing the new one I checked the intial timing with a timing light and it was at about 14 degrees which is what I would would expect it to be.
 
I wouldn't care if the numbers ARE the same, if you bought a replacement distributor, you should not have to modify it to make it fit.

You probably would have to reach down with a long handled screw driver and turn the oil pump a bit, but the new assembly should go in exactly like the old one came out.
 
I did turn the oil pump to the correct position prior to installation. However I think I have the answer and will repeat it her for anyones future reference. After doing an internet search I came across a distributor indexing procedure for 1988 4.0 jeeps using the renix system. The TSB bullitin is #18-53-88 and apparently if you replace the cam sensor which is part of the distributor the distributor may have to be indexed before the engine will run properly. This involves cutting the ears the ears off the distributor to achieve proper alignment of the rotor. Mystry solved.
 
If you cut the ears off,what keeps it from turning and re-setting the timing.
Wayne
 
The problem isn't the distributor, the problem is in the drive gear. Jeep had a problem with some of the Renix engines not running right, and it was traced to a problem with either the distributor gear or the distributor drive gear on the camshaft being a few degrees out of spec. The correction was to grind off the distributor locating tabs and manually position the distributor so that with cylinder number 1 at TDC on the compression stroke, the rotor was just past (beyond) the contact in the cap with an air gap of 0.020". There is (or was) a TSB describing this.

A rebuilt distributor will have a new drive gear, but probably not a drive gear sourced from DaimlerChrysler, so it's not unlikely that it may be a few degrees out of spec.
 
Eagle, you are correct, the rebuilt distributor had a new drive gear. Its intresting how a 20 minute job can wind up taking the whole afternoon.
 
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