Tuesday, August 19, 2008

Changing the rear pinion seal

Last night we replaced the rear pinion seal on Jenny's XJ. Her Jeep has the Chrysler 8.25 rear end. The gear lash of the differential is set partly by the amount of crush on the spacer under the pinion bearing, so changing the seal has the potential to up set the alignment of the gears.

After removing the drive shaft, we carefully marked the nut and the pinion shaft. Then while holding the yoke with a pipe wrench and turning the nut with a socket, we carefully counted the turns required to remove the nut. In our case it was nine turns exactly.

The yoke came off easily with the nut removed. I used a chisel under the metal lip of the old seal to drive it out. After cleaning up all the surfaces, and inspecting the yoke for wear, we installed the new seal.

I used a hammer and a seal driver to press the seal in flat against the differential housing.

We then installed the yoke being careful not to damage the new seal.

We then reinstalled the nut and carefully counted the turns to put it back into the right spot. A little dab of lock tite was put on the threads as a precaution.

After tightening the nut back to precisely the same spot as it came off, I turned it just a little bit more to ensure it was tight.

We then reinstalled the drive shaft and filled the diff with fluid to replace what had leaked out.

A quick test drive shaowed it was all sealed up. No more stinky burning diff lube on the exhaust!

Monday, August 11, 2008

Jeep XJ Fuel Pump Relay

I have been dealing with a couple of Jeep XJ Cherokees lately that have had intermittent fuel delivery problems. The first one was Jenny's 92 XJ. Occasionally on hot days her jeep would appear to vapor lock. While vapor lock was common on systems where the fuel pump was at the engine and pulled fuel from the tank, the pressurized system of the Jeep should be immune to vapor lock. Jenny's Jeep would also occasionally read low fuel pressure ont he fuel rail and then at other times read the correct fuel pressure. Bypassing the ballast resister would sometimes cure the low fule pressure problem.

Next my son's 91 XJ began havign trouble starting. It would sometimes fire then stumble an ddie only to start right back up. At others times it would simply spin but not fire at all. Testing the fuel pressure at the rail would show fuel and checking spark gave me quite a jolt. But it simply would not start. Sometimes it would seem to start while holding the key in start but as soon as the key was released to run his Jeep would die.

The most annoying part was that after he would call me or my dad to come rescue him, we would get there to check it out and it would fire right up. Pull it in the shop to test it and it would start and run fine every time.

Finally, one day it failed to start while I was there and i had a chance to keep experimenting with it. After quite a bit of head scratching, I found that the fuel pump relay was not always making contact. I swapped his cooling fan relay in to the slot to get him home while I stopped by the parts store to get him a new relay. I picked up one for Jenny's Jeep while I was there.

Tuesday, August 05, 2008

Working with the boys

This weekend I took my younger son will to see his brother Scott. Actually Will took me along only because he needed a navigator.

We spent some time first replacing the master cylinder in Scott's XJ Wagoneer. He thought it was pretty scary to drive when the pedal went to the floor with no braking effort.

Swapping the master cylinder was an easy task once we got the right unit from O Reilly's. Getting parts for an XJ Wagoneer is always a challenge. When we went back to swap out the unit that was apparently for an SJ Wagoneer we simply asked for one to fit a Cherokee. That one matched up. Since he did not have a vice at his rented house, we went ahead an mounted it on the brake booster and did the bench bleed procedure there. After attaching the lines and quickly bleeding all four corners he has a nice firm brake pedal again.

Next we moved to Will's XJ. His dome lamp fuse was blowing ever since he changed his headliner. Assuming that there was a bad wire somewhere, we had removed the headliner an checked everything last weekend. We found nothing so we put it all back together.

The memory for the radio and clock are also fed from the dome light circuit so we made a plan to bypass the short and just power up the radio from another source. When we checked for a short at the radio every thing tested fine. We were able to power up the radio and clock with a jumper and ensure it all worked. So we looked further to find the short from this side. Everything we tried tested fine. So we went back to the fuse box and tested again. No more short. So we tentatively put it all back to getter and put in a fuse to see what would happen. Happily the fuse stayed an the radio, clock and dome light all work properly now. The clock did show 15:14 when it started up but it reset correctly when Scott pushed the buttons to set the time.

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