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junkyard zombie
06-06-2015, 04:24 PM
My son and I replaced the fuel pump on his 97 XJ this morning. When we tested the pump and got her running, she threw the serpentine belt off. This is about the 3rd time the belt has come off. Everything looks lined up but this could be a catastrophic failure if we were out on the road. We are still trying to get her road worthy and it is not street legal yet. Is there any history of this issue on these vehicles or is there a mod that we need to be aware of. Thanks in advance for any knowledge you may share.
4.3LXJ
06-06-2015, 04:59 PM
No history Cecil. Check all pulleys to see that they are free. It might just need a new belt
junkyard zombie
06-06-2015, 05:04 PM
Thanks for the reply. We changed the belt when we first got this rig about 6 months ago. I will go back and check all the alignments and make sure it is tight. Thanks again.
Mudderoy
06-06-2015, 05:45 PM
My son and I replaced the fuel pump on his 97 XJ this morning. When we tested the pump and got her running, she threw the serpentine belt off. This is about the 3rd time the belt has come off. Everything looks lined up but this could be a catastrophic failure if we were out on the road. We are still trying to get her road worthy and it is not street legal yet. Is there any history of this issue on these vehicles or is there a mod that we need to be aware of. Thanks in advance for any knowledge you may share.

Check to see if the pulley on the harmonic balancer is moving forward, it should be even with the rest of the balancer.

I had mine come apart on the 98 and the 99 started doing the same thing so I replaced it.
Carves
06-06-2015, 06:45 PM
X 2 on the harmonic balancer as a suspect.

It,
... or one of the idler pulleys having collapsed bearings, which is normally pretty obvious with the belt off tho ...and they usually squeal like a banshee when they are buggered.
Pookapotamus
06-06-2015, 06:54 PM
How tight did you have the belt?
junkyard zombie
06-06-2015, 08:02 PM
We had it pretty dang tight....We found a bad idler pulley on it when we first bought it and initially got it running. But due to work constraints we have put it on the side burner since about the middle of March. But I don't remember it being over tight or loose. Then when the fuel pump died, it sat for another couple weeks