How to fix back fire in my carb 1985 jeep cherokee

Firing order doesn't change on its own and then cause misfires. Did you change something? Most likely cause is spark plugs.

https://www.google.com/search?q=1987+Jeep+Cherokee+2.5l+2x4.+Firing+order

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http://www.autozone.com/repairguides/Jeep-Wagoneer-Commando-Cherokee-1984-1998/FIRING-ORDERS/FIRING-ORDERS/_/P-0900c152800a988f

no need to adjust the timing you need to turn the rotor to the left a it will start and it's not a v6 jeep only make inline6

The firing order for the Jeep 2.8l engine is:1-2-3-4-5-6
and the locations are:
on the drivers side front to rear 2-4-6
passenger side front to rear is 1-3-5
If you look straight back from the water pump to the distributor splitting the capcylinder #1 is the first one to the left.

Could be a bad ignition module or could point to faulty wiring. The longer your vehicle runs the hotter some electrical components get and that's the 5 - 15 minutes it wants to cool down.

so you tryed to check the timing how about the destibiter cap an the ponts !

1985 Jeep Cherokee came with either a 4 cylinder 2.5L with a 1 barrel carb or a 6 cylinder 2.8L with a 2 barrel carb. The 4WD only had the option of a 4 cylinder 2.1L turbo Diesel.

Engine size would be a start.

check your firing order as well as your timing