I just got a 92 Cherokee and it seems to have a bit of a problem starting. It starts everytime but you have to hold the ignition for about 15-20 seconds for it to start. Would anyone know what might be causing this?

 

Bad check valve in the fuel pump possibly. Try this:

Turn the key to On,but don't go to Start. Do this 2 or 3 times, and then go to Start. Anything change?

 

Mine does the exact same thing. Gets worse in the winter though. My problem is definitely the fuel pump. Before that, check your starter and your battery, swap relays out, and check for any shortages.

 

Sounds like check valve. Very common problem with these cars. There's a one-way valve in the pump that is supposed to keep fuel from draining back out, but it eventually wears out, and when that happens you only have pressure when the pump is running but the fuel drains out rapidly when you turn the car off.

Only way to diagnose for sure is rent/buy a fuel pressure tester and hook it to the Schraeder valve on the fuel rail. If pressure falls off rapidly when engine is killed, the check valve is shot. With pre-96 XJs you can add an external check-valve in the supply line to keep it pressurized, but the real long-term fix is a replacement fuel pump.