Hello all! My 1990 XJ 4.0 cranks for 10 to 20 seconds before it fires irregardless if its hot or cold. Somewhat better when re-starting within a few minutes like say stopping for gas etc. be. Any ideas? Engine runs great other wise after 176K. My first Jeep, by the way, so lots to learn!

 

Try the poor mans prime on it. When first starting her up turn the key on to the point that you hear the fuel pump coming on but do not start it do that 2 or 3 time then try to start it. If that work that will mean that you your anti-drain back check valve is stuck open. It won't hurt anything leaving it like that but you will have to prime the fuel line to get her going.

 

Hello Robert! Thanks for the tip. Just where is this check valve? The starter has been replaced at some point. Not surprised, the last one probably cranked itself to death. it's time to find and fix the problem! Any advice?

 

Well, the above advice regarding is something!
Refreshing your connections on the starter but also on all ground connections is never a bad thing and gives you a good reference for future issues.
The poor man's prime is a good thing to see if drain-back valve of pump itself are issues, but keep in mind XJ's tend to have a somewhat longer cranktime anyway.
See if robert's advice improves your cranktimes (I've been doing it for months now and let us know. If not, we go from there.