Won't start
Thread Starter
Junior Member
Joined: May 2015
Posts: 47
Likes: 0
Won't start
Hey guys I was fixing the front brakes on my 97 cherokee then took it for a test drive came home and parked it. The next morning I went out and it won't start it cranks but won't fire so I just check fuel pressure it goes up to 50 then when I Crank it over it stays between 40 and 50, any other thoughts?
CF Veteran
Joined: Nov 2010
Posts: 5,840
Likes: 117
From: In the middle of Minnesota!
Year: 1999
Model: Cherokee
Engine: 4.0
As mentioned, gotta verify spark. Pull a plug, keep it attached to the plug wire, place the plug electrode near a good engine ground. Have a buddy crank the engine over while you observe spark quality. You are looking for a strong, snapping BLUE spark. Yellow/orange/white indicates a weak spark which may not be strong enough to start the engine. Weak spark is usually caused by a failing ignition coil.
If you have good spark and you've already verified fuel pressure which looks to be reasonable, next I would install a noid light to see if you are getting the proper injector "pulse" from the computer.
The above two tests are going to narrow down what you look at next. It's a process of elimination. Good luck and keep us updated!
If you have good spark and you've already verified fuel pressure which looks to be reasonable, next I would install a noid light to see if you are getting the proper injector "pulse" from the computer.
The above two tests are going to narrow down what you look at next. It's a process of elimination. Good luck and keep us updated!
Last edited by tjwalker; Dec 29, 2016 at 11:49 AM.
CF Veteran
Joined: Jan 2012
Posts: 2,208
Likes: 5
From: Ocean County, NJ
Year: 1998
Model: Cherokee
Engine: 4.0L
As mentioned, gotta verify spark. Pull a plug, keep it attached to the plug wire, place the plug electrode near a good engine ground. Have a buddy crank the engine over while you observe spark quality. You are looking for a strong, snapping BLUE spark. Yellow/orange/white indicates a weak spark which may not be strong enough to start the engine. Weak spark is usually caused by a failing ignition coil.
If you have good spark and you've already verified fuel pressure which looks to be reasonable, next I would install a noid light to see if you are getting the proper injector "pulse" from the computer.
The above two tests are going to narrow down what you look at next. It's a process of elimination. Good luck and keep us updated!
If you have good spark and you've already verified fuel pressure which looks to be reasonable, next I would install a noid light to see if you are getting the proper injector "pulse" from the computer.
The above two tests are going to narrow down what you look at next. It's a process of elimination. Good luck and keep us updated!
Thread Starter
Junior Member
Joined: May 2015
Posts: 47
Likes: 0
Thank you
Ok I have been busy not much time to work on the jeep, but I put gas in the throttle body and still no fire, does this eliminate the injector pulse problem? And I will be checking for spark in the near future
