99 Cherokee Sport, 4.0L, 6cyl, auto

My son drove the Cherokee last Thursday night. Come Friday morning, it wouldn't start. It cranks good, I tested the battery (tested good), fuel pressure is 45, spark verified.

So....timing?
Computer not opening injectors? (I'm sure all 6 injectors wouldn't go bad all at once)

Any help will be fantastic.

Thanks,
Grizz

 

Did you actually see the spark by pulling a plug, grounding, it cranking the engine and watching? You are looking for a strong, blue, snapping spark. Yellow/orange/white indicates a weak spark which can absolutely not be strong enough to start the engine.

Okay, if you have blue spark, then try this quick and dirty test. Spray a small amount of starting fluid into the intake or a splash of gas. If the engine starts and runs momentarily, you have now verified a FUEL DELIVERY problem.

Testing to see if the injectors are firing with a "noid light" is another technique.

Timing and injector pulse are controlled by the computer.

 

My post states "spark verified". Yes, the spark tester lights up. Also, spark was seen on pulled spark plug.

Fuel rail has pressure of 45 at 'rest', 45-50 while trying to start.

More than one can of starter fluid was used in the first day of troubleshooting, into the throttle body.

 

Did it work with the starting fluid?

 

Get a noid light and see if you have injector pulse. If you don't have injector pulse my money would be on a bad Cam Positioning Sensor.

 

Starting fluid has had no affect. Been trying that off and on throughout the issue from start to finish.

I think if I have spark, then it isn't the CPS.

 

And you are getting a spark at all plugs?

 

x2

 

x3 cam sensor

 

Iv'e had the same problem on mine lately and the answer to most of the discussions was the CPS. Fortunately for me my car randomly fired back up. But I do plan on replacing the CPS when I get the dough. Good luck though.

 

If starting fluid doesn't work, you are 100% sure you have GOOD spark, and youv'e got pressure at the fuel rail, its gotta be something keeping injector pulse from hitting.

Also, you do not have fuel like you said earlier. Just cuz you have pressure at the rail doesn't mean your getting fuel.

 

Ya i would get a noid light to check injector pulse. Real quick test and you can probably even borrow one from the ol autozone.

 

i have had the same problem before, try to unplug the MAP sensor, plug it back in and try to start it, i did it and it starts right up, ended up spraying some contact cleaner in the connector and hasn't happened sense!

 

+1 noid lights


you can get them (rent) at AutoZone

 

http://www.2carpros.com/articles/how...-fuel-injector