93 Cherokee 4.0 starts but won't run on own

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09-30-2020, 10:36 PM

#16

doublechaz

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Year: 1988

Model: Cherokee (XJ)

Engine: 4.0

I"d pull them out and set them in carb clean over night. They can't really get any worse. Plus you can inspect all the o-rings while you are at it.

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09-30-2020, 11:44 PM

#17

lawsoncl

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Year: 1989

Model: Comanche (MJ)

Engine: 4.0

Quote:

Originally Posted by doublechaz

I"d pull them out and set them in carb clean over night. They can't really get any worse. Plus you can inspect all the o-rings while you are at it.

Do you have good fuel pressure while cranking? You might have pressure, but if the fuel filter is plugged or the pump is really marginal, then that pressure is going to disappear as soon as you crank. If you're going to go to the effort to pull the injectors, you might consider just replacing them with a set of refurbished 4-hole Bosch injectors. jhc7399 on this forum sells them for a good price.

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10-01-2020, 12:02 AM

#18

doublechaz

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Year: 1988

Model: Cherokee (XJ)

Engine: 4.0

Quote:

Originally Posted by jeep_newby

Picked up a 93 Jeep Cherokee (4.0 6-cyl) in great condition. However, it sat in a garage the last 7 years so I drained the fuel. Then I tested fuel pressure at the fuel rail. Came in at 35 PSI when in "on" position, ~40 PSI while turning over.

I emptied the fuel tank, flushed the fuel lines, and added ~ 1 gallon of new fuel. Then, to rule out bad fuel in the line I used the last fuel flushed throught the fuel rail to start the car by pouring a little into the intake. It started the car just fine but it still won't run on it's own.

Can't figure out what to check next....

Thinking maybe camshaft position sensor (can't figure out where the heck it is) or crankshaft position sensor (want to rule out former before changing that). Or maybe whatever tells the injectors to open?

I have a multimeter and basic tools.

Any ideas what steps I should take next?

First post and some of the other posts specify 35 PSI at the rail and 40 PSI at the rail while cranking.

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10-01-2020, 11:25 PM

#19

jeep_newby

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Model: Cherokee (XJ)

Problem found, thanks to all of you!

The injectors were stuck (closed). All of them! To fix, I removed them, did the 9V battery test to hear or feel if they clicked. That didn’t work so I gently poked the port where fuel comes out with a needle thinking it might break them free. Felt them “give” a little. Then did the 9V battery test again. And I heard a sweet “CLICK”... Then I soaked the last inch or so for a bit in carb cleaner for ~30 mins to hopefully clear out some of the gunk.

Put it back together and the Cherokee fired right up!

Thanks everyone for the help!

Can’t wait to get it on the road after a few more regular maintenance items.

Thanks again!