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Jeep Cranks, Won't Really Start

758 Views 10 Replies 5 Participants Last post by  CP30
To start this off I was going on a trip and leaving the jeep behind, I was looking under the hood for some reason and left it open. It rained that night and it was shut the next day.

Apparently the light bar was on for quite awhile, I traced it to the relay getting waterlogged and shorting out, this fried the relay but the rest is good, the light bar is connected to the battery terminals, just including this in case it could've messed something up.

So! After I got back a few days later it started up fine, on the way to a friends house it stalled out, I stopped and it started right back up. Since it started back up I figured it was water in a connection and would evaporate out. Stupid I know. On the way back it got worse, the jeep kept stalling sometimes right after start, but mostly at idle speed or when I gave it more gas. It stayed running fine when I just kept it at a consistent speed. After one of the shut down start up cycles it threw a code for the camshaft position sensor being disconnected, but it went away on the next shut down start up.

The next day I tried starting it again, but it wouldn't turn over, it cranks fine though. I cleaned up the battery connections as well as blasted the fuse box, the camshaft position sensor connection, the oil pressure sensor connection, the three harness connections on the passenger firewall next to the engine, the three connections that plug into what I think is the PCM (the box on the driver side fender), and the coil rail connection.

I also tried replacing the camshaft position sensor, that didn't help. I believe I checked the crankshaft position sensor, but it's connection seems to be in a different place than I keep finding online. The sensor is at the 1 o'clock position looking from the front and the connection is at around 3 and behind it attached to a bracket on the transmission. I tested pins B and C on that connection and got a reading of around 60 M ohms, which I believe is higher than the proper testing range.

One more weird happening is after cranking it some times the oil pressure gauge jumps to above 80, but goes back to just above 0 after I turn the jeep off then on again.

Any help is appreciated and I can upload some photos if need be.
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Just got the battery checked, just in case there was some weird stuff there. It was bad, got a replacement, but that only made it crank faster.
First take off the air duct that connects to the throttle body and get a funnel and some straight gasoline and pour about a 1/4 to 1/2 a cup of gas into the throttle body and make sure you push the throttle valve/lever thing down to let the gas pass into the intake. Put the air duct back onto the throttle body then try to start it. If it starts that means you're not getting fuel. At that point get a fuel pressure gauge and check the fuel pressure and/or your hold pressure. If it still does not start after pouring gas into the throttle body then it is indeed a spark and/or electrical problem. I always eliminate the fuel question first and work from there.
Thanks for the reply! This was my second time typing up the original post, the power went out, but this time I forgot to mention that I have checked fuel pressure by pressing on the valve on the fuel rail. I will do a pressure test though just to make sure it's reaching the proper pressures.
I just went through a similar exercise after replacing and injector on my '99. The injector #3 wire was caught against the throttle cable support bracket. Engine was running great and then instantly stopped when I moved it. Kept cranking and would not start. I sprayed some starter spray into the throttle body and nothing. I checked all the injector and sensor connectors and tried cranking a few more times, still nothing. I had taken the fuel rail off to replace the injector so I pressed the valve and fuel sprayed out. Checked that a few times and definitely looked like I had fuel pressure. Next was spark. Removed a spark plug and then put the wire and plug by the block while I had someone crank the engine. No spark. I checked the CPS and saw infinite resistance between terminal b and c. After all that cranking, the check engine light finally came on. I forget the code, but the description was auto shut down circuit had no voltage. I did some googling and checked the ASD relay by swapping. Still no go. Did some more searching and found there is a 20 amp fuse in the engine fuse box. That fuse is triggered by ignition components including the injectors. I was looking for which fuse # it was and of course can't find it right now. It's a 20 amp fuse and was blown. I replaced that and it fired right up. My guess is when I moved the injector, it shorted against the bracket and blew the fuse.

Point of the story. check fuel and spark. It has to be one or the other missing.
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You need 3 things for an engine to run: Fuel, Spark or air.

Since air is the least likely, like the previous poster said, check fuel & spark.

You can have pressure on the rail (from build up from the cranking) but have not enough pressure to run. Change out you fuel filter, its $15 and should be done annually anyways. Test your injectors (you can do this with handtools, youtube has vidoes).

Test your sparkplugs (this can be done with a sparkplug tester or manually).

Also check all your fuses & relays, and make sure that you validate your gas hasn't gone bad (or you pumped bad gas into your tank -- this has happened to me).

Check your oil pressure as well (there's gauge for that), chances are its a bad sending unit (only used to show on dash), but you'll want to be extra sure.
I would not pour any gas into the intake.

If necessary, a 1/2 second burst of starting fluid will tell you if the engine will run. Checking/testing fuses and relays is basic troubleshooting and where you should begin problem solving.

Letting the battery run down will delete the idle settings from the PCM, and there will be difficulty starting. You need to depress the gas pedal about halfway while cranking and them keep you foot on it until the idle steadies. If nursing the gas pedal does not help it start, you will need to follow up on the Cam Sensor code, and properly test the Crank Sensor.

1997-2001 have an in tank fuel filter that is not changed unless fully clogged and there is low fuel pressure.
I would not pour any gas into the intake.
I second this.

1997-2001 have an in tank fuel filter that is not changed unless fully clooged and there is low fuel pressure.
Note to self, don't get a 97-2001 model.

I'd still pull the filter and swap it anyways. Its a ***** to do, but if you've been cranking it constantly it can slowly build up enough pressure that the rail will test good, but it won't be enough to completely start the car or keep it running for long, once it burns it out of the rail. That was *exactly* what was happening to mine (it started but only after I manually primed it 5-6 times), and now, my 96 starts up first crank every time. I also ran premium gas in here and dropped 8oz of Marvel's Mystery Oil to clear out any other gunk.
What's the difference between "starter fluid" and gasoline? They're both introduced into the intake through the throttle body and they both burn and they both do the same thing. Determine if you got a spark/electrical issue or a fuel delivery issue. Be safe and use a funnel and you're fine.
Be safe, smart Cherokee owners DO NOT pour gasoline into the fuel injection intake. If there is a backfire, flaming gasoline could fly out of the intake and set the engine bay on fire. One shot of starter fluid, 1/2 second in duration, is all that would be necessary to confirm ignition and running, and any starter fluid backfires would not set flame to the Cherokee.

If a simple to perfrom fuel pressure test shows 49 psi +/- 5 psi of fuel pressure when the engine is running, the in-tank fuel filter does not need changing for any reason.
I can't see flaming gasoline flying out of the intake and into the engine bay. There's not an open channel from the intake into the engine bay. It's a closed circuit by the throttle body and the air duct connected to it. There's no where for it to go except back through the throttle body. And I said to put the air intake duct back onto the throttle body before trying to start it. It's safe enough all right. All long as you don't spill gas outside the throttle body onto the engine. Hence the funnel I reccomended. Use starter fluid or gas. Makes no difference. They're both the same thing. One sprays in one pours in. I prefer pouring a little gas in because the amount of starter fluid you spray in might give you a false result. If that thing CAN crank over and start it deffinitely will with a 1/4-1/2 cup of gasoline whereas it might not with starter fluid sprayed in. I deffinitely know exactly what the situation is with fuel delivery or spark with 1/4-1/2 cup of gas.
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