Jeep sat for 4 months an wont start

Posted the below text in the regional section and I was recommended to post it here to get some more eyes on it.

"Hello gents,

I had to be away from the Jeep for 4 months and now it wont start. I charged the battery (which was dead when I got back to the Jeep) and I tried jumping it. It will now crank, which it wouldn't do before but it won't turn over. The charger is also showing about 12.3 volts (on an Optima yellow top that was replaced 2 months before I left).

It has gas in the tank and the schrader valve on the fuel rail shows there is fuel getting to the rail but I did not have a way to test the pressure.

The cap, rotor and wires were replaced about 2 months before I left as well and everything worked fine before I left. I popped the cap off and brushed off the rotor contact and it seemed OK. There were no rats nests in there...

I checked all the fuses under the hood and they all seem fine.

The Jeep was in a garage while I was gone too if that matters at all.

Any ideas or suggestions where to look next?

Thanks for the time!

- Colin"

Since posting this, I swapped in a known good battery - no change.

I tested resistance on the B and C pin of the CPS and there was none which seems to indicate a good sensor.

I pulled the coil and tested it for resistance and it tested OK.

I pulled the wire that comes off the coil to the distributor and grounded it while trying to start the jeep - there was no spark.

SO - I have no spark going to the distributor, the coil tested OK and the CPS tested OK too. The Jeep still wont turn over but it will crank.

I'm out of ideas and would really appreciate some guidance.

Thanks!

Check for coil flash with a test light. No flash is bad sensor or so.ething, if it has flash then bad coil.

Sorry, but I'm not familiar with testing coil flash - this is my first Jeep. I'll google it.

I should also mention that the fuel gauge and the volt gauge are inactive in the dash.

Take the connector off the coil, put a test light across both terminals of the connector then crank it and see if it flashes. Check your battery cables too.

I swapped in the coil from a running Jeep and replaced the CPS with a new sensor for good measure - no change.

Could the cam position sensor cause the same faults as the crank position sensor (dash indicators not working, no start, etc..)?

I'm trying to remember what the relays are that you'd need to test.

Other thing if it's confirmed to not be getting the signal at the coil but power, the cam position sensor in the distributor might be bad.
Depending what year it might be a PITA to change so I'd test it first.

I'd also double check the battery is good because that it the source of a lot of mystery problems



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ArBrnSnpr said:

... the fuel gauge and the volt gauge are inactive in the dash.

Click to expand...

That is one of the primary symptoms of a faulty Crankshaft Position Sensor or some other type of short circuit on the CCD Bus. One at a time, unplug each of the 5 volt OBD-II engine sensors and re-check the gauges after each sensor is unplugged. When the gauges function correctly you will have a better idea of where to concentrate your diagnostic testing.


Otherwise, if the PCM reboots due to battery or wiring issues, or an extended period of time with the battery disconnected, you probably have to feather the gas pedal until it starts and idles for a bit.

Well - I threw a cam position sensor at it, another coil and cleaned the contacts on the distributor. No dice.

I ran to the local u-pull-it and was lucky enough to find a 97' Cherokee with a matching part number ECU and threw that in and it started right up.

I guess my ECU took a shit while I tried to jump the dead battery.

Thanks for all the help gents!

ArBrnSnpr said:

Well - I threw a cam position sensor at it, another coil and cleaned the contacts on the distributor. No dice.

I ran to the local u-pull-it and was lucky enough to find a 97' Cherokee with a matching part number ECU and threw that in and it started right up.

I guess my ECU took a shit while I tried to jump the dead battery.

Thanks for all the help gents!

Click to expand...

Ah yeah. They can do that. Rare but it happens.


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