[dadstjaz]

Was wheeling last night, half tank of gas and it slowly sputtered to a stop (4.0) tried to restart and ran like it was starving but have great line pressure, spark is great at the plug. eventually would not start at all but cranks great with no noises from the top end so have ruled out Timing Chain jumping, was thinking maybe Crank Position Sensor. Throwing code 12 and 55. 97 TJ 4.0 Manual

ANY IDEAS

[0lllllll0Hullen]

possibly o2 sensor.

[dadstjaz]

Raplaced all 3, 5 years ago

[dadstjaz]

Anyone know how I can test the sensors with a meter?

[dadstjaz]

Anyone??? Please!!!

[Jonny Jeep]

The codes are nothing to help. 12 - battery disconnected within last 50 key cycles. 55 - end of codes.

When you say half a tank of gas how do you know? The fuel senders we have can go bad and read more fuel than is in the tank. I've ran out on the motorway when my sender went bad, with more than a quarter of a tank showing. Lucky for me it was at an exit with a gas station nearby. My sender was replaced under recall.

If you have spark your cam and crank sensors, and your coil are good. The only thing that should stop it starting is lack of fuel or air. I'd stick a gallon in the tank and if it starts go fill it up and see how much it takes to fill it.

[dadstjaz]

Thanks for the help. How do I know Half tank? 65 miles from full tank, when it died I put my five gallon Jerry can of fuel in thinking that the of angle caused it not to pickup, checked air filter on the spot, good shape, checked for spark at the plug wire, good and bright, then removed the rear most plug (easiest) to see if fowled, good with great spark. Don't know what the #'s are on the fuel pressure, but had plenty. Did the computer reset thing, disconnect for about a minute with the terminals touching to drain any current, then reconnect, and headlights 3 times. Checked ALL fuses (under hood and dash). Did all this on the spot on the trail..Thankfully I was with a great group of wheelers (5 FJ's and 5 Jeeps) I got towed 40 miles home by a Toyota FJ, (how embarrassing) With all this info , which should have been in the 1st post, ant new idea's? I'm leaning towards the CKP Thanks for taking your time to think about it!

[Jonny Jeep]

As you have a good spark I'd still be leaning towards fuel.

Fuel pressure should be 49.2psi give or take. If you are getting spark the CKP and CPS should be OK. The coil and injectors both get power from the ASD relay and are grounded individually by the PCM. Might be worth checking for voltage at the darkgreen/black wire (from the asd relay) at the injectors That's the same 12V feed to the coil. Also check the connections at the PCM.

Coil resistance should be 0.95-1.2 ohms at the primary and 11,300 to 15,300 for the secondary HT side.

Crank sensor test. with sensor unplugged Place an ohmmeter across terminals B and C. Ohmmeter should be set to 1K-to-10K scale for this test. The meter reading should be open (high resistance) . Replace sensor if a low resistance is indicated.

[dadstjaz]

This is the tester and the test being performed on the CPK, don't know if the tester is set right, any help would be great. Also how do you test the ASD, and where is it? Also how do you test the coil, this is my daily driver and not alot of $$ available.

Went and got a new CPK and tested the same as the old, did not start the Jeep.

THANKS

[Jonny Jeep]

Interesting it didn't show open circuit but is still good. Crank sensor test was directly quoted from the factory service manual. I did say that cam and crank sensors should be good as you were getting spark.

ASD (auto shut down) relay is in the power distribution center (PDC) near the battery. If you have spark the relay is good and voltage is getting from the relay to the coil. The ASD relay (and the fuel pump relay) both energise for two or three seconds when the ignition is first turned on, then again when the engine is cranking or running.

If the fuel pump relay is OK you will hear the pump prime when the key is turned on. The ASD and fuel pump relays are the same as the horn relay so they can be swapped about to try and see if they are faulty. Try swapping them into the horn relay position and if the horn works the relays are OK.

To measure the coil resistances disconnect the plug and measure primary resistance between the contacts that the dark green/black wire and the grey wire go to. Secondary resistance is measured between the dark green/black wire contact and the HT output.

[dadstjaz]

Just did the relay swap, all are good. And just because.....I checked my fuel rail pressure...0.0 No pump actuated, so tomorrow will crawl under and see if a ire got pulled loose or if the pump is bad.....God I hope it's just a wire. Just put 5 inches of lift on and this was my shakedown run... guess I shook it down. Will update tomorrow. THANKS for all your input..learned things that will be valuable in the future...

[Jonny Jeep]

Hope it's something simple like that. Wire that supplies power to the fuel pump is dark green/white. ground wire is black. The other two wires are for the fuel level sender.

[dadstjaz]

Jeep is running fine, the wires got pulled out of the plug harness for the fuel pump. all is well, back to the trails WOOT WOOT

Hey guys thanks for all the input.

Troy