1999 TJ Sahara Crank No Start

[RobbieT]

135000 miles. Cranks but no start. Has fuel gauge and volts showing on dash, tach doesnt register when cranking dont know if its supposed to. I installed new coil and distributer (the old one was probably fine but wanted the new cam sensor distributor pickup coiland figured new cap and rotor wouldnt hurt). Didnt find TDC just put it in the same orientation as the last one. Tried a different crank sensor that had worked previously but no go. Sprayed some flammable carb cleaner in throttle body no fire. Haven’t tested fuel pressure but i hear fuel pump come on nice and smooth when i turn key on. Squirts at the schrader valve after cranking and pushing little button at valve. Charged up battery cause of all the cranking



I have a multimeter but havent brought it home from work or started checking voltages yet.



Before i changed parts this go around wife said Jeep started sounded like crap so she turned it off then wouldnt start she cranked it about 5 times and gave up. I came home and cranked on it for about 5 seconds then pushed gas pedal to floor and it started and drove fine for 2-3 days then it wouldnt start and there it still sits. At least it was in the driveway. It was pretty cold when she started having problems and crapped out like single digits.



Had problems last winter turned out to be ignition switch. Changed fuel pump in the process delphi brand installed. Also installed new battery one year ago. Took it on some great adventures.



Maybe 3 years ago had problem with crank sensor no start died on side of road replaced with local parts store brand and eventually installed a mopar crank sensor. Ran great.

 

[Rickyd]

Spark? Are the injectors getting pulsed?

 

[RobbieT]

Spark? Are the injectors getting pulsed?

Thank you! Put a spare spark plug in a wire and grounded to motor mount no spark. Fuel rail ticked when turning ignition on. Tick tick ticked when cranking.

 

[b1uj33pbr3w]

One thing you should try is to see if the coil ground is being interrupted like it should.

Take a test light and turn the power of the jeep on.

Put the test light on the negative side of the coil, it should light up on both terminals (if it does not, fix that). While doing this, you will need to have someone try to start the jeep. Remember when starting to keep the test light on the negative side.

What you are looking for is for the test light to flicker. The flicker will be obvious. If it does not flicker then the coil is not getting its circuit cut intermittently and there there coil won't fire.

I'm new to the jeep world but this is how effectively all distributor based ignition systems work. If you do not get the flicker we will need to research what is responsible for for creating that break in the circuit. With old cars this was done with ignition points. Early fuel injection would use a ignition module module for this. My jeep is a 2000 and I have not looked into it but I'll try and do some research as well unless someone comes with the answer.

 

[b1uj33pbr3w]

One thing you should try is to see if the coil ground is being interrupted like it should.

Take a test light and turn the power of the jeep on.

Put the test light on the negative side of the coil, it should light up on both terminals (if it does not, fix that). While doing this, you will need to have someone try to start the jeep. Remember when starting to keep the test light on the negative side.

What you are looking for is for the test light to flicker. The flicker will be obvious. If it does not flicker then the coil is not getting its circuit cut intermittently and there there coil won't fire.

I'm new to the jeep world but this is how effectively all distributor based ignition systems work. If you do not get the flicker we will need to research what is responsible for for creating that break in the circuit. With old cars this was done with ignition points. Early fuel injection would use a ignition module module for this. My jeep is a 2000 and I have not looked into it but I'll try and do some research as well unless someone comes with the answer.

Ok I just looked into it and I'm slightly off here. However if you look at page 283 (section 8D) in the 1999 service manual it outlines procedures for testing for this. The ECM also has a bit of a role to play here as well

 

[Jerry Bransford]

The tach is driven by the crankshaft position sensor. The engine won't run and the tach needle won't rise up when the crankshaft position sensor is bad.So that part would be my first strong suspicion.

Unless you can afford the Mopar, which would be my choice, I'd go for the Standard Motor Products PC176K on the below link. At least make sure it's for an automatic like you have. Or go to NAPA and get their best/premium replacement which would be better than a store brand like Duralast from Autozone. Avoid store brand sensors!

And by the way since you have the 4.0 engine, your automatic is the 32RH. The 30RH you show in your Profile only come with the 2.5L four-banger.

https://www.rockauto.com/en/catalog...1777,ignition,crankshaft+position+sensor,7196

 

[RobbieT]

The tach is driven by the crankshaft position sensor. The engine won't run and the tach needle won't rise up when the crankshaft position sensor is bad.So that part would be my first strong suspicion.

Unless you can afford the Mopar, which would be my choice, I'd go for the Standard Motor Products PC176K on the below link. At least make sure it's for an automatic like you have. Or go to NAPA and get their best/premium replacement which would be better than a store brand like Duralast from Autozone. Avoid store brand sensors!

And by the way since you have the 4.0 engine, your automatic is the 32RH. The 30RH you show in your Profile only come with the 2.5L four-banger.

https://www.rockauto.com/en/catalog...1777,ignition,crankshaft+position+sensor,7196

Thanks for the input. Is there a way to test continuity of crank sensor wires to the pcm connector? Going to bring multi meter home from work toworrow. It has a mopar crank sensor thats a few years old in it. I ordered new crank sensor from Rock Auto just in case came with new connector and wires. Also read up on service manual some thank you.

 

[Rickyd]

Thanks for the input. Is there a way to test continuity of crank sensor wires to the pcm connector? Going to bring multi meter home from work toworrow. It has a mopar crank sensor thats a few years old in it. I ordered new crank sensor from Rock Auto just in case came with new connector and wires. Also read up on service manual some thank you.

We have some factory service manuals in the resource section. Study up and then unplug the cpk and ecu plug. Ohm out the different wire runs. Pay very close attention to the connectors and pins to make sure it isn't a loose connection. The worst is when its intermittent and you need to shake the harness to find it

 

[RobbieT]

I tried a different crank sensor i ohmed out crank and cam sensor wires and had good continuity. Im shipping off my PCM to wrangler fix.

 

[RobbieT]

Resolution!!! WranglerFix repaired my PCM. I installed and the Jeep fired up! Thanks to all the forum members that helped and happy wheeling!