2004 Grand Cherokee 4.0 cranks but will not start...

[rspi]

Long story or short. Well, I'm at work so here is the short...

I have a 2004 Grand Cherokee Laredo with 93,880 miles on it that will not start. I parked it at the office, went to leave 4 hours later and it will not start. It cranks well, but won't turn over.

I can NOT hear the fuel pump so I replaced the relay, still no start.

I hooked up my cheep OBD-II code reader and I get an error message that it will not link to the computer. So I ordered a "programmed computer" and it still does not start. Just cranks and cranks and cranks...

What should I try next???

 

[SteelHeadz]

4.0 or 4.7? Check for fuel and spark. Usually if there's no spark on a 4.0, the CKP is at fault and will also shutdown the fuel pump circuit from the PCM. Any other symptoms?

 

[rspi]

It's a 4.0. What is a CKP?

 

[SteelHeadz]

Crankshaft position sensor.

 

[rspi]

Where is that? What does it look like?

 

[rspi]

Should I get one from the dealer ($110) or NAPA ($54)?

 

[SteelHeadz]

Before you spend money on it, verify that there is a DTC for a "CKP signal not received by the PCM" . The CKP is located on the upper section of the bell housing close to the engine where the starter ring gear on the flexplate. It's black in color with a wiring harness coming out on top of the sensor. Usually held in place with 2 bolts. When you get the new one, it might have a piece of thin card board on the tip of the sensor..Do NOT remove the cardboard. Install the sensor as is. It's there for the proper airgap of the new sensor.

 

[rspi]

Well, as explained, my code reader will not read the computer. I guess a DTC is a code from the OBD-II reader???

 

[SteelHeadz]

Yes, a DTC (Diagnostic trouble code) is a code from the PCM.

 

[rspi]

Can not read the PCM. So I want to install this Crank Shaft Possition sensor... Where is it? I hope it's not between the motor and the fire wall. If so, how in the heck do I replace it???

 

[SteelHeadz]

The Crankshaft Position (CKP) sensor is mounted to the transmission bellhousing at the left/rear side of the engine block .. The sensor is adjustable and is attached with one bolt. A wire shield/router is attached to the sensor .

1. Disconnect sensor pigtail harness (3–way connector) from main engine wiring harness.
2. Remove sensor mounting bolt.
3. Remove wire shield and sensor.

1 - SLOTTED HOLE2 - CRANKSHAFT POSITION SENSOR3 - WIRE SHIELD4 - MOUNTING BOLT5 - TRANSMISSION HOUSING 6 - PAPER SPACER

 

[rspi]

Ouch! From what I can tell, I can not get to this part unless I pull the motor or drop the transmission. Dang!

 

[SteelHeadz]

You need not pull either one out to get to this. I found it easier from under the vehicle to get to this sensor. I used a long extension and a wobbler socket.

 

[rspi]

And the winner is (drum roll please), Crank Shaft Position Sensor.

Again, the symptoms:

1. Will not start.
2. Can not hear the fuel pump when you try to start.
3. Can not read the computer with the OBD-II code reader. Will not connect or communicate.
4. (Not sure about spark or fuel - my guess is have spark / no fuel).

Not a DIY job, just not enough space for me to reach the part to replace it. A local Jeep mechanic was kind enough to use my NAPA part and did the job for $113.