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

rspi · #1 (**permalink**) 11-03-2009, 02:45 PM

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 · #2 (**permalink**) 11-03-2009, 03:28 PM

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 · #3 (**permalink**) 11-03-2009, 03:46 PM

It's a 4.0. What is a CKP?

SteelHeadz · #4 (**permalink**) 11-03-2009, 03:55 PM

Crankshaft position sensor.

rspi · #5 (**permalink**) 11-03-2009, 03:59 PM

Where is that? What does it look like?

rspi · #6 (**permalink**) 11-03-2009, 04:01 PM

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

SteelHeadz · #7 (**permalink**) 11-03-2009, 04:57 PM

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 · #8 (**permalink**) 11-04-2009, 12:10 PM

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

SteelHeadz · #9 (**permalink**) 11-04-2009, 12:25 PM

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

rspi · #10 (**permalink**) 11-04-2009, 03:05 PM

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 · #11 (**permalink**) 11-04-2009, 03:09 PM

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 .

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

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

rspi · #12 (**permalink**) 11-04-2009, 03:26 PM

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

SteelHeadz · #13 (**permalink**) 11-04-2009, 03:38 PM

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 · #14 (**permalink**) 11-05-2009, 08:18 AM

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.