So many things can cause your Jeep 4.0L SUV not to start and the crank sensor is one of them.
Now, to make sure that the Cranks but Does Not Start problem is truly due to the crankshaft position sensor... you need to test it, and in this article I'll show you how to do it with a multimeter in Volts DC mode and without taking it off your Jeep.
In case you're needing a resistance test of the crank sensor, I hate to tell you that one does not exist. The crank sensor on your Jeep is a Hall Effect type sensor and it can not be tested by a simple resistance test.
Don't let this stop you from reading this article... because the test I'm gonna' show you is very easy and is done in Volts DC mode on your multimeter.
Contents of this tutorial:
You can find this tutorial in Spanish here: Prueba Sensor de la Posición del Cigüeñal (1994-1996 4.0L Jeep) (at: autotecnico-online.com).
Tools You'll Need:
- Jack Stands
- 1/2 inch Ratchet Wrench
Important Tips And Suggestions
TIP 1: The crankshaft position sensor test I'm gonna' show you here is an On Car Test. Although, the photos in this article show the crank sensor out of the vehicle, I've photograph the crank sensor out of the vehicle just to make it easier to explain the test.
TIP 2: To perform this test and get a very accurate result you can trust, I'm gonna' ask you to crank the engine by hand. This is super important, because if you use the starter motor to crank the engine- you're not gonna' get an accurate result.
By cranking the engine by hand, I mean turning the engine using a 1/2 ratchet wrench and an appropriate socket on the crank pulley.
TIP 3: One of the most important things to keep in mind, when testing the crank sensor on your Jeep, is that if you have tested for spark and you are getting spark... then the crank sensor is OK. A spark result tells you that the crank sensor is doing it's job. In a case like this (where you're getting spark), this test will not help you.
This also means that you should test for spark first.
TIP 4: The color of the wires (in the image in the image viewer) may not match the ones on your particular Jeep. This is no cause for concern... as long as you keep in mind that the connector locking tab is on top (in the photo), the circuits (wires) will be the same.
Circuit Descriptions Of The Crank Sensor
The crankshaft position sensor, on your 4.0L Jeep equipped SUV, is a Hall-Effect three wire crankshaft position sensor. What this means: it produces an On/Off DC voltage signal that can be easily measured with a multimeter, an oscilloscope, and even an LED light.
Each one of the three wires that connect to it have a specific job to do. One delivers power in the form of 5 Volts from the PCM. Another delivers ground. This ground is provided inside the PCM, too. The last remaining, delivers the signal, that the CKP sensor creates, to the PCM.
The most important thing to know, is that if the CKP goes BAD, your Jeep vehicle will Crank but Not Start.
|Crank Sensor Circuit Descriptions 1994-1996 4.0L Grand Cherokee|
|1||RED/LT GRN||Crank Signal|
8 Volts (1994-1995)
5 Volts (1996)
|Crank Sensor Circuit Descriptions
1994-1995 4.0L Wrangler