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cherokee laredo starting problems

rohme

NAXJA Forum User
Location
COSTA RICA
hi,

I have a 1990, Automatic, 4.0L, 6 cylinders, Cherokee Laredo, new sparks, wiring, rotor. I am having this problem: sometimes it starts and sometimes it cranks but does not starts. It could starts with no problems, drive a while but when I park and try again to start it, it does not starts.

I use a digital meter and read the signal form the computer to the ignition module and it is OK (5v). Some guy told me to replace the device inside the distributor (pick-up) but it did not fix the problem, so I am wondering What could be the problem?

I will appreciate any help.
 
I have a 88 XJ, on our vintage XJs there are two sensors you may be concerned with. The first one you replaced, it called the camshaft position sensor, also called the sync sensor. It is located inside the distributor. This one lets the computer know which ground of cylinders are on the injection cycle.

The sensor most people replace is the crankshaft position sensor (CPS). It is located on the transmission bellhousing at the 10 o'clock position from the driver's seat. If this sensor fails there is no way for the engine to refer the information. It is a truely single point failure. Go and buy a new CPS and install it. The dealer sells two versions of the CPS, there the standard CPS and the high altitude CPS. Buy the High alt CPS, it costs the same and gives you more advance which means more power. Don't worry about knock since your engine has a knock sensor. If you install the high alt CPS and you get engine knock then you need to replace the knock sensor.
 
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