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CPS Question

Black_Black

NAXJA Forum User
Location
Colorado
Have an 89' cherokee with a no-start issue. On crank it will try to fire for half a second but no dice.

I've installed a few CPS sensors, and they are not reading any spikes on AC voltage but it could be my multimeter. Renix Engine Monitor does say CPS fault.

Is there anything that would be keeping the sensors from reading? The original was gunked up. Is it a bad idea to pressure wash through the hole in the bellhousing? Next I am trying the 3/8" hole mod that cruiser suggested. Any ideas welcome
 
Just tried another CPS, and borrowed a different multimeter to be sure. No spike, 0.0 on crank. Any ideas?

I'm going to make sure the flexplate is still there
 
I would stay away from the pressure washing idea... There is an OEM plastic type plate that is supposed to cover that hole and leave just enough room for the pigtail connector to fit through. Not only is it not meant to introduce that amount of water, but pressurised..? Trying to help keep your thread alive a bit.

I just copied my post from a similar thread. (Doesn't sound like your specific case completely)
If you don't follow "DEXj's" or DexJeeps... wtv he goes by.. mentioned how these things get heat soaked very easily. I always have issues with that on my 89 MJ. Even have an access panel in the transmission tunnel for ease of access. Take a bottle of water and poke a hole in the top. Spray it down and try to let things settle for a moment. IMO the CPS on these things is just a very bad design. Besides the heat, it gets SOAKED in oil if you haven't noticed. (Magnetic sensor vs oil... not a good combo) Don't forget it might be something as stupid as the pigtail connector on the harness. Everyone has their opinions there. You decide if OEM connection will be kept. Wish you luck.
 
You should not be measuring in A/C current, only DC. You should give a light detection tool a go if you are measuring pulses (ppm)
 
It's an 1989 XJ. The CPS sensor used with the Renix ECU is basically just a coil generating a/c pulses. Later sensors had 3-wires for power, ground, and a signal wire that generates DC square pulses.
 
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