Khawk2

This is my first post and this issue may have been covered previously but I did not find this information so I will post hoping it will help others.
Sorry but this is a little long.

The problem started when I noticed that the oil pressure gauge on my 97 GCL 4.0 was showing about 30 psi with engine running at idle and with engine not running and ignition on. With ignition off the gauge dropped to 0. Running on the highway hot it showed about 50 psi. The diagnosis began.

I put a mechanical test gauge on and found about 58 psi at idle cold and about 35psi hot at idle. Pressure fluctuated as expected with rpm changes.

I purchased a replacement sender from a local supplier (O'riely) and installed. No change 30 psi with ignition on engine not running. Used contact cleaner on connector at sender, firewall connectors, back of gauge cluster connector, removed gauge from cluster and used contact cleaner on mounting screws to PCB in gauge cluster and re-mounted gauge. No Change.

I purchased another replacement sender from NAPA and installed.
No change.

I checked the ground wire on the sender connector to negative post on the battery..0 ohms..as expected. Checked voltage from gauge cluster at sender connector to ground, 5.138 volts. With the sender disconnected the gauge showed 0 psi. With the signal wire at connector jumped to ground the gauge showed 80 psi as expected.

Today I picked up an OEM sensor from the local jeep dealer (p/n:56031003-AB sensor OI $63.70) and installed. Problem solved.

While I provided accurate model year and engine information to the local after market suppliers, there must be a difference in the resistance range of the OEM sensor for the 97 GCL model. The parts person at the jeep garage said this sensor is only for the 94 thru 97 4.0 liter engine.

For me this adventure lasted about four months. I hope this information will help save others with similar problems time & $ and help them make a quicker repair.

I appreciate this forum and the information it provides to the jeep community. Thanks to all.

dave1123

Welcome to CF and thank you for the info. I had a similar problem with my WJ 4.0 in that the gauge would peg at 80 psi as soon as the engine fired up and stayed there until you shut it off. I bought a NAPA Premium sensor made in Mexico for $49.95. It read 30 psi all the time regardless of engine temp. Well, it read 40 psi when it was -15* outside! I bought a OEM Mopar part from my dealer for $70 and it reads properly, 55 psi cold start, 40 psi hot idle, and 55 at anything above 40 mph.

When I took the original one off the motor, I broke it. Inside I saw a printed circuit board with a piezo-electric crystal to measure pressure. I assumed manufacturing tolerances are critical to it's proper function. Enough said.

dschappell

My WJ has been doing this for the past while as well. Didn't know what the problem was though. The shop told me "ahh it's ok"... Yeah ok. Thanks for the info!

dave1123

Believe me, I don't like going to the dealer for parts, but it looks like you have to with jeeps. I resisted until the guys here convinced me. I even use Mopar oil filters now.

Just one other thing. I finally broke down and bought Rain-X wiper blades at $16.99 each. They work the best of any I've tried so far. Further results after I see how the work with snow.