Oil Pressure Sender- Bad Replacement?
 

I was having an issue with my oil pressure - once the car warmed up the pressure would drop to 0 then bounce around when I accelerate. I replaced the OP sending unit but now the pressure gauge pings out as soon as I start the engine. Actually, I don't even need to start the engine - even if I put the car in aux it pings out.

Did I get a bad sending unit? Or is there something else I should look for?

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2000 Grand Cherokee Laredo
4.0 6Cyl

Check the wiring to the sender and make sure it's not grounding out someplace. Also be sure you have a sender for a gauge, not an idiot light.

Also check the connector for dirt or oil. Being a solid state sensor, any difference in resistance can change the guage reading.

Looks like the connector is a little grimy. It was dark when I got to check, but I think there might even be some oil in there. What's the best thing to use on that? Is brake cleaner OK?

I'd use a good shot of WD40 as a detergent, then plastic safe electrical cleaner spray to actually clean it.

If I could have kept the money that WD-40 has made me through misuse...

"WD-40" means "Water Displacer, formula 40." Its primary ingredient is fish oil. It was formulated to protect shop stock and raw steel parts against atmospheric corrosion - and that's about the only thing I'll use it for!

Brake cleaner or electrical contact cleaner for the connector, toothbrush for difficult crud. If absolutely necessary, you may reterminate it (it's usually a regular 1/4" spade lug,) but make sure you're connecting to CLEAN wire and seal the connection once you're done.)

And please stop thinking that WD-40 is a "miracle in a spray can." I've made a lot of money over the years cleaning that crud off of places where it wasn't supposed to be (usually electrical and brakes.) About the only other use I have for it - beyond protecting shop stock - is as a light-duty, need-it-now, cutting lubricant for mild steel or aluminum (and, that's only when I'm out of kerosene, which works better, and I don't have any Diesel handy, which is related to kerosene.)

I'm with you there, 5-90, I just think EVERYBODY has a can of WD-40 around and it does loosen up crud. I've used it for drilling or saw cutting also in a pinch. Actually I like CRC 5-56 better, but can't always find it. My friends and I have used kerosene for decades for heavy part cleaning, followed by a garden hose washdown. We started this when kerosene was 5 cents a gallon. Being a toolmaker, we used kerosene for machining aluminum, until OSHA said it was a fire hazard. Since then, EDM oil works well. it has a higher flash point.

BTW, the sensor on my WJ is 3 terminal solid state and when it broke, it had a circuit board inside. I think it's a piezoelectric crystal. Quite touchy, resistance wise.

If you absolutely must use WD on electrical contacts, I would recommend cleaning it off with brake cleaner or contact cleaner and use a toothbrush to loosen it up.

I prefer to dry-clean contacts where possible, a rubber eraser works neatly.

Where is this connector at? My 98 XJ does te same thing as soon as I turn it on.....pinged to the right!

On your 98, it should be right beside the oil filter. On my WJ, they changed the filter location, now it screws directly into the block and the pressure sensor was moved to the passenger's side rear corner of the block. The guage going to full scale was the reason I changed mine. If it's 3 wire solid state, I would recommend buying nothing but Mopar replacement.

Acrosley, did cleaning resolve the issue for you? The reason I ask is I've recently purchased a 2000 GC 4.0L and have developed a Oil Pressure Gauge issue that seems to come and go. I was thinking sending unit but it looks like I need to check and possibly clean the unit and connections first (?). I'll probably wind up posting my own thread on the matter (new member), but wanted to check the forum first. I hope your issue has been resolved. Thanks!

Yes the "dummy gage sensor" will cause the gage on a 2000 to read full scale. How much did you pay for the sensor? The dummy sensor is cheap, less than $20.