2000 XJ Classic, 4.0l, 156,000 miles
While I'm still trying to identify my problem with the on/off number 2 cylinder injector problem, out of nowhere the oil pressure gauge goes zero. I was testing the #2 injector plug ground wire at the ECU. The oil pressure was fine. Restarted the engine to test the pulse at the ECU, no oil pressure, Like Zero. Checked what I could find on the forum and most posts pointed to a faulty oil pressure sending unit. Bought a new sending unit and started to install. Found that the three wires to the sending unit plug were pair wires for about and inch before the plug. I wrapped the bare wires, installed the new sending unit and presto, no change, meter still reads zero. I could sure use some help. I would like to drive the XJ, but I can't get past the issues. Lots of thanks to all the folks that help the morons like me.

 

Sure you didn't short anything out during your works?

Do a gauge cluster (dashboard oil gauge) self- check first
Then I'd verify oil pressure with a gauge

 

Thank you for the response. I don't know if the sending unit plug wires shorted out. I have seen a youtube were the wires to the plug looked like mine. Is this a common problem?
I did the gauge cluster self-check and the oil pressure gauge tested correctly.
I plan to pick up an oil pressure test gauge on Monday. I'll report back on how that works out.

Once again, thank you for the info.

 

I had a low oil pressure in my 98 with rough idle and occasional stalls when idling, looked around on the forum and couldn't decide which path to go down, looked on Youtube as well. A few days later, the oil pressure went high with the same rough running condition. Decided to change out the oil pressure sensor, sending unit, switch (everyone called it something different). Bought mine at NAPA (Part #: NOE 92603971) for $24.99. Seemed to work but then started showing a consistently high pressure i.e. 30 at idle. Someone at NAPA told me to be sure to change the air filter as well, so changed the air filter since mine was pretty dirty and the oil pressure came down to normal operating range. Not sure how all that is tied together but do know that there is an air line that connects from the air filter box directly to the top of the valve cover bypassing the throttle body.

 

Just a sidenote: It's actually not bypassing the TB as such. The direction of flow through that tube is the other way and actually meant to 'recirculate' back through the TB/intake
If your airfilter gets contaminated with oil blowby, it's through that tube that that happens..