Different oil pressure problem...

OK, here's apparently a new one (couldn't find it with a search). Does your oil pressure gauge read zero when you turn the key on but don't start the engine? My oil pressure needle only drops to zero when I turn the key off. Turn key on and all the gauges come to life and oil pressure immediately reads about 35. My XJ has the oil-pressure-drops-to-zero-at-idle problem that almost everyone seems to have, buy mine drops to 35 at idle. It's starting to bug me and I was wondering if anyone else has this problem and if they've fixed it. I read that you can't just pull the needle off, so I can't just move it to read zero. Any ideas? BTW, it's a 2000 XJ 4.0.

engine not running = no pressure.
As for low pressure, live with it. I have a 98 and it does the same thing, it bothered me so i installed an auto meter pressure gauge on the pillar pod.

>engine not running = no pressure.

I realize that, but does no pressure = 35 PSI on the gauge? When power is running to the gauge, the gauge reads about 35 unless the engine is running. At idle when at operating temp, I'm reading 40 (until it drops to 35 and my check gauges light comes on). When I turn the key off and kill power to the guage the needle drops to below zero as it should. Turn key on, gauge goes to 35. Start engine and get to operating temp, gauge reads 40.

>As for low pressure, live with it. I have a 98 and it does the same thing, it bothered me so i installed an auto meter pressure gauge on the pillar pod.

The low pressure problem I'm still working on. Mech gauge verifies factory guage (except for difference in starting point) and I've replaced the oil sending unit. Colder temps making the oil thicker is helping since I only have a 15 min drive to work.

Hi, I'm new at this forum. I have a 2000 XJ that have the opposite problem. My oil pressure gauge max out all the time and when the truck is turn off it goes to 0. Anybody knows what's going on? Please help, thanks!

Its because you broke the oil pressure connector, the oil pressure switch sending unit (or both) or the sending unit (sensor) is just shot. That or you had idiot lights and swapped to a gauge cluster w/o getting a new sending unit. An open circuite reads max oil pressure on the gauge for your year. You will probably need a new sensor (specify that its for gauges not lights at the parts store). Its common for them to break when changing your oil due to its vulnerable location above the oil filter.

This will help you EVOKIN. http://www.olypen.com/craigh/pressure.htm Hasn't helped me. It's like the needle isn't pointed where it's supposed to. If it didn't drop down past zero when the key is off, I'd pull the needle and just adjust it. Oh well. Guess I'll just live with it.

djwright4341 said:

>engine not running = no pressure.

I realize that, but does no pressure = 35 PSI on the gauge?

Click to expand...

Obviously, no pressure = zero.

Disconnect the wire from the gauge with the ignition on (engine can be running or not, doesn't matter). With the wire not touching anything, the gauge should swing all the way to one extreme (which way depends on year). Then ground the wire directly to the engine block, bypassing the sending unit. The gauge should then swing all the way to the opposite extreme. If it fails to go to both extremes, you have a bad gauge. Otherwise, you have a bad sending unit.

Thanks for the help!