my oil pressure gauge sometimes goes to 0 and the oil light comes on. Then it will go back to normal. Engine runs perfect. Is the oil sending unit going bad, and if so where is it located? Anybody else had this problem?

 

Assuming from your "sig" we are talking about a 1996 XJ6 (X300), and if so, the oil sender is my best bet.

It is located up on top of the oil filter housing, and real easy to get at, NOT, you cant even see it on mine. So I reckon throttle body off to even stand a chance.

Now I may be wrong, and others will certainly correct the staus if that is the case.

 

thanks!

 

Changed mine (1995 VDP) last Saturday. The Jag "fix kit" is an oil pressure switch (7-8 psi set point) and a jumper harness containing a resistor. TSB says to reprogram the instrument pack but that is unnecessary. Your guage will go to the middle (40 psi) and park when running, regardless of rpm, as you are replacing a transducer with a switch. I guess the "reprogram inst. pack" step is what gets you the exact middle, as mine (not reprogrammed) goes to about 47 psi...a little over halfway. The kit is available on eBay and several auto parts sites for $49-$60. I didn't try not using the resistor/jumper to see where the needle falls but that may be an option if you can't find the kit, only the press. switch. Key realization is that your guage is now really just a light, so it really doesn't matter what the pressure is reading as long as it comes off the "0" peg.

I read a post on one of the forums, possibly this one, but can't remember now, where someone went in from the top side. I have the plastic ramps and once you conquer the problem of them sliding across the garage floor as you try to drive up, it is a much easier access from underneath vs. anything I could find from the top. Hex is allegedly 11/16" "British Standard" but was advised 18mm would work, even shown so on an old 2V XJ40 engine in the shop floor. Spent the morning at PeeWee football scrimmage, then went out and bought 18mm spanner of finest steel CHina has to offer along with small copper-sweater's propane torch. Clamped it up in vise and started heating in an attempt to put an offset on the open-end similar to that found on the box-end. Many heat-n-hit cycles later, where the hammer hits became progressively harder, I had a suitable tool, so I thought. Despite the angle being near-perfect, I just couldn't fit it to the hex. Finally, I tried an el-cheapo adjustable wrench I had laying around and it would open just wide enough to fit. No possibility to use it for dismount though as the handle was hard against the block, the starter motor was in the way, and the only way it had room to fit was in the "tightening" orientation. Comparing that opening to my "Sunday Spanners" that I had no desire to heat/bend, I decided 19mm was a better match. Back to town to get a bendable copy and repeat the previous process. However, guess I got impatient and didn't heat it properly as I broke this one off right at the open-end, leaving no shank whatsoever. The remaining piece was enough to confirm my guess as to 19mm fitment. Not being keen for another trip to town and another $10+ wrench, I clamped up el-cheapo adjustable and started the heat-bend process again, this time with greater success. This allowed me to fit it in the proper direction to loosen the transducer and the angle let the handle clear the starter motor, but left very little moment arm resulting in handle cutting into palm without breaking transducer loose. Leather gloves helped but didn't resolve the problem. Finally, I slipped an 1/8" pc. of flat steel into my glove between my palm and spanner and effected the removal. Installation was straightforward from there on. The TSB allots 0.95 hrs. including time for reprogramming the inst. pack, whereas I spent all afternoon on it. Guess there's a reason I work in an office, if this was my livelihood, I, and several of my 5 kiddos would probably go hungry many nights....
Best of luck with it. Another option is to destroy the top of the transducer with pliers so you can fit either the box-end spanner or a socket on it, but to me, that would be possibly converting a good, serviceable car with an indicator problem into an oil-spurter that I'd have to have hauled to someone competent to fix if I failed to get it loose after destroying it....

 

as GF said, it is located left side, adjacent to oil filter, has a single wire attached to the top.

 

I've got this problem. I was really going for it and notice zero oil pressure and oil warning light. I thought; oh no I've killed my car. So I slowed down and looked for a place to leave the motorway and then it all went back to normal, instantly. I only ever have one oil pressure reading, just below middle. The car was fine the whole time.

I see that it does this sometimes. It seems to be when going fast. I am assuming a dodgy connection and hoping I don't have to change the sensor.

I see the post where the chap spent all day bending spanners to get the old one out. What have others done?

 

If you are looking to replace the oil pressure sender on the 4.0, its probably the easiest thing you will ever do on this car. There is another thread somewhere, I think i used a 21mm socket and it literally took longer to jack up the car. If you are quick, you'll only get a few drops of oil leaking out.

 

I think I may have jumped the gun. I assumed that the gauge actually showed the amount of oil pressure, which of course would never go to zero unless the engine was wrecked, which it's not. However now I know that the oil pressure light and the gauge are connected to a switch I can appreciate what's going on.

I checked the oil and it's below the bottom of the dipstick!
It just needs more oil and the light was simply telling me this.
It's a bit naughty of them to feed the gauge with fake data though. It sent me down the wrong path. British engineering.

 

Not all of them are like this! The early production X300's have a real oil pressure sender and gauge.

 

It's a real gauge on the dash just fed with a resistor to set it in the middle. I wonder how simple the conversion would be?

 

Up to engine number 134019 it was a transducer, after that the resistor link. Apparently, there was some sort of reprogramming of the instrument pack needed to make use of the resistor. Not sure that it is reversible.

You'd probably need the instrument pack from an earlier car and the transducer on the oil filter head.

 

No, it's not that important. I just thought if I was replacing the transducer I could get a better one that would make the gauge work. Thanks.