Oil pressure light (again) grrrrrrr

Walmart just emailed …transducer is ready for pickup!

Well here it is and it sure looks good to me. Very well built.

One conundrum though, our cabin gauges register 0 to 8 bar AFAIK and this unit is stamped 0 to 10 bar …any ideas on how this will register on the gauge? high or low?
I dug through the spares bin and found a LMD3325BA resistor. Does anyone think I might need it with this unit?


Well after much consternation, the new sender is in place. The cabin gauge no longer registers zero and the oil-can icon is out.

Not all is hunky dory though. :face_with_raised_eyebrow:

It seems I’ve just learned more than I ever wanted to know about oil pressure transducers :roll_eyes:

To this point my only concern was whether or not the gauge would max out or read too low …BUT …now I find there are different types of transducer/gauge pairings.
“European style” (e.g. VDO) transducers register on the gauge using an ascending resistance value, i.e.
0 bar -resistance is ~10 ohm and at 10bar -resistance is ~185 ohm

Now “American Style” (and presumably XJ40 style!) work in the opposite way, using a DESCENDING scale, so high resistance = low oil pressure and low resistance = high pressure.

So what does that mean in reference to my new sender? Well cruising speed registers about 6 bar and as I slow to idle the gauge rises to max. At least I don’t have the oil can icon lit!

So, I have to find a “non-european style” sender and do the job all over again.

I guess if a job is worth doing, it’s worth doing twice, eh?

I start from a position of knowing nothing about XJ40 OP senders, but I am very familiar with the travails of the predecessor for XJ motors being unreliable, and in the end I simply gave in and added an aftermarket matching EVO digital sender and gauge

I also fitted a thread adaptor

Now for the last many years I have dead accurate OP readings

I also added an original idiot light sender via the OP gallery (which was not fitted to my engine)

Thanks for the lesson in Oil Pressure Transducers 101, that will save some of us from a similar fate to yours. Inquiring minds want to know though - what method did you use to R&R the unit?

I went in through the front Mike, removing the air pump. It was fairly straightforward getting the 3/4" crowfoot on to the old sender, although did find out not all 3/4" crowfoots are the same! The one in the shop was quite beefy and would have required grinding down and the type I had in the car toolbox were semi-open end or “part-ring” so couldn’t slide onto the fitting. Found a set at Princess Auto that were just the right thickness, $19.95.

Once the sender was loosened 1/4 turn it spun off easily by hand. Re-tightening the replacement with such limited access was no fun though, indeed a real pain.

After reattaching and plumbing the air pump I started the car and guess what? No oil pressure! The connector had gotten pulled off the sender when wrestling and routing the air pump hoses. Oh Joy!

So this was a challenge. There was literally no way to get my hand back in there to reattach the lead. I jacked up the car and tried from under but it couldn’t be done, at least I couldn’t.

Eventually I removed the air filter, MAF and the TPS plug mount and was able to squeeze my arm in and replace the connector. Scratches on my arm are healing nicely this morning.

So - I do not recommend replacing the sender from the front on a 94MY XJ40 and the next time (which will be next week) I’ll yank the intake plumbing/throttle body and do it properly. Lazy man’s approach not always best, hence consternation!!

Larry, T:hanks for keeping us filled in on this PITA project and your research. Now could you advise us of the part number and source you settled on that gives you the correct readings on the gauge.

John, I’m not sure the new unit will operate exactly as OEM - it may require a resistor in the circuit like the previous aftermarket units that were selling a few years back. They read a bit high and fitting (what I THINK was) a 75Ω resistor inline brought them into the correct range.
The unit I ordered was the ÜRO C46272 which is listed as the Jaguar replacement from 81 to to 92. 6 and 12 cylinders, XJ6’s and XJS’s. I suppose the 93 and 94 models get the idiot switch recommendation?

Anyway, that’s what’s on the way. It’ll be here in a couple of days but I think it’ll be next week before I have the gumption to try the job again!!

Larry my friend …

I enjoy keeping my XJ40 as original as possible, but on the other hand I have also enjoyed modifying my car to become more user friendly …

Modern stereo
Steering wheel controls for my modern stereo
Ski slope cup holder
Garage and gate opener controls in the overhead console
Elimination of the quirky passive seatbelt system (safety issue)
Elimination of the bulb failure warning system (sanity issue)

… and of course replacement of my always troublesome oil pressure transmitters with an Idiot (that’s so demeaning) light.

Oh believe me I get it, at the risk of being removed from the forum you don’t talk about politics, religion, or the original oil pressure transmitter vs the idiot (harsh) light. Them there is fightin’ words :sunglasses:

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Yes it arrived from Amazon and I fitted it a few days ago. It did read high, as I expected. I’d planned to fit a resistor to get it to match the cabin gauge so I had a 75Ω I’d made up a few years back and also the 60Ω resistor that’s fitted in conjunction with the switch.
This ÜRO C46272 unit’s 3/4" fitting was quite a bit slimmer than than OEM so the crowfoot was too thick to fit between it and the block so I ended up bending a 3/4" wrench and used that instead.
On the drive home (about 30 mins from the workshop) the gauge showed almost at max and dropped slightly at hot idle. All good, planned to fit resistor next day. Well, plans don’t always work out and about 2 blocks from home the pressure on the gauge dropped down to just above zero. After I parked, I noticed oil stains on the wet road surface which seemed to be coming from my car …so I guessed I hadn’t tightened it down enough and had a small (well not so small) oil leak.
Fast forward to today. Checked oil level and I was down a bit, topped it off and headed back to the workshop. Removed the unit again and added teflon tape to the threads, reassembled and started the car. Leak was now worse, dripping oil every second.
Decided to take it off (AGAIN!) and pressure test it. It wasn’t leaking at the threads, oil was pissing out of the back of the unit where the connector was mounted.
The old sender had been sitting in solvent since I originally changed it the previous week so I decided to refit it and even if it didn’t work properly at least it wouldn’t spew oil all over the place.

Of course after I refitted it, it worked just like new again. Was probably gummed up. Returning defective unit and do not recommend that particular aftermarket replacement, construction/design not adequate.

Hi, I am new to the XJ40 world… not really sure I want to be here at all, but my brother has bought a 1988 Daimler… I read this post area with interest… This car has the oil gauge which starts as ‘normal’, then continues to get higher until it maxes out and stays there. Is this an indication of sender failure, gauge failure or maybe the wrong sender? thanks

When the sender is failing it is *usually * the opposite, ie the readings are normal when the engine is cold then drop down when it is hot. Maybe a PO had that problem and has fitted the wrong sender. The good news is, in the many years I’ve been on this forum so far I haven’t read about an XJ40 suffering from actual low oil pressure, it has always been down to a failing sender, it’s a fairly bulletproof engine when maintained properly.


Morro - refer to post #23 (March 7) in this thread by abercanadian a/k/a Larry Stephen - my guess would be (as would Larry’s, I believe) the wrong type of sender.

Thanks for tsking the time to respond. Cheers