Oil pressure gauge drop off.

[BigBlueCat]

Anyone give me a clue, my oil pressure gauge keeps dropping to zero, I was advised it may be an oil pressure sender malfunction, so changed that out for a new one, Jag main dealer supplied. The new one seems to have made it worse, with the old sender in place the guage only zero'd on odd occasions, now with the new one, I get a reading until the engine is hot, pressure well up on the guage. Once the engine is hot, the guage drops to zero and won't register again until she's stood over night, although on odd occassions the guage will spring to life mid drive and work fine. I've had no oil warning lights, no oil leaks and don't seem to be useing any oil.
I may refit the old one to see what happens.
Any thoughts.

[davidr]

Hi Dave - sounds like an electrical connection fault to me. Dirty or corroded connection somewhere?

[poprivet]

The printed circuit board on the back of the instruments is a likely area of bad connections. Fairly easy to take apart and clean and a good opportunity to replace the dim bulbs with LEDs

[davidr]

Dave - reading your post again I would also check the wiring from the sender to the instrument pack for continuity. It could be that the wiring is corroded or broken and that as it heats up the resistance in the marginal connection increases and the signal is lost? There will be better electrical engineers than me on here (not hard!) who I'm sure will advise!
One advantage you do have is that the oil pressure sender and the sensor for the low pressure light are entirely separate systems. If they both indicate no pressure then you need to take that seriously!

[BigBlueCat]

Davidr, thanks for that, I have spotted a multi connector in line from the pressure sender and the bulkhead that the sender wire goes into, may look at that. I have a good motor electric engineer buddy who can test it for me, not brilliant with auto electrics either. I'll keep you posted.

[BigBlueCat]

The printed circuit board on the back of the instruments is a likely area of bad connections. Fairly easy to take apart and clean and a good opportunity to replace the dim bulbs with LEDs

Cheers poprivet, I've got a buddy to test things for me, I'm not the worlds best auto lec I have to admit, LED's already done through out the car, nice green glow to the dash.

[ptjs1]

Dave,

did you test the original sender first or just change it? If I were you, I would run a resistance test of the new sender (and also replace the original sender and do the same test on that). I suspect you'll find that both senders are operating appropriately and the problem lies further downstream in the wiring integrity or the cluster integrity. It's always recommended to do this type of diagnostic test before changing any part.

Good luck

Paul

[poprivet]

I might be thinking of a different model but wasn't there a discussion some time ago about new senders just giving a 'normal' reading if there was any pressure rather then a scale reading? i.e. a switch

[ptjs1]

Pop,

that was certainly true of the facelift 4 litre cars. We're guessing that Dave has a standard 5.3 V12 version. I THINK that the same sensor part number was used on the V12s.

I'd always recommending keeping the original type if it's working ok as it shows a more realistic pressure. Jaguar just changed the part but kept the old part number so finding the old "real pressure" type is quite difficult.

Paul

[davidr]

At risk of getting away slightly from Dave's original post, later oil pressure gauges like my Celebration are the "comfort" type that show a nice steady reading. No use to Man nor beast but does stop nervous owners worrying that their oil pressure drops at tickover (which it should!). Mine has a link lead with some electrical gubbins in it to give that steady reading.

[BigBlueCat]

Paul, no I didn't test the original, but I am planning to refit the original over the weekend and do just as you suggest, I think seeing as the gauge is doing the same with both senders, the fault is probably down stream.

[BigBlueCat]

Pop,

that was certainly true of the facelift 4 litre cars. We're guessing that Dave has a standard 5.3 V12 version. I THINK that the same sensor part number was used on the V12s.

I'd always recommending keeping the original type if it's working ok as it shows a more realistic pressure. Jaguar just changed the part but kept the old part number so finding the old "real pressure" type is quite difficult.

Paul

I Found that quite strange Paul, there are two sensors recommended by Jag, they sent a wrong one first, recommended upgrade part for a V12 only, that one was £17.00, that same part was not a recommended upgrade part for the XJS though, the one identical to mine as already fitted was the second one they sent, surprise, surprise that one rocked in at £40:00.

[BigBlueCat]

At risk of getting away slightly from Dave's original post, later oil pressure gauges like my Celebration are the "comfort" type that show a nice steady reading. No use to Man nor beast but does stop nervous owners worrying that their oil pressure drops at tickover (which it should!). Mine has a link lead with some electrical gubbins in it to give that steady reading.

I've got to say, when the gauge is working, it moves beautifully up and down the scale, drops on tick over and rises gently into the lbs/ft mark and sits rock solid when running. I like yourself prefer it that way

[ptjs1]

Dave,

At the risk of distracting you from your core problem, I'm intrigued by Jaguar recommending 2 different parts. In theory, there is only part number for that sender. Could you let us know the part numbers that they have been sending to you?

Once you get to the bottom of the problem, I'd really suggest you replace your original sender (assuming it's not part of the problem). AFAIK, the new ones look identical but are not of the variable pressure reading as per your original. Keep the original and watch it go up and down as it's supposed to do!

Cheers

Paul

[paulypilot800]

Hi,

I'm a new member here, just bought K82 UAG - a restored (by KWE Jaguar) 1992 XJS 4.0 convertible.
Beautiful car, and the KWE rebuilt suspension, brakes & steering, mean that it goes exactly where it's pointed, reminds me of a 3-series BMW in that regard, almost go-kart like, which is astonishing given that it's a 27 year old land yacht (as my neighbour jokingly described it!)

One thing is giving me anxiety about driving it though - the oil pressure gauge. At the start of a journey, it sits at a nice healthy level of about 6 (where 4 is at 12 o'clock. and 8 is the maximum marking). Then once engine has warmed up, after about say 10 miles, the oil pressure begins falling, down to about 4. Then it goes lower still, as the car slows down, resting just above the red line. I realise that oil pressure will drop as the engine goes down to tickover, but am getting alarmed about it going right down to the red zone.

I stopped at a service station, and let the engine cool down for about half an hour. Then I put in an extra litre of oil. Restarted it, and the oil pressure problem seemed to have been fixed. So I put it down to not having enough oil in the car.
Anyway, I put another litre of oil in the car today, just to be on the safe side, and it seemed to run better, more smoothly, and everything was fine until the same thing happened again - after about 10 miles, the oil pressure started falling, and seems to continue falling,

This is giving me range anxiety, and I'm reluctant to take the car more than a few miles from home.

Can anyone help by telling me what the oil pressure gauge should be doing. I cannot see any oil leaks on the garage floor, and the car had a recent full service before I bought it from KWE. In all other respects the car runs beautifully, and the engine feels & sounds great - no funny noises, and seems to develop plenty of torque, and power.

I'd be grateful for any advice.

Thanks in advance!

Paul.