Sudden low oil pressure ...... sensor fault?

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mittens
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Sudden low oil pressure ...... sensor fault?

Post by mittens » Wed Nov 19, 2014 10:02 am

Hello all,

I've just picked up a '91 8v Gti. The car is awesome and been really well looked after.

I drove it home Sunday covering a good 100 miles and the car ran faultlessly. Oil pressure gauge on 6.
Again Monday I put more miles on it, also oil pressure fine at 6. Now yesterday in the morning it was fine. Then I had a new water hose put on(from right side of engine to back of engine) to replace a repaired hose and then I committed a cardinal sin and put the car through a jet wash :roll:

I noticed driving home that the oil pressure needle was sat on the red. Not enough to trigger any warning lights, but still in the red and not good to see. The car still seemed to drive fine. Have tried starting the car a few times and the needle still just sits in the red.

Would I be right in thinking that hopefully jet washing the car has maybe knocked the sensor out? Or should I be concerned that I could have low oil pressure? I didn't notice the needle drop from 6 to red.

I've ordered a Haynes manual but it hasn't arrived yet. Which sensor is for oil pressure? I notice there's a couple at the front on the engine.
Is it wise to still drive the car or not? My nearest Citroen specialist is about a 35 minute drive away.


Any help / thoughts greatly appreciated.



Geoff

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David
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Re: Sudden low oil pressure ...... sensor fault?

Post by David » Wed Nov 19, 2014 10:38 am

First thing I have to say is: [-X

The oil pressure clock is connected to the bigger sensor on the front of the engine, Its next to the oil pressure switch, (they are easy to tell apart as the switch is smaller) on the right of the engine, at the bottom. I would assume its a wire come off & not an internal fault. Just get underneath & have a look.

Hope that helps.
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Re: Sudden low oil pressure ...... sensor fault?

Post by RobC » Wed Nov 19, 2014 11:00 am

Oil pressure senders for the gauge are notoriously temperamental - you're lucky yours worked at all! Mine goes up by 2 bars when I have the heated rear screen on...

As David says, you still have a separate switch for the oil pressure light as a fail safe. As long as your dash isn't lighting up like a Christmas tree you'll be fine. But naturally 'tis always wise to double check with the dipstick.
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mittens
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Re: Sudden low oil pressure ...... sensor fault?

Post by mittens » Wed Nov 19, 2014 11:06 am

David wrote:First thing I have to say is: [-X

The oil pressure clock is connected to the bigger sensor on the front of the engine, Its next to the oil pressure switch, (they are easy to tell apart as the switch is smaller) on the right of the engine, at the bottom. I would assume its a wire come off & not an internal fault. Just get underneath & have a look.

Hope that helps.

I know, but the girl that works there is hot!!! Dropped the suspension to full low to get a better view 8)

I will go and have a look .... thank you.

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Re: Sudden low oil pressure ...... sensor fault?

Post by mittens » Wed Nov 19, 2014 11:07 am

RobC wrote:Oil pressure senders for the gauge are notoriously temperamental - you're lucky yours worked at all! Mine goes up by 2 bars when I have the heated rear screen on...

As David says, you still have a separate switch for the oil pressure light as a fail safe. As long as your dash isn't lighting up like a Christmas tree you'll be fine. But naturally 'tis always wise to double check with the dipstick.
I see. So if there is a problem I would get a warning light? So still ok to drive?

Oil level is spot on.

No more jetwash :(

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Re: Sudden low oil pressure ...... sensor fault?

Post by RobC » Wed Nov 19, 2014 11:21 am

Yes - when you switch on the ignition (engine not running) you should see the following red lights on the dash, which are all wired into the oil pressure light:

oil pressure (top left)
STOP (centre)
battery (centre)
(i) - for hydraulic pressure (centre)
water level (centre)
(P) (centre - but only if your handbrake is on!) NB this is not wired to the oil pressure light but would usually come on because you'd have the handbrake on when you start the car.

If these all come on when you turn on the ignition then all is working fine.
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Re: Sudden low oil pressure ...... sensor fault?

Post by RobC » Wed Nov 19, 2014 11:29 am

actually thinking about it I think the (i) light isn't on the centre line, but near there!
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Re: Sudden low oil pressure ...... sensor fault?

Post by BXImage » Wed Nov 19, 2014 7:13 pm

Problem with oil pressure scale could come from sensor on the engine block (bad connection, a wire that fell off...) or the dash itself. Inside the dash there is a chip that gets a bit moody after years - it's job is to switch between oil level and oil pressure scale ~15 seconds after you turn on the ignition. It often happens this chip doesn't switch from oil level to oil pressure scale at all, or it switches only occasionaly. It also might happen that oil pressure suddenly drops from 6 bar to 2 bar while driving, and after a second it comes back to normal. Unfortunatelly, this chip can't be bought.

So mittens, just check the dipstick and keep driving. If there is just a problem with loose wire on the sensor, you could easily fix it yourself, but Haznes won't be of much help. Try here instead - http://citroen.tramontana.co.hu/cooling ... ture-gauge, may help you to indentify all the sensors.

And here is the picture of the oil pressure sensor - FAE number is 14500:

Image

Suprisingly it was used in bunch of cars, and can still be found.

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Re: Sudden low oil pressure ...... sensor fault?

Post by Way2go » Wed Nov 19, 2014 7:39 pm

BXImage,,Interesting observation about the chip but it is unusual for a semiconductor/chip to become intermittent rather than fail completely. Are you sure this fault is not attributable to a dry or fractured joint in the viscinity of the meter electronics?

Also, do you have a type number for the chip to check? Although if it is a custom asic for Citroen, I agree there will be no chance.
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Re: Sudden low oil pressure ...... sensor fault?

Post by BXImage » Wed Nov 19, 2014 7:43 pm

My freind was making one useable GTi dash out of 3, I'll check the chip number with him. Unfortunatelly, I'm pretty sure he said this chip was made only for Citroen. :(

Joint still can be the problem, after all these years they need a bit attention for sure. :)

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Re: Sudden low oil pressure ...... sensor fault?

Post by BXImage » Wed Nov 19, 2014 8:08 pm

Here is direct info from my friend - electronic geek. :)
Chip code is TL527N, and another thing that can make the problem is electrolytic condenser 330uF. These things make a problem only in case when there is a problem in switching between scales.

And some pictures:

http://www.forum-auto.com/pole-techniqu ... 795-70.htm

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Re: Sudden low oil pressure ...... sensor fault?

Post by electrokid » Thu Nov 20, 2014 10:36 am

Hi Geoff and welcome to BXClub :-)

Let us know where you live and we may be able to suggest a Citroën specialist who is nearer to you.

Doing a websearch for that IC throws up nothing much except the numpty sites that want you to download toolbars and other crap. The type number, however, is in a standard form for ICs from Texas so it's very unlikely to be a special for Citroën but maybe a special for the automotive industry because it appears to have also been used on the Renault Espace...

http://www.espace-freunde.de/forenarchi ... es/217.htm

I normally already have, or can easily find, data on particular ICs - but not this one, so possibly an 'industry special' made by Texas for a relatively short time.

ICs normally soldier on for ages and usually only fail due to regular electrical stress, static damage, or moisture creeping up through micro-cavities between the 'legs' and the potting compound. I'll keep on looking for the datasheet - it's not going to be a complicated animal and is very likely to be replaceable with something more standard in the unlikely event that it's the chip that has failed - the whole circuit is a timer + a switch - not rocket science.

It is though, more likely to be a dodgy connection rather than the IC or any of the other components - as far as I can see Citroën have been pretty good at applying conformal coating - a sort of thin varnish which protects electronic kit from dampness, so I'd look for connection problems first.

To reiterate what others have said - there are 2 completely separate sensors for oil pressure - one for the gauge and one for the warning light: providing that the warning light comes on with ignition (to show that the bulb is working) and goes off while the engine is running then you have oil pressure. The same applies to the fuel gauge / warning light - the gauge sensor and the low fuel sensor are separate.
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Re: Sudden low oil pressure ...... sensor fault?

Post by electrokid » Thu Nov 20, 2014 10:49 am

1992 BX19 TGD estate 228K Rusty - SORNed
2002 C5 HDi SX estate

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Re: Sudden low oil pressure ...... sensor fault?

Post by electrokid » Thu Nov 20, 2014 11:05 am

1992 BX19 TGD estate 228K Rusty - SORNed
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Re: Sudden low oil pressure ...... sensor fault?

Post by mittens » Thu Nov 20, 2014 7:08 pm

Thank you for all your replies.

After a bit of wire waggling the oil pressure gauge is now working again. I get all the warning lights come on with ignition and they all go out out once engine is started.

Panic over ..... for now :D