[komaterpillar]

Just a quickie update.  Took car off incline ... no oil light after initial start up and parked level ground.  checked oil again ... full!  Drove 1/2 mile to work ... no light!!!  Oil check and under car after 4 hrs ... full/nothing on ground.  Took for run up very steep hill, parked then back down hill, parked ... NO OIL WARNING LIGHT!  back to level, checked oil levels again few hrs later... all good.  So have to assume that the slope and low oil was the issue but regardless speaking to garage about selling car without checks they said done and want a full check over to confirm this was the issue.  Let you know outcome.
Nx

Great news 

[eye30]

i unplugged the wire going to the oil pressure sender then turned the ignition on - no light illuminated on the dash, then started the car - still no light illuminated on the dash,

Have you got a problem????

[Doggie 1]

Just a quickie update.  Took car off incline ... no oil light after initial start up and parked level ground.  checked oil again ... full!  Drove 1/2 mile to work ... no light!!!  Oil check and under car after 4 hrs ... full/nothing on ground.  Took for run up very steep hill, parked then back down hill, parked ... NO OIL WARNING LIGHT!  back to level, checked oil levels again few hrs later... all good.  So have to assume that the slope and low oil was the issue but regardless speaking to garage about selling car without checks they said done and want a full check over to confirm this was the issue.  Let you know outcome.
Nx

Great news 

Yes, that is good news. 

[komaterpillar]

i unplugged the wire going to the oil pressure sender then turned the ignition on - no light illuminated on the dash, then started the car - still no light illuminated on the dash,

Have you got a problem????

What do you mean have i got a problem???   Are you having a go at me???

All I am doing is working out what the problem with the OP's car and explaining how and why i have come to the conclusions that i have, trying to eliminate speculation, after all it is only my bloody trade,    if ya don't want my advice or want to hear what i know or have worked out, let me know and I'll refrain from posting...

[eye30]

i unplugged the wire going to the oil pressure sender then turned the ignition on - no light illuminated on the dash, then started the car - still no light illuminated on the dash,

Have you got a problem????

What do you mean have i got a problem???   Are you having a go at me???

All I am doing is working out what the problem with the OP's car and explaining how and why i have come to the conclusions that i have, trying to eliminate speculation, after all it is only my bloody trade,    if ya don't want my advice or want yo hear what i know or have worked out, let me know and I'll refrain from posting...

You say you removed the lead and the light didn't come on. 
From previous postings I understand that it should as there is a break in the line.
Have I misunderstood this?

[komaterpillar]

i unplugged the wire going to the oil pressure sender then turned the ignition on - no light illuminated on the dash, then started the car - still no light illuminated on the dash,

Have you got a problem????

What do you mean have i got a problem???   Are you having a go at me???

All I am doing is working out what the problem with the OP's car and explaining how and why i have come to the conclusions that i have, trying to eliminate speculation, after all it is only my bloody trade,    if ya don't want my advice or want yo hear what i know or have worked out, let me know and I'll refrain from posting...

You say you removed the lead and the light didn't come on. 
From previous postings I understand that it should as there is a break in the line.
Have I misunderstood this?

sorry, thought you were having a go at me!

the ecm sends a voltage down the wire to the sender, if there is no oil pressure the sender switch closes and completes the circuit - illuminating the light, on the other hand if there is oil pressure the sender switch opens and breaks the circuit - making the light go out.

so therefore if you unplug the sender this is effectively breaking the circuit and the light can not illuminate unless the sender wire earths somewhere else (through a short).

this is how a earth switch works 

also if you were to pull the wire off the sender and touch it onto the block somewhere or any earth, this would complete the circuit and illuminate the light.

make sense?

[2i30s]

 

.. make sense?

Yes, although I must say I'm surprised at the negative logic. I would have designed it to fail the other way.

I must also say that I'm surprised that just 0.5 litre low on oil could allow the pump to starve, even on a slope.  I'm thinking that the dipstick reading was misinterpreted perhaps?

[eye30]

make sense?

Yes it does now.  Thank you.

sorry, thought you were having a go at me!

No, not at all,   Sorry.  Reading my post again I should have also added at the end -- "with your car".

[komaterpillar]

I must also say that I'm surprised that just 0.5 litre low on oil could allow the pump to starve, even on a slope.  I'm thinking that the dipstick reading was misinterpreted perhaps?

possibly,

my thinking was that maybe a combination of factors may have been at play,
for instance, my post about oil quality - maybe the vehicle is overdue or about due for a service thus the oil quality has deteriorated (maybe thickened up/sludgey?),
the problem occured after being parked thus you could presume cold engine and oil = thicker oil that will not drain back through return galleries quick enough to the sump,
being parked on a mad slope, wich will mean that the oil is more likely to pool in the top end of the engine thus not returning to the sump quick enough,
being parked on the mad slope, would have made the oil pool on one side of the sump, and depending on where the pickup is it may not be fully imersed in oil.

add all these factors up and depending on where the pickup is on the bottom of the sump, i reckon it could result in the pickup being partially exposed and able to suck air, not entirely losing oil pressure but dropping it off enough at idle to make the light flicker. thus when the engine was reved the pickup would suck enough air/oil to develop enough pressure to open the oil pressure switch turning the light out. and then when the engine is returned to idle, all the oil is still pooled in the top end so the oil pressure would drop back off illuminating the light.

[Phil №❶]

just had a look at our 2.0 litre petrol, i unplugged the wire going to the oil pressure sender then turned the ignition on - no light illuminated on the dash, then started the car - still no light illuminated on the dash, there is only one wire going to the sender this tells me that the pressure sender is an earth switch,,,,, or your oil light bulb is blown 

Seriously, this is a good demonstration of the different logic involved in car wiring harnesses.

Relays, transistors. diodes and Zener diodes all can be configured to work when power is applied or to work when power is absent. Poking around with a test lamp doesn't prove a thing unless you know what sort of logic is being employed in the wiring. 

[komaterpillar]

sometime over the next couple of days i'll try and put a proper calibrated test gauge in a oil pressure port to see at what pressure the light actually does go out and come on at, for future reference.

it would also be good to record the oil pressure at idle and 1500rpm as this can be a good indicator of the condition of your oil pump, pressure relief valve, main and bigend bearings,

will let ya's know what the readings are if you want? might be good for comparison?

[Phil №❶]

That's great, can never have too much information. 

[komaterpillar]

just had a look at our 2.0 litre petrol, i unplugged the wire going to the oil pressure sender then turned the ignition on - no light illuminated on the dash, then started the car - still no light illuminated on the dash, there is only one wire going to the sender this tells me that the pressure sender is an earth switch,,,,, or your oil light bulb is blown 

Seriously, this is a good demonstration of the different logic involved in car wiring harnesses.

Relays, transistors. diodes and Zener diodes all can be configured to work when power is applied or to work when power is absent. Poking around with a test lamp doesn't prove a thing unless you know what sort of logic is being employed in the wiring. 

first up the bulb is not blown

secondly i just did a continuity test on the oil pressure sender, continuity through the switch with the engine off (no oil pressure), no continuity through the switch with engine running (oil pressure)

Just thinking about it a bit more, normally closed continuity at no pressure allows the indicator lamp to light before starting the engine. If nothing else this shows the lamp is working. I'm assuming here of course there is no extra logic involved and really, there should not be any need to complicate something so simple.

WRT the oil level needed to ensure pressure: I did coincidentally have occasion to look at my son's car last week after he noticed the oil light flickering. It was due a change anyway but I was surprised it could have had oil low enough to give low pressure (this should never be allowed to happen!). It did. Not even a smidge on the dipstick. It turned out the oil filter had loosened and the oil leaked out. Damn that bugger that did the last service. 

I drained (sucked) the oil and there was about 1 litre, if that. The pickup must (of course  ) be at the very bottom. Hence my scepticism here that the OP oil was low enough to cause low pressure.

[komaterpillar]

Just thinking about it a bit more, normally closed continuity at no pressure allows the indicator lamp to light before starting the engine. If nothing else this shows the lamp is working. I'm assuming here of course there is no extra logic involved and really, there should not be any need to complicate something so simple.

EXACTLY RIGHT

[Nx]

 

I spoke to soon!  Popped out to shops ... no prob, parked car in drive (decline) and the (F@x7) light came on again (permanant not flashing!)... but have already informed garage of issue and they 1st very upset that the oil was low in the first place!  2nd would like the car back asap to do full checks and offered courtsey car for day!  As Ad-hoc think sensor is issue, though not checked oil level since last night ((   Hey ho ... thought for day -  I have made so many friends who have the same car as me!  Smiling still regardless 

Thank you all for advice, support and friendship
Nx

DUH ... add a kiss on the emotions pls! XXX

[Dazzler]

  (I'll see wat I can find) 

Test

[Nx]

Luv them but how do I get them or display them!!!  Now def being Dum 

[Dazzler]

Luv them but how do I get them or display them!!!  Now def being Dum 

Not a dumb question I'll upload a couple to the database when I get a chance

I've uploaded these three 

[Shambles]

Dazz you big softy

[Phil №❶]

Luv them but how do I get them or display them!!!  Now def being Dum 

Who are they for Nx 

[Dazzler]

Luv them but how do I get them or display them!!!  Now def being Dum 

Who are they for Nx 

For everyone where appropriate of course

[Nx]

 

To all of you out there!  Car in garage Thursday for full check over.  Will let you know the results.  Thanks again for being so helpful and friendly 

Nx

[Dazzler]

No worries (I think there is a "light" at the end of the tunnel  )

[Nx]

 
Well my lovelies ... not too bad a day!  Took car to garage and bless she did me proud by ensuring the warning light on when I got to garage!  Bless I got 5* treatment - though courtesy car a bit ruff and took some work in getting used to LOL  I have my car back for the night, waiting for part (in tomorrow).  It was the sensor malfunctioning and was causing an extremely minor leak which over time I would have noticed but since only done 60 miles since I bought her, not surprised didn't notice it!  They have assured me my car OK to drive till part replaced.

OK so once replaced will still check oil every other day for a month to double check!!! I had a bit of moan about handbrake (which was a bit high) and a blown bulb when arrived, all sorted when collected and no charges!  I know that under warranty but they could have charged me for the bulb LOL

So hopefully this time tomorrow I will have a fully happy car and she will have a fully happy owner!  I have a few long trips coming up in the next 2 months (Surrey to Derbyshire and Coventry!) , so will be able to test all working correctly. 

So again am very grateful to all for advice and support.  Just think if I didn't have a prob I wouldn't have found this wonderful site and lovely people for a while! 

Now need to look more into this site and see if you have a general chit chat forum, or online chat facility ... don't want to lose touch with you all.

 
Nx

[Dazzler]

Fantastic  .. We chat about anything and everything in various treads (so have a good look around and make yourself at home) 

[Nx]

Dazzler ... ur just a car tart! LOL   X

[Dazzler]

Dazzler ... ur just a car tart! LOL   X

Jeepers, you already worked that out (don't tell my Wife who is also a member - TrishCW) 

[eye30]

Great result and it is especially better as the light was on when you got to the garage so they could see the issue.