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Author: Subject: 919 Blade - Oil pressure with engine off?
paul1087

posted on 17/6/18 at 09:14 AM Reply With Quote
919 Blade - Oil pressure with engine off?

Morning chaps.

Did an oil and filter change yesterday on my 919 blade following a track day last week.

Nothing nasty in the oil so that's all good.

I am wondering if my pressure sensor is on its way out though - Its reading between 5-7psi with the engine off?
Then on start up at idle its approx 70-80 psi.

A quick run up through the gears is showing up to 105 psi.

On the track day the oil pressure didn't go past 80 something.




The other thing I noticed - after topping up 3.7 litres of the fresh stuff, starting engine to fill filter and let it run for a few mins - cant see a thing in the sight glass?

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snapper

posted on 17/6/18 at 12:03 PM Reply With Quote
1 or 2 wire sensor?
What connections does the gauge have?
Gauge should display max if sensors disconnected
Should show zero if power to gauge disconnected





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ReMan

posted on 17/6/18 at 06:26 PM Reply With Quote
What gauges?





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paul1087

posted on 17/6/18 at 06:27 PM Reply With Quote
It's a digidash
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ReMan

posted on 18/6/18 at 08:36 PM Reply With Quote
quote:
Originally posted by paul1087
It's a digidash

I was thinking whether it is calibrated to the clocks correctly?





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gingerprince

posted on 19/6/18 at 06:29 AM Reply With Quote
Most likely a poor earth connection. The digidash measures resistance across the sensor - any resistance in the earth connection will show as PSI on the dash. Mine did exactly the same, but was good after I rewired the car over winter.

Test resistance between G terminal and casing, then again between G terminal and battery -ve. If there's a noticeable difference that's your problem. If not it's possible the sensor itself has gone awry, but rule gnd out first

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Jon Ison

posted on 19/6/18 at 03:11 PM Reply With Quote
How's the sensor mounted?

If it's screwed into engine they don't last long due too vibration, need to be remote on a little flexible pipe even then they go over time with vibrations.

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paul1087

posted on 21/6/18 at 06:11 PM Reply With Quote
Hi chaps,

Went to take a look at the sensor earlier, I've taken some pictures in the hope someone can point me in the right direction for where to point my multimeter!

My sight glass is still showing no oil too... Any comments?

Lastly - it appears I've got quite an oil leak.. ....


















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gingerprince

posted on 21/6/18 at 08:20 PM Reply With Quote
What's with the wrapping/cable ties around the bottom pressure switch/tee-piece?

Looks like you've got 2 sensors - the one at the bottom is just a pressure switch (for warning light only). This is wired to a tee-piece which is then remote mounted to your combination switch/sender for the ETB. There should be no reason to have both the bottom switch and the top sender - the top one has 2 connections - "G" which is for gauge, and is a variable resistance depending on pressure. The other is marked "WK" which is wired up to your low-oil warning, and duplicates what the original oil pressure switch does. Why you have 2 connected I don't know, and without knowing where each wire goes in your loom it's hard to be sure, though I'd guess that you've got one warning light wired to the Digidash, and the one from the oil pressure switch to another, separate oil pressure light on the dash or something?

But looking at your pressure sender, it doesn't look like it's got an earth. It should earth via the body - if plugged into the engine directly (which is a bad idea due to vibration) then it earths itself, but remotely mounted as you have, you should have a good earth connection clamped to the body - I have a fly-cable, with a spade connector sandwiched between the body and the mounting jubilee clip, which then mounts to chassis. In yours it looks like the remote mount/braided hose is your earth, which will be a poor connection and the likely reason for your misreading.

As for the oil level - if you can't see oil in the window, you need to put some more in!!!

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paul1087

posted on 21/6/18 at 09:18 PM Reply With Quote
Thanks for your help.

I believe the bottom sensor is a temperature sensor. Its td off before the remotely mounted pressure sensor.

Its wrapped to prevent it being cooled by wind and reading low.

Thanks for the pointers re: the earth on the pressure sensor. I will get this sorted on the weekend, would any form of connection be suitable for this? Or would you recommend a specific cable gauge? Apologies if a stupid question, this is all new to me!

Lastly, the sight glass... I just topped up 3.6 litres of fresh oil, I wouldve expected this to at least register on the window?
Should I just keep filling it up until visible and brimmed right to the top line?

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gingerprince

posted on 22/6/18 at 01:41 PM Reply With Quote
quote:
Originally posted by paul1087
Thanks for your help.

I believe the bottom sensor is a temperature sensor. Its td off before the remotely mounted pressure sensor.



OK that makes sense.

quote:
Originally posted by paul1087
Its wrapped to prevent it being cooled by wind and reading low.



Not sure a tape "jacket" will make a difference - the temperature sender is on the inside in contact with the oil. Wouldn't expect wind to make a difference unless its actually cooling the oil inside...

quote:
Originally posted by paul1087
Thanks for the pointers re: the earth on the pressure sensor. I will get this sorted on the weekend, would any form of connection be suitable for this? Or would you recommend a specific cable gauge? Apologies if a stupid question, this is all new to me!



It's not carrying any current, so wire gauge shouldn't matter - just a good solid crimp/solder - make sure the body of the sender is clean where you clamp it, and ideally test that resistance between the body and your earth point is negligible once you've tightened it up.

quote:
Originally posted by paul1087
Lastly, the sight glass... I just topped up 3.6 litres of fresh oil, I wouldve expected this to at least register on the window?
Should I just keep filling it up until visible and brimmed right to the top line?



Make sure you're level - fill it until you can see it (so it's safe to warm up), then run it until warm and top up to upper line.

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paul1087

posted on 22/6/18 at 08:39 PM Reply With Quote
Update...

Sorted a good earth earlier.
Then tested the sensor as per instructions above.

Sensor is fine as resistance was about the same between the terminal and body as the terminal and battery negative.

When warm the oil pressure is approx 40psi at idle.

But rapidly climbs up to 110 max when driving up through the gears..

What's next to check... Pressure release valve?

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