Oil pressure gauge

Oil pressure gauge

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Skyedriver

Original Poster:

17,667 posts

281 months

Thursday 24th April 2014
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Well, apart from being locked out today by errant central locking, I noticed the oil pressure gauge going a bit erratic.
Ignition on it hits 90lb/in, start up it'll sit at 40 when running, suddenly it'll jump to 90, stay there for a while then drop to normal or flicker rapidly between the two positions.
At first I was worried expecting blown seals everywhere then realised it was probably an electric fault.
Any clues as to where to start looking first?
Ta









phazed

21,844 posts

203 months

Thursday 24th April 2014
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First thing is to make sure you have a nice tight electrical connection on the sender unit.

Pull of the spade connector, clean, recrimp, refit and test.

Skyedriver

Original Poster:

17,667 posts

281 months

Friday 25th April 2014
quotequote all
Cheers phazed
Agreed, but last night it was dark by the time I'd walked the dog, fed the bairn, sorted (not) a PC, fed the wife, cut the grass and then blew the tyres up. I knew my old Chimaera had no power steering and was lighter than this one.. tyres at 15lb on the front...
So this weekend I'll be under the bonnet (and possibly the dash).
Oh and going to BAR111...

QBee

20,906 posts

143 months

Friday 25th April 2014
quotequote all
Skyedriver said:
Cheers phazed
Agreed, but last night it was dark by the time I'd walked the dog, fed the bairn, sorted (not) a PC, fed the wife, cut the grass and then blew the tyres up. I knew my old Chimaera had no power steering and was lighter than this one.. tyres at 15lb on the front...
So this weekend I'll be under the bonnet (and possibly the dash).
Oh and going to BAR111...
You may already know this, but.....you need to get under the front of the car, not the bonnet. Jack up the car, axle stands in, wriggle under, the connector is immediately under the crankshaft pulley. Just the one wire, cable tied to the chassis cross member.

I finished a successful track evening at Snetterton about two weeks ago, loaded up the car and got onto the A11, glanced at the gauges - zero oil pressure. yikes Had a Phazed moment (see other threads about zero oil pressure on track days, baffled sumps, baffled drivers etc etc).

Phoned my TVR guy (who was about 800 yards behind me, still talking to friends at the circuit) and asked him to come and have a look. In the dark we couldn't see anything other than the dipstick (the one under the bonnet, not the one behind the wheel), but he suggested this fault having checked i wasn't pouring oil onto the A11. After stopping for a MacRefreshment, I did get some oil pressure back on accelerating, but it disappeared when i braked. Next morning I got underneath the car. The connector was loose, only help on by the stiffness of the wire. Crimped it up, all well again.

If not that fault, perhaps check the terminals on the back of the gauge itself for a loose connection?

Skyedriver

Original Poster:

17,667 posts

281 months

Friday 25th April 2014
quotequote all
Thanks
Might well have caught it when under there last week tightening the starter motor leads...
Tony H

Skyedriver

Original Poster:

17,667 posts

281 months

Sunday 27th April 2014
quotequote all
Crawled underneath this morning, the single lead to the small dender is now cleaned and tight, am I right in thinking the large one above is for the guage?
There is a wire to a post & nut but on the ther side thre is a post with a male spade terminal but no wire and no loose wire any where, is this normal?
Tony H

Chuffmeister

3,597 posts

136 months

Sunday 27th April 2014
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Skyedriver said:
Crawled underneath this morning, the single lead to the small dender is now cleaned and tight, am I right in thinking the large one above is for the guage?
There is a wire to a post & nut but on the ther side thre is a post with a male spade terminal but no wire and no loose wire any where, is this normal?
Tony H
A photograph speaks a thousand words Tony!

Skyedriver

Original Poster:

17,667 posts

281 months

Monday 28th April 2014
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Hard enugh getting me underneath there and able to see!
Next time it's up on ramps I'll see what I can do

Skyedriver

Original Poster:

17,667 posts

281 months

Tuesday 6th May 2014
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This is the current sender, two posts, one with a wire to it, the other with a spade terminal but no wire and none loose anywhere (that I can find).
Would love to know what the other terminal is for, and why the gauge swings to max when I turn on the ignition.


spend

12,581 posts

250 months

Wednesday 7th May 2014
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That's normal on your car (90% of phers are not at all like that, with serp timing cover and welsh gauges).

The 'other' terminal is often a pressure switch (but sometimes they didn't fit the internals). The pressure sensor is connected via a ring terminal and the spade connector is a 'nice' reminder which is the unused connector.

ChimpOnGas

9,637 posts

178 months

Wednesday 7th May 2014
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On a two terminal oil pressure sender the second terminal will either be.....

A: The earth

B: For a warning light

Are you sure it's not the earth type?

Run a fly lead from the second terminal to earth and see what the gauge does, if it's the warning light type you won't do any harm.

If it's the earth type you'll probably fix your errant readings.

spend

12,581 posts

250 months

Wednesday 7th May 2014
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Sounds good, but probably grasping at straws..

AIUI full earth gauge goes to top... no earth gauge reads zero..

So with a gauge reading normally, touching gauge sensor wire to earth would make it flick up to 90, which as I read the OP is what is seeing.

I would deduct either faulty sender/gauge or sense wire touching ground as gauge flickers overscale.

Any grounding problem would result in gauge flicking to zero AFIK.

ChimpOnGas

9,637 posts

178 months

Wednesday 7th May 2014
quotequote all
These bellows type oil pressure senders are notoriously unreliable and typically have quite a short life, common to Jag XJ6's & the like back in the seventies they were rubbish then & are no better now.

I've been using this cheapo EBay one with good results for a few years now:

http://www.ebay.co.uk/itm/370678852601?_trksid=p20...

You need to run an earth lead off the second terminal and make a converter lead to go from spade to ring terminal on the original TVR gauge wire, but these are easy 5 minute jobs.

More recently I found this one:

http://www.ebay.co.uk/itm/150918952129

It's longer and more expensive than my cheapo one, but all reports seem to indicate it's the most accurate sender yet.

You could just buy an original sender from a TVR specialist, but there's no proof it'll be any more accurate or reliable long term and you'll be paying almost twice.

Actually in my experience the original wasn't well matched to the gauge anyway and gave unrealistically low readings, typically around 10 - 15psi (or more) below the true pressure.

I'd fit this one and have done with it.



http://www.ebay.co.uk/itm/150918952129

Skyedriver

Original Poster:

17,667 posts

281 months

Wednesday 7th May 2014
quotequote all
Thanks CoG
I'll have a look at a replacement I think.
ps sorry the photo was a bit blurred.

Often thought about having a chat about your LPG project, but think I've got a few other things to sort first.

ChimpOnGas

9,637 posts

178 months

Wednesday 7th May 2014
quotequote all
Skyedriver said:
Thanks CoG
I'll have a look at a replacement I think.
ps sorry the photo was a bit blurred.

Often thought about having a chat about your LPG project, but think I've got a few other things to sort first.
You're welcome.

FYI, the LPG is proving to be a great success, I'm making 3hp more on gas than petrol & seeing the cost equivalent of 36mpg overall where petrol is 25mpg overall.

The car delivers 250hp & 260 ft/lbs of torque on either fuel which makes it a strong 4 litre so I'm told.

Best economy seen so far is the cost equivalent of over 43mpg.

A fill of LPG is just £41 and takes me almost 300 miles before she needs topping up again, try that on petrol & your wallet will be £75 lighter to cover the same distance.

Flick a switch for a further 160 miles of petrol and you just can't tell the difference between fuels.

Ferrari fast, Fiesta economical... whats not to like?

Skyedriver

Original Poster:

17,667 posts

281 months

Saturday 14th June 2014
quotequote all
ChimpOnGas said:
These bellows type oil pressure senders are notoriously unreliable and typically have quite a short life, common to Jag XJ6's & the like back in the seventies they were rubbish then & are no better now.

I've been using this cheapo EBay one with good results for a few years now:

http://www.ebay.co.uk/itm/370678852601?_trksid=p20...

You need to run an earth lead off the second terminal and make a converter lead to go from spade to ring terminal on the original TVR gauge wire, but these are easy 5 minute jobs.

More recently I found this one:



It's longer and more expensive than my cheapo one, but all reports seem to indicate it's the most accurate sender yet.

You could just buy an original sender from a TVR specialist, but there's no proof it'll be any more accurate or reliable long term and you'll be paying almost twice.

Actually in my experience the original wasn't well matched to the gauge anyway and gave unrealistically low readings, typically around 10 - 15psi (or more) below the true pressure.

I'd fit this one and have done with it.



http://www.ebay.co.uk/itm/150918952129
http://www.ebay.co.uk/itm/150918952129
Left this problem aside for a few weeks due to there non TVR problems but back on the case,
On the early engine, do I need the two terminal one - would the single terminal one earth ok through the body?


ChimpOnGas

9,637 posts

178 months

Sunday 15th June 2014
quotequote all
Skyedriver said:
would the single terminal one earth ok through the body?
Either will work, but personally I prefer the two terminal type as you can PTFE tape the thread for an oil tight seal, something you wouldn't want to do if you're relying on earthing the sender through the block.

Others may disagree but I also feel a separate dedicated earth lead direct from the sender to the chassis offers a more reliable earth than goinig through the block.

But like I say either will work, the biggest problem with these senders is not the earth but their unreliable bellows design, over time hot corrosive engine oil inevitably attacks the diaphragm causing the unit to leak and give erratic readings.

I'm looking at an elecronic pressure sender that will be significantly more accurate, reliable & oil tight, the challenge is however to pair it correctly to the gauge but I have a clever box of electronics that will solve this.

Watch this space wink


Chuffmeister

3,597 posts

136 months

Sunday 15th June 2014
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Blimey, these have had TVR tax added since I last looked. Almost specialist prices.

Skyedriver

Original Poster:

17,667 posts

281 months

Saturday 28th June 2014
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Well I thought this was going all to easily.
Old sender out, it screws into a brass adapter which came out with it.
New sender into old adapter, screws into engine, snaps adapter.................
Any ideas where I can get a new one please, off the shelf at an outoparts place or are they a special?
Thanks

Skyedriver

Original Poster:

17,667 posts

281 months

Saturday 28th June 2014
quotequote all
Bump - any guidance