oil pressure off the scale - ideas?

[OllyHill]

I've got a 4.0 HC Chimaera that has never shown any oil pressure problems, but on a drive today the oil pressure suddenly rose and remained off the scale - all other indications normal.

I got the car up on a ramp and had a look at the oil sensor by the sump. The connecting wire is in a poor state. After cleaning the wire and restarting, the pressure still remained off the scale. I replaced the spade on the wire and had a mate wiggle the connection to the sensor as I turned the engine on. Although the pressure still over read, as he moved the connection the pressure dropped to normal several times, but would always then shoot back up off the scale. The wire is in a poor condition, so do I just need a new wire from the sensor, or does anyone have any other ideas?

Thanks for your help in advance!

Olly

[jojackson4]

Start with the wire then clean the coneckshion still off the gauge sender foobard

[SILICONEKID343HP]

OllyHill said:

I've got a 4.0 HC Chimaera that has never shown any oil pressure problems, but on a drive today the oil pressure suddenly rose and remained off the scale - all other indications normal.

I got the car up on a ramp and had a look at the oil sensor by the sump. The connecting wire is in a poor state. After cleaning the wire and restarting, the pressure still remained off the scale. I replaced the spade on the wire and had a mate wiggle the connection to the sensor as I turned the engine on. Although the pressure still over read, as he moved the connection the pressure dropped to normal several times, but would always then shoot back up off the scale. The wire is in a poor condition, so do I just need a new wire from the sensor, or does anyone have any other ideas?

Thanks for your help in advance!

Olly

Just purchased one of these ,Dave Chimongas thinks they are better than the OE one and give more realistic readings .will post the results when fitted tomorrow.

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

[OllyHill]

Thanks for the link - but I'm not sure if it's the sensor itself that's the problem or the connecting wire - wouldn't the fact the reading on the pressure scale changed as the wire was jiggled suggest the wire might be the problem? I haven't had the car long so like I say any advice is more than welcomed!

[chris1972]

SILICONEKID343HP said:

Just purchased one of these ,Dave Chimongas thinks they are better than the OE one and give more realistic readings .will post the results when fitted tomorrow.

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

I though you had one of those already Daz? Does it matter which way around the resistance is marked? Have just seen this, but as opposed to 33 - 240 Ohms, it is 240 - 33 Ohms.

[ur]http://www.ebay.co.uk/itm/Stewart-Warner-Oil-pressure-sender-0-100-psi-240-33-ohms-output-grounded-/251203161110?pt=Motors_Car_Truck_Parts_Accessories&hash=item3a7ce00c16[/url]

Edited by chris1972 on Tuesday 6th August 22:02

[SILICONEKID343HP]

chris1972 said:

I though you had one of those already Daz? Does it matter which way around the resistance is marked? Have just seen this, but as opposed to 33 - 240 Ohms, it is 240 - 33 Ohms.

[urlhttp://www.ebay.co.uk/itm/Stewart-Warner-Oil-pressure-sender-0-100-psi-240-33-ohms-output-grounded-/251203161110?pt=Motors_Car_Truck_Parts_Accessories&hash=item3a7ce00c16[/url]

No purchased another one at the same ohms range, it sits at 80 psi on idle ..does anyone want it for free ? I have a Land Rover one which reads exactly same as the OE one but needs a 1/2"npt to 1/8th npt adapter which cost £3.

[chris1972]

SILICONEKID343HP said:

No purchased another one at the same ohms range, it sits at 80 psi on idle ..does anyone want it for free ? I have a Land Rover one which reads exactly same as the OE one but needs a 1/2"npt to 1/8th npt adapter which cost £3.

I gather that this will potentially mean more leaks with the extra adapter?

[chris1972]

OllyHill said:

I've got a 4.0 HC Chimaera that has never shown any oil pressure problems, but on a drive today the oil pressure suddenly rose and remained off the scale - all other indications normal.

I got the car up on a ramp and had a look at the oil sensor by the sump. The connecting wire is in a poor state. After cleaning the wire and restarting, the pressure still remained off the scale. I replaced the spade on the wire and had a mate wiggle the connection to the sensor as I turned the engine on. Although the pressure still over read, as he moved the connection the pressure dropped to normal several times, but would always then shoot back up off the scale. The wire is in a poor condition, so do I just need a new wire from the sensor, or does anyone have any other ideas?

Thanks for your help in advance!

Olly

Olly, turn your lights on etc and see what the needle does. It may be an earthing issue.

[OllyHill]

How do you mean turn the lights on? Do you mean turn the key the first couple of clicks, get the pump and warning lights illuminated? As soon as I do that the needle shoots off the scale - so would that point to the earthing issue?
If I can get it up on the ramps tomorrow and electrically tested is there a correct voltage it should be putting out?
Cheers for the help

[chris1972]

I have an earthing issue myself and need to get the dash off. It is just one of the things to check. However, the original senders were earthed through the block.

The only reason I mentioned this is because my needles are affected by the lights (slight increase). The original TVR oil sender has an inbuilt dampener, so the needle shouldn't shoot off the scale. You may find that it is the sender itself as my old oil sender used to shoot to zero on hard acceleration. The sender is the likely culprit.

[OllyHill]

Cheers - I will try it with the lights tomorrow, but can't see how the needle can be moved any further as it's already about as far off the dial as it can be.
Really hoping this isn't going to be a huge fix - don't like the idea of having to take the dash apart...

[chris1972]

OllyHill said:

Cheers - I will try it with the lights tomorrow, but can't see how the needle can be moved any further as it's already about as far off the dial as it can be.
Really hoping this isn't going to be a huge fix - don't like the idea of having to take the dash apart...

Follow the link Daz gave you and change the sender first. It is the likely culprit.

[Sardonicus]

The damper is in the sender not the gauge Chris

[chris1972]

Sardonicus said:

The damper is in the sender not the gauge Chris

[jamienshelly]

If you bridge the sender wire to a good earth the gauge should rise to the max position, then wiggle the wire and if it drops to zero at any point if it does then there is a fault in the wiring, but as has been said it sounds like the sender and it cant do any harm knowing that the sender is ok.

[SILICONEKID343HP]

Just fitted the ebay sender ,I`m getting readings of 60psi .I fitted a simple wire from the sender to the chassis ground ,only took me 10 minutes ..Fingers crossed it should be fine ..

[chris1972]

SILICONEKID343HP said:

Just fitted the ebay sender ,I`m getting readings of 60psi .I fitted a simple wire from the sender to the chassis ground ,only took me 10 minutes ..Fingers crossed it should be fine ..

What are you getting on idle when hot?

[SILICONEKID343HP]

chris1972 said:

What are you getting on idle when hot?

slightly less ..Chimongas tested this sender next to some expensive piece of equipment it it followed the real pressure nicely .

Don`t ask me how he did it .

[Sardonicus]

You wont be idling at slightly less than 60 psi HOT no matter who built the engine Daz on a fairly recent build like yours I reckon about 25/30 idle and around 55 or over at + 2.5K RPM stinking hot

Edited by Sardonicus on Wednesday 7th August 14:51

[SILICONEKID343HP]

Sardonicus said:

You wont be idling at slightly less than 60 psi HOT no matter who built the engine Daz

Cold ! will check now on idle ,it`s warm .

http://www.pistonheads.com/gassing/topic.asp?t=984...
chimongas

UPDATE>

Fitted the cheapo Ebay sender today and guess what?

It works perfectly biggrin

In fact I have never seen the needle rise so quickly and give such a solid & consistent reading.

The best I ever saw on the gauge with the old sender was about 38 lbs, and it often fell to 20 lbs when the oil got really hot.

The new sender shows a rock solid 65 lbs.

What killed my tired old sender was the double oil pressure relief spring mod by V8 Developments, I'm sure it was on it's last legs & the extra oil pressure just pushed it over the edge.

The second terminal on the new sender proved to be an earth, a simple fly lead from the earth point on the chassis diagonal to this terminal was all it needed.

I actually prefer a separate earth rather than relying on the unit to earth through the body of the sender as the original does.

Oh, & you do need to change the terminal on the existing live wire from the standard female spade to a ring terminal.

I just made a little 2" converter lead with a male spade at one end and a ring terminal at the other, this way I didn't have to cut the original female spade off.

If I ever need to go back to a TVR sender with it's male spade its just a case of removing my little converter lead.

So if your oil pressure sender is dead or on the way out, you don't need to pay the £50.00 - £60.00 for one advertised specifically for TVR.

Pay £16.00 for this one:

http://cgi.ebay.co.uk/OIL-PRESSURE-Sender-Sensor-f...

Edited by SILICONEKID343HP on Wednesday 7th August 14:55