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Oil pressure gauge not working

Started by _LHSL308_ , Aug 18 2013 09:25 PM

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52 replies to this topic

#1 _LHSL308_

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Posted 18 August 2013 - 09:25 PM

Hi guys and thanks ahead for any advice you can give.

I have the standard oil pressure gauge on the SLR dash. When the dash was installed by my electrician some 2 years ago the oil pressure gauge was working for about 6 months then it just stopped working. As you are all aware the car and engine went in for a rebuild and I got it back a few months ago and the gauge is still not working.

When I got the car back there were a few wires that were installed incorrectly mainly earth wires on the passenger side headlight. Once this was fixed by myself and the earth wires connected to the right areas I noticed the oil pressure gauge started to work, this only lasted a few days and it hasnt worked since.

So I am sure the gauge is working and that it is a problem relating to the sender but not absolutely sure. Here's a pic of my sender or senders, I have no idea why there are 2 and which one is the one thats supposed to be working. Hopefully you guys can help with how to fix this otherwise it will be back to the Auto Elect.

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#2 _434LX_

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Posted 19 August 2013 - 10:52 AM

The only reason I can see for a second sender, is for a seperate electric oil press guage. :dontknow:

If it is a pressure switch, then it may be for electric fuel pump circuit.

The standard oil pressure circuit is a blue wire and from your photo, the correct sender is the one on the right (with blue wire).

Trace that green wire back to the harness plug, work out if it is an addition or runs to the plug.

The green wire from the harness plug should be for the water temp sender.

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#3 _434LX_

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Posted 19 August 2013 - 10:54 AM

Oh, and looking at the photo....

Crimp the connector properly on to the blue wire. It looks like its just jammed under it.

At least you can eliminate that issue.

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#4 _LS1 Hatch_

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Posted 19 August 2013 - 10:59 AM

And....the sending unit needs to ground through the threads...if there is too much stuff gobbed on them (like it sort of looks like with that home made looking T ,that could cause issues perhaps as well. They are NPT threads, so should seal ok as is basically.

(and agree with fixing the terminal being crimped properly onto the wire of course too)

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#5 _LHSL308_

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Posted 19 August 2013 - 02:25 PM

The only reason I can see for a second sender, is for a seperate electric oil press guage.

If it is a pressure switch, then it may be for electric fuel pump circuit.

The standard oil pressure circuit is a blue wire and from your photo, the correct sender is the one on the right (with blue wire).

Trace that green wire back to the harness plug, work out if it is an addition or runs to the plug.

The green wire from the harness plug should be for the water temp sender.

Your right the car had an additional oil pressure gauge when I bought it. I removed it when I changed the dash over. I bought some new connecters today so will fix that issue this arvo. Should I just remove that stupid extension all together and just screw the sender unit straight into the thread?

You could also be right Jeff about the teflon tape on the threads, it did seem like an earth issue.

Edited by Gonedeaf, 19 August 2013 - 02:27 PM.

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#6 _434LX_

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Posted 19 August 2013 - 02:46 PM

Your right the car had an additional oil pressure gauge when I bought it. I removed it when I changed the dash over. I bought some new connecters today so will fix that issue this arvo. Should I just remove that stupid extension all together and just screw the sender unit straight into the thread?

You could also be right Jeff about the teflon tape on the threads, it did seem like an earth issue.

I would lose the Tee, screw the sender in with just a smidge of liquid teflon and fix the wire crimp.

You can test the earthing issue as suggested by Jeff, by holding a wire between the body of the sender and a good earth.

Report back how you go mate.

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#7 _LS1 Hatch_

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Posted 19 August 2013 - 02:47 PM

If I were you, I would get rid of the extension thing and the extra sensor and just screw the factory one back in where it goes.

One less place to worry about leaks if nothing else too

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#8 _LJ Kermit_

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Posted 19 August 2013 - 02:52 PM

apologies for trite observation....

connections are the first thing I look at when faced with a wiring fault.

Wires alone seldom cause problems.

invest in a good quality crimping tool, learn how to use it properly and ensure that any crimps are correct.

generally, clean, neat and crimped properly. do not use side cutters... or any other tool unless you are prepared for the consequences...

i.e. a dodgy connection that will fail soon.

if you can solder the wires then that is also a good connection if done properly...

have seen old GTR panel where there is over 20 Ohms resistance in the crimp so the light did not work properly.

best wishes LJ Kermit

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#9 _LHSL308_

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Posted 19 August 2013 - 04:16 PM

Hi guys,

Got rid of the extension and crimped a new fitting on the wire. Just put a smidge of teflon on the thread and done the sender up nice and tight. Started the car up and took it for a 10 minute drive and the needle didnt even move. If I test the earthing issue the above way what should I expect to see, the gauge moving?

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#10 Rockoz

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Posted 19 August 2013 - 04:47 PM

Earth the wire then have a look at the gauge. It should have moved to full pressure. If not the problem is elsewhere.

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#11 _LHSL308_

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Posted 19 August 2013 - 05:08 PM

Ok earthed a wire from the body of the sender to the engine block earth and needle didnt move but when i earthed the wire from the engine block to the prong that the wire connects to the needle went to full.

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#12 hanra

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Posted 19 August 2013 - 05:23 PM

So you have a faulty oil pressure sender or your engine is not making any oil pressure.

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#13 S pack

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Posted 19 August 2013 - 05:40 PM

So you have a faulty oil pressure sender or your engine is not making any oil pressure.

Haha Brad, you beat me to it.

The gauge needle moving to full or high with the sender wire earthed indicates the sender unit is faulty.

BTW, never connect the sender wires directly to earth on thermal gauges for more than a few seconds, you can quite quickly burn out the dash gauge unit, they do not tolerate O ohms. Always use at least a 10 ohm resistor when doing such tests.

Edited by S pack, 19 August 2013 - 05:41 PM.

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#14 _434LX_

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Posted 19 August 2013 - 06:35 PM

And now when you install the new sender, it will all look schmick !! :buttrock:

Also, as mentioned above, don't go shorting wires out during a diagnosis people. You will cause all sorts of problems for yourself.

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#15 hanra

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Posted 19 August 2013 - 06:38 PM

Yep I think about 15ohms should be full deflection.

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#16 S pack

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Posted 19 August 2013 - 07:24 PM

Yep I think about 15ohms should be full deflection.

The thermal type fuel tank sender units work through a range of 69 ohms (empty) to 10 ohms (full).

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#17 hanra

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Posted 19 August 2013 - 07:43 PM

Your right again Dave. Thank you.

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#18 Rockoz

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Posted 19 August 2013 - 07:57 PM

try the other sender perhaps

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#19 S pack

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Posted 19 August 2013 - 08:14 PM

try the other sender perhaps

Not a good idea if you don't know the ohms range of the aftermarket sender. Could be a really quick way to fritz the SLR oil pressure gauge.

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#20 _LHSL308_

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Posted 19 August 2013 - 09:20 PM

So can you guys point me in the right direction for a new oil sender, 308 Holden V8. Heres hoping I didnt stuff the gauge but I didnt have it on for long. Never mind I think their available through rare spares. Thanks all for your help.

Damn I cant find any on the rare spares website, I hope they still sell them.

Found them $89 holy frOck.

Edited by Gonedeaf, 19 August 2013 - 09:34 PM.