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sparky · Joined: 27 Nov 2002 Posts: 772 Location: Malta

The title pretty much describes it all..

When I flick the ignition on the oil pressure gauge pegs to max (10bar+).

So the idiot light does work properly and the gauge is connected to the G output on the oil pressure sender. The gauge itself has 12v on ignition on, the +ve feed is goiing to +, the ground is going to the ground symbol and the G is connected to the G on the sender unit..

I switched the G and Ground symbol terminals on the gauge, "just because" and it flicks on just below 0 and stays there. Probably a useless bit of info, but thought would add everything.

Ive done the normal searches which suggests possible shorts ect. I checked the wire going from the gauge to the sender, there are no shorts to ground on this circuit and I also checked the wire and all is intact.

I do remember the gauge working before it went in for some work ages ago. Could a dud oil pressure sender give this symptom? Welding killed something? Or is there something else I am missing/have not checked?

Cheerz all,
Sparkz
_________________
When the checkered flag drops... The Bull$hit Stops

1976 Euro 924 (The 945)

- Full 951 Brakes/Suspension

1998 Boxster with goodies
2002 3.0 Xtype 4wd sport

924RACR · Posted: Fri Mar 11, 2011 1:56 am Post subject:

Welding shouldn't kill that; if everything's been thoroughly checked, then perhaps it is indeed the sender...

Is the resistance between the sender "G" terminal and ground (threads of the sender) in fact 0?
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

gohim · Joined: 02 Nov 2002 Posts: 4459 Location: Rialto, CA

The sender is probably screwed up. Infrequent oil changes result is gunk settling in the oil pressure sender causing it to screw up. The one on my 81 924 did that when I bought it in 88 for about two years until scheduled oil changes allow it to be flushed out, and start working properly. Haven't had a problem since then.

sparky · Joined: 27 Nov 2002 Posts: 772 Location: Malta

Yeyo,

Would gunking up cause it to max out to full on gauge though? The car has not really done too many miles since it got back on the road, I would say about 600 max since the oil sender was fitted.

When I checked, there was no passage from the G terminal to ground which if there was I would expect would cause the needle to peg so im a little lost..

Unfortunately the sender from the 928 engine I pulled is different, but what other cars use the same sender unit correct to the 10 bar gauge that I can pick up if it turns out to be a dud sender?

Cheerz
_________________
When the checkered flag drops... The Bull$hit Stops

1976 Euro 924 (The 945)

- Full 951 Brakes/Suspension

1998 Boxster with goodies
2002 3.0 Xtype 4wd sport

gohim · Joined: 02 Nov 2002 Posts: 4459 Location: Rialto, CA

Yes it can. That's exactly what mine did for a couple of years. I think what happens is the gunk traps the initial engine start pressure inside of the sender.

Frequent oil changes with a quality oil with plenty of detergent cleaned out the gunk for me after a while, and the gauge has read perfectly since.

924RACR · Posted: Fri Mar 11, 2011 11:05 pm Post subject:

So what you're describing, the gauge should be pegged whether or not it's plugged in to the sender. Can you verify this?

If this is the case... then you do have a short to ground in the wiring harness...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

sparky · Joined: 27 Nov 2002 Posts: 772 Location: Malta

Hmmm Weird, disconnected the G terminal from the sender, still pegged, so removed the wires from the gauge to pass a new one, oh what? STILL PEGGED.

So with the +12v connected to the + on the gauge and the ground connected to ground with no signal cable attached, the gauge still pegs, any clues?
_________________
When the checkered flag drops... The Bull$hit Stops

1976 Euro 924 (The 945)

- Full 951 Brakes/Suspension

1998 Boxster with goodies
2002 3.0 Xtype 4wd sport

924RACR · Posted: Sat Mar 12, 2011 11:45 pm Post subject:

You probably have to disconnect the power to let the gauge reset... I think I've seen this behaviour before.

Then try seeing if it's pegged without the sender plugged in, but with the gauge fully connected.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

sparky · Joined: 27 Nov 2002 Posts: 772 Location: Malta

Hey buddy..

Gave that a try, no matter what the gauge pegs, tried doing the above with no luck, fair to say the gauge is shot i guess?

Cheers

_________________
When the checkered flag drops... The Bull$hit Stops

1976 Euro 924 (The 945)

- Full 951 Brakes/Suspension

1998 Boxster with goodies
2002 3.0 Xtype 4wd sport

MRPETE · Joined: 07 Nov 2010 Posts: 67 Location: CALGARY AB CANADA

I had the same issue with mine(after I did some welding by the way)My meter would peg and stay there.If I turned of the car and tapped the gauge it would go to 0 I took the wire off the sender and tried again can't remember if it pegged or not but then connected sender wire to ground.One way the meter should stay at 0.Bottom line my sender was shot.Got one from a boneyard Audi or something 2 bucks hope this helps Pete
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"81 924
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sparky · Joined: 27 Nov 2002 Posts: 772 Location: Malta

MRPETE · Joined: 07 Nov 2010 Posts: 67 Location: CALGARY AB CANADA

Nope It's the sender!Off to the boneyard pretty sure I got mine off an Audi
Pete

Do you go tothe dirty dick bar?
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'77 924
"81 924
Lots o' Corvairs

924RACR · Posted: Sun Mar 13, 2011 11:09 pm Post subject:

924RACR · Posted: Sun Mar 13, 2011 11:10 pm Post subject:

Hang on... is this a 2.0L 924 or maybe a 2.5L/late car?

They're rather a bit backwards in the wiring compared to a 2.0L/early car...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

sparky · Joined: 27 Nov 2002 Posts: 772 Location: Malta

Its the 2.0 924, the power wiring is dead simple, +12v, ground and gauge, it must have somehow shorted inside the gauge, I agree it would be strange that welding on the car caused this, but the alarm box did also half die at the same time (which does not surprise me)

Ill pick up a gauge in the coming days and confirm this

Cheerz all

_________________
When the checkered flag drops... The Bull$hit Stops

1976 Euro 924 (The 945)

- Full 951 Brakes/Suspension

1998 Boxster with goodies
2002 3.0 Xtype 4wd sport