911 oil pressure shows 100 psi BEFORE starting engine, - Guage wiring??? where to start?? Options

[BKLA]

My '75 914 2.7 conversion has the getty 911 dash and 911 guages. Ever since I purchased the car, in early may, the oil pressure guage has registered 100 psi when I turn on the key and stays there. The oil pressure light comes on but then goes out after the engine warms up a little.

Where do I begin to chase this down?

- the back of the guage?
- the sender unit?

Could the guage be bad? if so, how do I check it?

If the sender unit is bad, how do I check it?

Just looking for a little help on where to start looking....

Thanks!

[bd1308]

you need to hook it up...I think it will peg to max if disconnected.

If a 914 engine with the stock sensor, you'll need to buy a dual sender for the 914 engine.

one side is for the idiot light (on or off) and one is for the guage (analog output)

b

[Cap'n Krusty]

you need to hook it up...I think it will peg to max if disconnected.

If a 914 engine with the stock sensor, you'll need to buy a dual sender for the 914 engine.

one side is for the idiot light (on or off) and one is for the guage (analog output)

b

Excuse me? Did you even read the question? It's a 2.7 conversion, and the gauge pegs key on, engine not running. There's a wire off at either the sender or the instrument, unless he has a dead sender. And you wonder why they call me Cap'n Krusty ................................

[bd1308]

you need to hook it up...I think it will peg to max if disconnected.

If a 914 engine with the stock sensor, you'll need to buy a dual sender for the 914 engine.

one side is for the idiot light (on or off) and one is for the guage (analog output)

b

Excuse me? Did you even read the question? It's a 2.7 conversion, and the gauge pegs key on, engine not running. There's a wire off at either the sender or the instrument, unless he has a dead sender. And you wonder why they call me Cap'n Krusty ................................

I cnt rd

[BKLA]

you need to hook it up...I think it will peg to max if disconnected.

If a 914 engine with the stock sensor, you'll need to buy a dual sender for the 914 engine.

one side is for the idiot light (on or off) and one is for the guage (analog output)

b

Excuse me? Did you even read the question? It's a 2.7 conversion, and the gauge pegs key on, engine not running. There's a wire off at either the sender or the instrument, unless he has a dead sender. And you wonder why they call me Cap'n Krusty ................................

I'll check the back of the gage tonight. I'll also check that the sender is a dual unit - I had assumed that it was because the idiot light worked.

SHould it not be a loose wire, is there a way to use a multi-meter on the sender to check it? (Sorry, I am an idiot when it comes to electrical stuff...) what should the meter setting be as well as its readings? If the sender is good then I'll need to check the wiring, I assume...

Thanks!!!!!!

[Dave_Darling]

The 911 engine will have two separate senders. Not a bad idea (two redundant sensors for something that is so critical).

Find the sender for the gauge (sorry, I don't remember where it is!) and unplug the wire. Then unplug the wire at the gauge. Check the resistance from the one end to the other; you should see very close to 0 ohms. Then check the resistance from either end to ground. You should see whatever your meter uses for "infinity" or "no connection". If either of those tests fail, the wire is bad.

I believe the 911 gauge works like ours does--the sender is a gizmo whose resistance changes when pressure is applied to it. If that is indeed the case, then you can check the resistance from the plug-in part of the sender to ground. Make sure that number changes when the oil pressure changes (i.e., engine off to engine running).

After that, you can fake up a sender by using a potentiometer (a knob connected to a variable resistor). That will at least let you test the gauge.

--DD

[BKLA]

The 911 engine will have two separate senders. Not a bad idea (two redundant sensors for something that is so critical).

Find the sender for the gauge (sorry, I don't remember where it is!) and unplug the wire. Then unplug the wire at the gauge. Check the resistance from the one end to the other; you should see very close to 0 ohms. Then check the resistance from either end to ground. You should see whatever your meter uses for "infinity" or "no connection". If either of those tests fail, the wire is bad.

I believe the 911 gauge works like ours does--the sender is a gizmo whose resistance changes when pressure is applied to it. If that is indeed the case, then you can check the resistance from the plug-in part of the sender to ground. Make sure that number changes when the oil pressure changes (i.e., engine off to engine running).

After that, you can fake up a sender by using a potentiometer (a knob connected to a variable resistor). That will at least let you test the gauge.

--DD

Thanks Dave!!! (IMG:style_emoticons/default/clap56.gif)

[dimitri]

911 usually have a combination sender for light and pressure, hate to disagree.
The unit sits right next to the oil thermostat, close to breather at the flywheel side.
Its a pot about 1.5" in dia and almost 2' tall. You can still check resistance. Dimitri

[Dave_Darling]

I thought it was two separate ones... At least on some years--I'm starting to remember seeing a Panorama article about this. I don't remember which years, though.

--DD