Volvo oil pressure reads 80 psi all times

[Driberich]

I have a 2005 four winns with a 5.0 GL VOLVO. The boat is new to us. The oil pressure reads 80 psi when ignition is on but not started. ( drops to about 30-40 when off) It also reads 80 psi when started. A boat mechanic replaced the gauge but still reads 80. I checked the ohms at the sending unit and off the engine it reads 250. Installed it reads 250 but when key ignition is on, it drops to 33 ohms (making the gauge read 80 psi) I have tried a new sending unit with the same results.

Just for reference, I hooked a mechanical gauge to the engine and it reads 50 psi at idle and increase as the rpm’s do.

Boat mechanic says the older anolog gauges read inaccurate and nothing can be done. ( I just have to live with it)

Any insight on this???

 

[alldodge]

With gauge reading 30-40 when off my first suspect is the gauge. Did the gauge really get changed or it was just said it was replaced. My guess is gauge was not replaced.

If it actually was, check the ground on the gauge. See if there is a difference between Bat Gnd to gauge ground by placing meter between Bat Gnd to gauge Gnd

Does voltage go above 14.5V when running?

 

[Driberich]

With gauge reading 30-40 when off my first suspect is the gauge. Did the gauge really get changed or it was just said it was replaced. My guess is gauge was not replaced.

If it actually was, check the ground on the gauge. See if there is a difference between Bat Gnd to gauge ground by placing meter between Bat Gnd to gauge Gnd

Does voltage go above 14.5V when running?

The gauge was indeed replaced as it’s a different cluster of gauges than when we got the boat. I would have to check the voltage when running. Should I check voltage at the gauge? The old gauge read the same 80psi hence why we brought the boat in for repair.

 

[alldodge]

Main concern is the non-zero when things are off.

Check V while running and off at gauge

 

[Driberich]

Main concern is the non-zero when things are off.

Check V while running and off at gauge

Would checking the volts matter because the gauge responds by ohms and not volts from the sending unit?

 

[alldodge]

Would checking the volts matter because the gauge responds by ohms and not volts from the sending unit?

The gauge should go to zero unless the gauge is designed not to go to zero, gauge is bad (2nd one was used and not new), or voltage is being applied when off. The resistance (ohms) reduces the amount of current that goes thru the gauge. The more resistance the less current,

You've already proven the gauge is reading incorrectly, just trying to find out why.

Have you tried to remove the lead on the sender and does it go to zero?

 

[Driberich]

The gauge should go to zero unless the gauge is designed not to go to zero, gauge is bad (2nd one was used and not new), or voltage is being applied when off. The resistance (ohms) reduces the amount of current that goes thru the gauge. The more resistance the less current,

You've already proven the gauge is reading incorrectly, just trying to find out why.

Have you tried to remove the lead on the sender and does it go to zero?

Yes I have removed the lead and the psi still shows 80psi. It does this with the engine on or off with the key on. It returns to 30-40 with key off.

 

[alldodge]

The sender wire might be chuffed. If it does the same with sender wire disconnected at the Gauge then I'm back to voltage reading

 

[Driberich]

Ok I’ll check that. Thanks for the advice!

 

[Scott Danforth]

FWIW, check the ground to the gauge

also, I have a mechanical gauge installed on the engine and the electric gauge in the dash. both read pressure, however the electric one reads about 25% high. I have the low oil pressure switch to kill ignition and fuel should my pressure drop below 7psi

 

[QBhoy]

Wonder if the sender and or gauge are miss matched between the European and Us types. One reads from minimum ohms up and the other from higher ohms down.

 

[Driberich]

When we bought it, it had the original gauge and the original sending unit. I would assume both these worked fine from the factory. We got the boat last year in the cage has been replaced and I have tried another sending unit with the same results.

 

[Driberich]

It is strange because when I disconnect the wire from the sending unit, the gauge will still read 80 psi. But when I leave the sending unit hooked up and I turn the ignition off the pressure reading goes down to about 30 to 40 psi.

 

[Driberich]

I should also note the oil pressure is in the gauge cluster consisting of water, oil, fuel, and voltage. So all the other gauges worked fine meaning that it probably is not a voltage issue leading to the gauges since all the other gauges read as normal and function properly.

 

[QBhoy]

It is strange because when I disconnect the wire from the sending unit, the gauge will still read 80 psi. But when I leave the sending unit hooked up and I turn the ignition off the pressure reading goes down to about 30 to 40 psi.

Is 80 psi the maximum reading on the gauge ? I may be getting mixed up in my post earlier. Was attempting to multitask…badly ! I was thinking more around fuel gauges. The same may apply to oil pressure too, I suspect.
If I’ve got it right off the top of my head…the US senders should read about 240/250 ohms when the gauge is showing the minimum reading…and close to 0 when the gauge shows the maximum reading.
Here in the uk it’s almost but not quite the opposite. Something like 30-190/200 ohms corresponds to minimum to maximum reading on the gauge.
If the gauge is European and the sender US, you’d get a bad reading.
But I don’t think this is the case for you, after a think.
So you’ve found a reading of 250 when at rest, but with ignition on, you’ve found a reading of about 30 ohms ? If that’s the case, then the sender isn’t working properly I think. If the ignition is on and engine isn’t running and producing oil pressure, you should still find a reading closer to the 250ohms. If it’s showing 30 ohms or close in this state, the gauge will show a high or maximum reading.
I wonder if your wiring is shorting together somewhere along its length.
Just a final thought. Is your engine one of the models that has the fuel pump triggered by an oil pressure switch ? Should be entirely separate, but thought I’d ask

 

[alldodge]

cold / hot
240 / 33 North American
0 / 180 European

 

[Driberich]

Oil sending unit reads 250 ohms which is matched to the oil gauge. While having the mechanical gauge hooked up I left the wire on the sending unit which had no pressure and the gauge still read 80 which is the max on the gauge. Somehow when the ignition is on it’s making the gauge read 80 regardless of the engine is running or not. It did this with the old gauge as well.

 

[alldodge]

There is a very easy (kind of sort or maybe) way of figuring this out.
Get a hold of any electrical stand alone Temp gauge ( probably could use other gauges but lets not get into that right now ) and connect the Temp sender to it with power and ground. If it reads correctly then its the gauge, if not then the rapture is coming

 

[QBhoy]

I think your wires must be shorting somewhere near the gauge, when the ignition is turned on

 

[Driberich]

I’m going to pull the gauge and troubleshoot. If not, I’ll live with it since I already paid $300 on the new gauge and install.