Oil pressure switch / oil pressure sender

[Kwanza]

Hi all,
I am investigating previous sudden and clean shutoffs of my VP 3.0 GLP engine. Initially, I suspected fuel pump being shut down by a struggling alternator and a potentially failing bilge blower, this latter knocking down both dashboard and multimeter voltage reading from 14V to 12V while running, or from 12V to 10V on the ON position. This bilge pump has now been replaced, with both dashboard, multimeter and Garmin Striker voltage showing ~13.9 - 14.3 V while cruising at ~2800-3000 RPM; with bilge blower, if turned on, dropping voltage by less than 0.5 V.

I now suspect that my oil pressure safety switch might be the culprit.

Few days ago, I returned from an ~8 km trip, running smoothly at ~3000 RPM. Took boat home and parked it in driveway, then attempted to rinse the engine, but it would not start. This was approximately 30 minutes after shutting engine down. I was hoping that a potentially overheated oil safety switch or fuel pump relay are playing up and would start later.

I've tried starting a few times since, to no avail. Lanyard safety switch on, and there is spark.
Trying to listen to fuel pump humming is difficult, as I have a default continuous alarm while on the ON position.
Firstly, I need to know which one of A and B is the oil pressure gauge sender, and which one is the oil pressure safety switch (that could potentially disable my fuel pump). Wire color on A is blue, on B is light brown.

My gauge usually indicated between 20 - 40 PSI oil pressure. As I now attempt to start, and engine keeps turning over but not starting, oil gauge works up to same ~40 PSI over the ~5 seconds I attempt the start.
I did bypass what I thought was the oil pressure safety switch, connecting B to C. Still no start.

Resistance measurement values are:
Between B and C (or between B and other ground points): 4 Ohms, with brown wire on or off the spade.
Between A and C (or between A and other ground points): 252 Ohms when blue wire removed from threaded stud, 144 Ohms with wire on.

Are these values indicating anything
Single engine, single sender.

Any suggestion as to what to try next is welcome.
Thank you.

 

[Scott Danforth]

A is your gauge sender. It only controls the gauge
B is the wire off the oil switch
C is the oil fitting for the oil switch

The switch between Band C is a binary mechanical pressure switch

Your measurements are meaningless

You should be looking for a bad connection, most likely the block ground or the main fuse at the starter

 

[alldodge]

and there is spark.

The GL series motors use switches to apply a ground to turn ON the alarm, they have nothing to do with spark or fuel

Your motor uses a relay to energize the fuel pump. The pump is energized from power supplied by a Yel/Red wire coming from the key while cranking going thru a diode. The run side comes from the Alternator by a Green wire thru another diode.

Right now I don't see it being the diodes so start with the relay and it's connections

This is a GL-E

 

[Kwanza]

Thanks everyone. It looks like this time I might have a carburetor issue.
While previous shutoffs were all sudden and clean, no spluttering, the latest no-start had a little splutter and running for a second or two while key on start. Looking down my carburetor throat and advancing the priming manually, I could initially see a faint spray, but nothing now.
Is it possible to temporarily disable the default alarm on the ON position, just to try to listen to the fuel pump?

Thank you.

 

[Fun Times]

Disconnect the connector wire B in your photo as that should stop the horn....Or find the horn under/behind the helm/dash area and unhook a wire there...Or some will put tape over the horn speaker to get it toned down.

https://www.ebay.com/sch/i.html?_nkw=3817974&_sacat=0&_from=R40&_trksid=p2322090.m570.l1313

 

[Fun Times]

That carburetor appears very dirty and corroded possibly indicating water at some point got in there... Might be time for a carb tear down, inspection and rebuild.

 

[Kwanza]

Thank you.
That indeed stopped the alarm, and I can now listen when I turn key from OFF to ON. I can hear a single faint click from around the fuel pump every time I turn key to ON, no humming, no turning noise. I suppose I should hear a humming of the pump. If my engine has an electrical fuel pump as I assume and been told, and not a mechanical one, that is.

 

[Fun Times]

Thank you.
That indeed stopped the alarm, and I can now listen when I turn key from OFF to ON. I can hear a single faint click from around the fuel pump every time I turn key to ON, no humming, no turning noise. I suppose I should hear a humming of the pump. If my engine has an electrical fuel pump as I assume and been told, and not a mechanical one, that is.

You have a mechanical fuel pump... It's the one with the yellowish hose running to it / to the left of the white oil filter.
How about an overall view of the engine.

 

[Kwanza]

You have a mechanical fuel pump... It's the one with the yellowish hose running to it / to the left of the white oil filter.
How about an overall view of the engine.

Thank you. Another couple of images of the engine attached. Yes, that's the only place I have hose/tube coming from to the carburetor.
Since I have no fuel reaching the carburetor upon manual priming (with the throttle control or right on the carburetor), I'll have to investigate anti syphon valve, fuel pump, fuel lines. Fuel filter was changed few weeks ago by my mechanic, only did a single three quarter of hour trip since then.

I understand an electric fuel pump could potentially be shut down as a safety procedure by a struggling alternator or a faulty / overheating relay for example.
Would that apply to a mechanical pump as well, or if the pump is not working then it is bad. Assuming rest of fuel system (anti syphon valve, fuel lines) is ok?
Thank you.

 

[Fun Times]

No real safety features to it per se because if the engine isn't turning the pump is not being activated via the pumps arm inside the engine block.
Here's your pump, https://www.volvopenta.com/shop/0/part-sections/54168662?hintPhrase=&hintType=None

Carb, https://www.volvopenta.com/shop/0/part-sections/54142663?hintPhrase=&hintType=None

Though I believe there should be one more letter after your 3.0 GLP-?, that you should try to find to know for sure, here should be all your engine parts, https://www.volvopenta.com/shop/0/search?ft=3.0GLP

Maybe pull the fuel filter to see if there's still fuel in the area and no debris plus carefully see if you're getting fuel to the carb at the fuel inlet line that connects to the carb... You need to know if you're working forward towards/inside the carb or all the way back down to the fuel tank...

 

[Kwanza]

No real safety features to it per se because if the engine isn't turning the pump is not being activated via the pumps arm inside the engine block.
Here's your pump, https://www.volvopenta.com/shop/0/part-sections/54168662?hintPhrase=&hintType=None

Carb, https://www.volvopenta.com/shop/0/part-sections/54142663?hintPhrase=&hintType=None

Though I believe there should be one more letter after your 3.0 GLP-?, that you should try to find to know for sure, here should be all your engine parts, https://www.volvopenta.com/shop/0/search?ft=3.0GLP

Maybe pull the fuel filter to see if there's still fuel in the area and no debris plus carefully see if you're getting fuel to the carb at the fuel inlet line that connects to the carb... You need to know if you're working forward towards/inside the carb or all the way back down to the fuel tank...

Thank you, great help!
I'll start tomorrow by adding another 20 liters of fuel...gauge shows half, but who knows? Only got the boat a few months ago, and always kept fuel above the half mark, where it currently sits. The gauges are quite old, most of them behave, except the RPM that occasionally jumps without any throttle change, needing either a small knock on the front or a wiggle of the cables in the back to settle.
Then, onto the fuel line.
3.0 GLP-D, yes.