Cat 3126 Oil pressure switch and alarm panel.

kvduff

Well-Known Member
Jun 22, 2011
711
Long Island N.Y.
Boat Info
1998 450 Sundancer
Engines
Caterpillar 3126 -420hp
I have had an intermittent issue over the last 2 weeks. The oil pressure alarm triggers on my starboard side, or at other times it will not allow the engine to start. Other times the boat runs fine, oil pressure steady at 50psi, for hours at a time.
I am leaning towards the pressure switch as the issue. The sender is identifiable from its shape and has a single wire. There appears to be two other switches one which has two wires and the other elongated ( seen it referenced as bullet shaped) has three wires.
I had considered starting the engine and unplugging the two wire clip to see if that will replicate the issue. Not sure if that’s the best course to take.
I am trying to determine which switch is intermittently triggering the low oil pressure alarm panel.
 
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I have had an intermittent issue over the last 2 weeks. The oil pressure alarm triggers on my starboard side, or at other times it will not allow the engine to start. Other times the boat runs fine, oil pressure steady at 50psi, for hours at a time.
I am leaning towards the pressure switch as the issue. The sender is identifiable from its shape and has a single wire. There appears to be two other switches one which has two wires and the other elongated ( seen it referenced as bullet shaped) has three wires.
I had considered starting the engine and unplugging the two wire clip to see if that will replicate the issue. Not sure if that’s the best course to take.
I am trying to determine which switch is intermittently triggering the low oil pressure alarm panel.

while the dash is reporting low pressure what is the engine mounted oil pressure gauge reading?
 
There is a oil pressure switch and an oil pressure sender on these engines. The switch is for the SR Systems Monitor and the sender is for the helm gauge. The sender is a single wire that is a ground bias for the gauge. The switch has two wires in which one is grounded. I can't remember but the switch either goes to ground or opens up when oil pressure raises to a minimum set point. With ignition on and engines not running your SR Systems Monitor should display low oil pressure warning. So if you are getting the warning on the SR Systems Monitor but the gauge shows nominal oil pressure when the engine is running then either the pressure switch or pressure sender or pressure gauge is a problem. If the sender or gauge is the problem then you probably have a real oil pressure issue.....
 
There is a oil pressure switch and an oil pressure sender on these engines. The switch is for the SR Systems Monitor and the sender is for the helm gauge. The sender is a single wire that is a ground bias for the gauge. The switch has two wires in which one is grounded. I can't remember but the switch either goes to ground or opens up when oil pressure raises to a minimum set point. With ignition on and engines not running your SR Systems Monitor should display low oil pressure warning. So if you are getting the warning on the SR Systems Monitor but the gauge shows nominal oil pressure when the engine is running then either the pressure switch or pressure sender or pressure gauge is a problem. If the sender or gauge is the problem then you probably have a real oil pressure issue.....
I dont believe I have true low oil pressure issue. The engine runs perfectly, and has alarmed running at 2250rpm, oil was at 50psi, and it shut the engine down. Another time, it wouldnt allow the engine to start, turned off batteries and turned back on, and engine fired right up... gauge on the engine is reading the same as the dash gauge while running and at idle... I am fairly confident it is a switch issue, going to pick up one today and swap this weekend. Just looking to see if it is the two wire or three wire switch
 
Could be a switch or just a loose/corroded wire.
 
The more I think about this. I am not sure that the the low oil alarm would actually shit off the engine. When the engine did cut out while operating the ignition start switch was still push forward, possibly triggering the alarm as it would normally do when the switch is on without running. Thinking maybe the relay for the fuel pump maybe getting ready to go out on me. Picked up a new relay for 10.00 and will give that a try before going after the alarm switch.
 
The more I think about this. I am not sure that the the low oil alarm would actually shit off the engine. When the engine did cut out while operating the ignition start switch was still push forward, possibly triggering the alarm as it would normally do when the switch is on without running. Thinking maybe the relay for the fuel pump maybe getting ready to go out on me. Picked up a new relay for 10.00 and will give that a try before going after the alarm switch.
I would agree - I don't believe that low oil pressure or for that matter high coolant temperature will shut these mechanical engines down other than them seizing up. Now, the newer electronic engines have many "safety's" that reduce power or shut down the engine. These are traditional gauge watching engines and not nanny engines.
 
I know this is an older thread butI am having a similar issue with the “low oil pressure warning” not allowing the starboard engine to start. @kvduff what was your fix?
 
on a related note: my systems monitor failed the day of closing so I disconnected it at the dash connection.

I'm too old fashioned to do the Maretron system.

The engine alarms do not work correctly and I will be doing a "work around" shortly to restore them.

BEST !

RWS
 

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