Mercruiser 1999 5.0 carb oil pressure switch

[sskeetr1]

I have a 1999 Mercruiser 5.0 carb motor.
The engine alarm system used to beep once when I would turn the key on, now it wont beep. The alarm has a purple wire and a tan and blue wire, i grounded the tan and blue wire and the alarm sounds. Not sure why I quit getting the quick beep when powering up. Any suggestions? Thanks

 

[Scott06]

I have a 1999 Mercruiser 5.0 carb motor.
The engine alarm system used to beep once when I would turn the key on, now it wont beep. The alarm has a purple wire and a tan and blue wire, i grounded the tan and blue wire and the alarm sounds. Not sure why I quit getting the quick beep when powering up. Any suggestions? Thanks

The alarm switch back on engine is no good it makes the ground connection via the tan and blue wire

There are three switches low oil pressure, engine over temp and low drive lube

They make the ground connection for the buzzer all switches in parallel. When you start the engine the purple wire is energized and for a brief moment until oil pressure gets above 4 or 7 psi the alarm will sound. Engine runs switch opens electrically buzzer goes off

What u describe means your switch is no longer working

 

[alldodge]

What is the serial number of the motor?

 

[sskeetr1]

What is the serial number of the motor?

OL436941.
Its a new crate engine from mercruiser

 

[sskeetr1]

The alarm switch back on engine is no good it makes the ground connection via the tan and blue wire

There are three switches low oil pressure, engine over temp and low drive lube

They make the ground connection for the buzzer all switches in parallel. When you start the engine the purple wire is energized and for a brief moment until oil pressure gets above 4 or 7 psi the alarm will sound. Engine runs switch opens electrically buzzer goes off

What u describe means your switch is no longer working

Im having a couple issues, i dont get the slight beep when energized. I tested switch and tested good. Its a two wire switch at engine, purple wire on NO norm open and tan blue on C. I took out and test continuity across post there was none i put a bit of air in switch and it then gave continuity.

My oil gauge pegs 80 when i start engine and stays there. Brand new oil but figured it would drop to around 30 at idle. I tested sender, its 240 Ohms on the bench. I reinstalled and unhooked wire at gauge and tested. Key on engine off its 240ohms at wire, hook gauge back up and it stays at 80 psi. Turn engine off and key on it drops to zero. Im guessing its the brand new gauge is bad.

 

[sskeetr1]

The alarm switch back on engine is no good it makes the ground connection via the tan and blue wire

There are three switches low oil pressure, engine over temp and low drive lube

They make the ground connection for the buzzer all switches in parallel. When you start the engine the purple wire is energized and for a brief moment until oil pressure gets above 4 or 7 psi the alarm will sound. Engine runs switch opens electrically buzzer goes off

What u describe means your switch is no longer working

It looks like according to my manual there are 3 switches for oil system, one has 1 tan/blue wire for the buzzer (i cant locate) one that has a purple wire and a purple/yellow wire that is down by the sender and oil filter and then the sender its self that has light blue wire its down by the oil filter as well.

 

[04fxdwgi25]

Seems as though there may be some confusion on your wiring.

Here are the Mercruiser wiring diagrams

 

[alldodge]

When using the SN it comes up as a transom assembly but using the range of the number it would be a 1999 TBI with a MEFI 3 ECM. The thread list a carb motor. A carb wouldn't give a short beep when key is turned ON but a TBI would.

The wiring for the switches/sensors is correct for a TBI motor.

Your gauge goes to zero with motor OFF and Key ON, so I would think your gauge is working correctly. Measure the resistance with motor idling, it could be the motor has a high pressure oil pump instead of the standard pump. Could also verify gauge with a mechanical gauge where the sender is

 

[Scott06]

Im having a couple issues, i dont get the slight beep when energized. I tested switch and tested good. Its a two wire switch at engine, purple wire on NO norm open and tan blue on C. I took out and test continuity across post there was none i put a bit of air in switch and it then gave continuity.

My oil gauge pegs 80 when i start engine and stays there. Brand new oil but figured it would drop to around 30 at idle. I tested sender, its 240 Ohms on the bench. I reinstalled and unhooked wire at gauge and tested. Key on engine off its 240ohms at wire, hook gauge back up and it stays at 80 psi. Turn engine off and key on it drops to zero. Im guessing its the brand new gauge is bad.

there are two oil pressure switches one for the fuel pump which has two wires , thus switch cuts off power to fuel pump if ignition is on but engine not running.
the audio warning oil pressure switch will have one wire on it As it is only opening and closing ground leg to block ground. On my engine this switch is up by distributor.
yes sounds like gauge is bad or maybe isn’t getting good power? Easy way to test is at engine take gauge sender wire off and ground gauge should peg if you are pegged all the time gauge would think is no good

 

[tank1949]

I have a 1999 Mercruiser 5.0 carb motor.
The engine alarm system used to beep once when I would turn the key on, now it wont beep. The alarm has a purple wire and a tan and blue wire, i grounded the tan and blue wire and the alarm sounds. Not sure why I quit getting the quick beep when powering up. Any suggestions? Thanks

That old of boat? Replace switch.