How to test low warning oil system (1993-115 Mariner 4cyl)

The low warning oil alarm did not turn on and I ran out of Oil......The same old song.

The two middle pistons took the worth of it and the ouside one not even a scratch.Will be putting it all together with new parts
and was wondering if anyone has some info on to how to test and make sure that the low oil warning alarm is woking ok, from
the Oil tank to the module and to the Alarm..

Thank you

Pro

PS: Ya I know, why didn't I checked the oil by the side of the motor.....kick me please.

Re: How to test low warning oil system (1993-115 Mariner 4cyl)

You have the opposite problem from most people. Their alarms go off when they DO have oil. LOL So you found that you did indeed run out of oil. Main or remote tank? is there is sensor in the tank? Here is the process I used to isolate my bad module. Maybe you can reverse engineer it to see where your problem is.

Run the engine to recreate the conditions sounding the alarm. Do these tests while the engine is running and the alarm is beeping. Be careful- the flywheel is very close to your hand. Keep sleeves, watches and other objects that can catch on the flywheel away. Once the alarm starts, I would first unplug the blue wire from the oil reservoir cap. If the alarm stops, either the oil level sensor is bad or the level is low. Next I would disconnect the green wire going from the alarm module to the #4 coil wire terminal on the switchbox. If this stops the alarm, either the rotation sensor is bad or the pump isn't rotating. If the alarm does not stop reconnect the green wire and unplug the white and blue/white wires to the rotation sensor. If this stops the alarm, check for no spark on #4 cylinder. If the alarm does not stop disconnect the green, white and blue/white wires. If this stops the alarm, then either the pump is not rotating, the rotation sensor is bad, or no spark on #4 or the alarm module is bad. If the alarm still does not stop, disconnect the solid blue, blue/white, white, and green wires, if this still does not silence the alarm, then the alarm module is bad. You will single out a bad component in each step, eliminating each item as you go. You can check the rotation sensor by checking its output. Turn the key on, leave power wire connected and rotate the engine. You should get 1 pulse of 5 volts for every 2 rotations. You'll need to have the plugs pulled for this test so you can turn the engine safelt and easily.

Re: How to test low warning oil system (1993-115 Mariner 4cyl)

The V6's have a rotation sensor on the oil pump and compare pump rotation to an ignition pulse.

The 4 cyl's are much simpler, there is only a float switch in the tank.

There is 'supposed' to be a magnet glued to the bottom of the float inside the oil tank that causes the switch in the bottom of the tank to trigger when the float/magnet gets near.

The usual problem is the adhesive fails and the magnet falls onto or near the switch setting of the low oil alarm.

In rare cases, such as yours, the magnet fell to the side so when the float got low, there was no magnet to set off the switch.

You can test the alarm module by disconnecting the two blue wires beneath the oil tank and connecting them directly together, with the key ON, the oil alarm should sound off.

You can test the switch but that involves pulling the tank loose to get the switch out of its hole in the bottom. Hold a magnet next to the switch with the key ON, the alarm should sound.

The cure is a new tank as it is next to impossible to remove the float, clean it perfectly and re-glue the magnet back on.

Re: How to test low warning oil system (1993-115 Mariner 4cyl)

The oil tank is attached to the outboard motor and there is something at the bottom of the tank.

I think like CharlieB said its only a float at the bottom of the oil tank.

Thank you for the information on how to troubleshoot the oil warning sensor.

Its a lesson that I will not forget. $$$$$

Pro