1988 MOTOR IN EXCELLENT ORDER FROM ONLY FRESHWATER USE, BUT CAN'T STOP OIL ALARM. ORIGINAL FAULT WAS AN ALARM ONLY WHEN MOTOR (AND OIL CONTROL MODULE WAS HOT) DIDN'T EVEN GET THE INITIAL BLEEP WHEN TURNING THE KEY SWITCH ON UNTIL THE MODULE WAS HOT. WHEN HOT THE ALARM CAME AND WENT IF THE MODULE WAS GIVEN A SHARP TAP AS SUGGESTED IN THIS FORUM. REPLACED THE OIL CONTROL MODULE AND NOW THE ALARM BLEEPS HOT OR COLD AS SOON AS THE ENGINE FIRES UP. CHECKED THE OIL FLOW METER WITH OSCILLOSCOPE,WHICH OUTPUTS A SQUARE WAVE WHICH ALTERS WITH ENGINE REVS. REPLACED THE OIL FLOW METER WHICH MADE NO DIFFERENCE TO THE FAULT. PLENTY OF OIL IN THE TANK ON TOP OF MOTOR AND FLOAT SWITCH APPEARS TO WORK OKAY ,ALTHOUGH IF BYPASSED AND EARTHED OUT (AS IF THE OIL LEVEL WERE LOW) THEN ALARM STOPS FOR ABOUT 10 SECONDS AND THEN COMES BACK. THERE IS ABOUT 20 MEGAOHMS RESISTANCE ACROSS THE FLOAT SWITCH WHEN CONTACTS OPEN (FLOAT UP) DON'T KNOW IF THIS IS INCORRECT.
Woodman, that oil motion sensor input is compared to an input from the ignition system...if they dont compare, alarm fires. are you losing your ignition input?
Really appreciate your help ODDD1. I will put my scope on the input to the oil control module from coil 4. Do you know if I can change this input from coil No.4 to a different coil, or is the synchronisation between coil 4 and the oil motion sensor important ? Thanks again.
G'Day. Do you have spark on cyl no. 4.If you have no spark then the alarm will sound. The oil sensor registers when a magnet that is fitted to the oil drive shaft passes a sensor. If this magnet has not been fitted properly then the alarm will sound. Remove the oil pump and the shaft. Remove the magnet and then refit it the other way round. that is the other pole will be facing out. See if this fixes the problem.
Thanks to all who have replied. Have run the motor again for an hour. There is a very strong spark on all cylinders. I don't think the synchronisation between coils and oil motion sensor can be important because that oil pump shaft ,with the gear and magnet on ,can be inserted into the engine in a number of positions. The original magnet was a 2 piece loose item,(cylinder plus hemisherical piece) but with the new motion sensor you also get that nylon bush that is driven by the oil pump shaft. The magnet is now supplied encapsulated into this with resin so you can't turn it round any more.I've connected the green wire (from #4 coil to oil control module) to all six coils in turn and still the alarm goes off as soon as the engine fires. The rest of the wires from the oil control module have the following voltages. Purple 12.4v, Brown is a square wave between 12.4v and zero, it activates the warning buzzer when it is low, so it's pulsing all the time.Blue 4.4volt output to normally open float switch, Blue & White 4.4volt square wave pulsed input from oil pump, White 9.6volt supply to motion sensor, Black to earth. Assume these are all correct.I'm still suspicious of the signal from the ignition coils , which is a 128volt pulse that lasts for just 5us (0.000005 seconds). Assume this is used to charge a small capacitor within the oil control module, but it seems a very short pulse. Does anyone have any ideas where to go from here ? I'm inclined to agree that it's an ignition related problem. How can I test the primary ignition circuit ?
G'Day. Mmmmmm, Interesting problem, have you tried the oil warning wire from the warning module on the other switchbox. also had a problem once on one of these where the float in the oil tank was sinking. Try running the motor with the float tied into position. Some of the early motors had a problem where the sensor for the magnet on the movement sensor was too close to the magnet. try putting a thin metal washer underneath the movement sensor.
Whaley, thanks for your advice I will try the float switch modification as suggested and perhaps even fit a new float switch. Is it okay to just unplug the float switch as it's contacts are normally open to ground, or have Mercury been clever and built in some critical level of resistance across the open contacts to trigger the alarm if the float is unplugged.... If they have perhaps this resistance is now incorrect and is causing the alarm. Does anyone know if a good engine sounds the alarm if the blue float switch wire is unplugged ? Also can you tell me where the oil warning wire from the other switchbox is located. There is a two wire switchbox on top of the engine block which I assume is a voltage regulator and there is another small module on the starboard side. The Clymer manual gives no wiring diagram for any of this. Thanks again for your help.
G'day. The switchbox is the CD unit on the stbd side of the motor, there is a green wire from theoil module that goes to one of the coil terminals on the switchbox. You will find another switchbox behind the first. Remove the outer switchbox and fit the green wire to the center coil wire on the inner switchbox.
The magnet in the motion coupler could be in backwards. The end of magnet that attracts the North Arrow of compass is inserted into the coupler first. The output of motion sensor should peak at 5 volts, then dropping to less then 1 volt every 2 revolutions, turn engine with emerg start rope with plugs out, this from 1992 manual. Did not say which meter to use, but ignition ouout is check with peak reading meter. Primary voltage at coil must be within specs, 90 to 240 volts with peak reading meter depending on rpms, also from 1992 manual.
HAVE FOUND THE PROBLEM AT LAST. THE SHAFT THAT DRIVES THE OIL PUMP IS (I AM TOLD) DRIVEN OFF A GEAR ON THE CRANKSHAFT. THE CRANKSHAFT GEAR IS EITHER WORN OR SLIPPING ON THE CRANK....STRANGE AT ONLY 300 HRS USE FROM NEW. I CAN EASILY PREVENT THE OIL PUMP SHAFT FROM TURNING (INSERT A SCREWDRIVER IN THE END OF THE PLASTIC COUPLING) AS THE ENGINE IS TURNED OVER BY HAND. THE OIL PUMP SHAFT GEAR IS IN GOOD CONDITION SO THE PROBLEM MUST BE WITH THE CRANKSHAFT GEAR. IT SOUNDS LIKE A LOAD OF LABOUR TO GET AT THIS GEAR. THIS EXPLAINS WHY THERE WAS AN OUTPUT FROM THE OIL PUMP MOTION SENSOR, WHAT I DIDN'T KNOW WAS THAT THE OUTPUT WAS NOT MATCHED TO ENGINE REVS BECAUSE THE SHAFT WAS SLIPPING. HAS ANYONE SEEN THIS PROBLEM BEFORE ?
MARINER 135 V6 OIL ALARM
The oil sensor registers when a magnet that is fitted to the oil drive shaft passes a sensor. If this magnet has not been fitted properly then the alarm will sound. Remove the oil pump and the shaft. Remove the magnet and then refit it the other way round. that is the other pole will be facing out. See if this fixes the problem.
Linear Mode
