Only three plugs sparking

[Thomas Perkins]

I have a 1985 175 horse 6 cylinder Mariner motor. My oil injection warning went off {fast intermittant} and I discovered a busted fuel line inside the motor. I replaced the fuel line, but alarm continues. The sensor in the internal resevoir checked out fine, as did the sensor for the oil pump, so I proceeded to check and see if I was running on all six cylinders. The three plugs on the starboard side are firing great, but the three on the port side won't fire. Plugs are brand new. There are three power packs, each controlling one plug on the port side and one on the starboard. Is it the ignition switch causing me this headache? Any other ideas? Thanks.

 

[achris]

Re: Only three plugs sparking

Hello Picard,<br /><br />Welcome to iBoats.<br /><br />Slight correction to your thinking is required. You have 2 switch boxes (power packs) located on the starboard side of the engine. Those 'packs' you are looking at on the back of the engine are coils, there are six of them. You are seeing the spark lead coming for each coil, which are under a cover. <br /><br />Ok, on to the real problem. One of the sensors the oil warning module looks for is a spark, from one of the coil primary wires on a switch box. It is checking engine speed with the rotational speed of the oil pump drive shaft, using a 'hall effect' sensor. If you loose spark on that cylinder the oil warning module thinks you have an oil supply problem (you do have a problem, but it's not oil). <br /><br />You can loose spark on one bank for 2 reasons. Dead switch box or dead stator. One can determine which by swapping the switch boxes and seeing if the fault follows the box or stays with the stator.<br /><br />Chris.............

 

[Thomas Perkins]

Re: Only three plugs sparking

Did what you said, and it turned out to be the switch box. Many many thanks.