2005 Mercury 115 ELPTO No Spark

2005 Mercury 115 ELPTO Carb'ed 2 Stroke No Spark. Was running fine on the water then would not start back up. Already replaced all 4 spark plugs, all 4 coil packs, flywheel, and stator. Already disconnected the black/yellow wire at the engine to eliminate any problems at the helm. Not sure what to check next or does anyone have a service manual for this motor by chance?

CLi87 said:

2005 Mercury 115 ELPTO Carb'ed 2 Stroke No Spark. Was running fine on the water then would not start back up. Already replaced all 4 spark plugs, all 4 coil packs, flywheel, and stator. Already disconnected the black/yellow wire at the engine to eliminate any problems at the helm. Not sure what to check next or does anyone have a service manual for this motor by chance?

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You didn't say if it spun up lively with the starter, just wouldn't ignite and run on its own. You need about 200 RPM min. to spin the engine fast enough for the stator to develop enough voltage to light off the plugs.

Does that motor have ADI ignition or CDM ignition? In CDI ignition, the switchbox pulses voltage to the coils to fire the spark plugs. On CDM ignition, the stator powers individual CDI units at each spark plug.

Since you replaced all the likely suspects, except the trigger, you might check for voltage at the switchbox (or CDM units) from the stator.

Chris1956 said:

Does that motor have ADI ignition or CDM ignition? In CDI ignition, the switchbox pulses voltage to the coils to fire the spark plugs. On CDM ignition, the stator powers individual CDI units at each spark plug.

Since you replaced all the likely suspects, except the trigger, you might check for voltage at the switchbox (or CDM units) from the stator.

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I have a 2002 ELPTO 115. It has individual CDIs, different from older switch box engines. Is the ADI ignition the switch box or something after 2002?

ADI refers to alternator driven ignition. They consist of a stator, one or two switchboxes, a trigger and one coil per cylinder. They appeared in the mid 70's on 3 and 4 cylinder motors, and by late 1979 were on all larger motors.

CDM ignition consists of a stator, a trigger and one coil/CDI unit per cylinder. It is similar to automotive ignitions, where the coil packs are powered by battery feed and fired by pulses from the ECU. These units are newer than the ADI style.

Chris1956 said:

ADI refers to alternator driven ignition. They consist of a stator, one or two switchboxes, a trigger and one coil per cylinder. They appeared in the mid 70's on 3 and 4 cylinder motors, and by late 1979 were on all larger motors.

CDM ignition consists of a stator, a trigger and one coil/CDI unit per cylinder. It is similar to automotive ignitions, where the coil packs are powered by battery feed and fired by pulses from the ECU. These units are newer than the ADI style.

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Ok. I didn't know that I had an ECU (Electronic Control Unit). Where is it incase it crashes and I have to fix it?

I don't know if CDM ignitions in your era had an ECU. It may be just a trigger and carbs. Newer motors will have an ECU, when they went to direct or manifold fuel injection. I just am not sure when they were incorporated.

Chris1956 said:

I don't know if CDM ignitions in your era had an ECU. It may be just a trigger and carbs. Newer motors will have an ECU, when they went to direct or manifold fuel injection. I just am not sure when they were incorporated.

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My engine like the same year 90 I had previously is just stator voltage and triggers to the modules and regular carburetors with common linkage. I had thought about maybe one day upgrading to a newer engine with fuel injection and an ECU and all that stuff......but being an old school guy.....shade tree mechanic if you will, that thought is way out there in the future......way out there.

In that case, you will need to keep your current motor running. Here at the NJ shore, 2 cycle OB engines and OB engines with carbs are just about gone. Between the salt water and the shortage of DIY mechanics, old motors are junked more frequently than those used on lakes, and where owners seem more willing to turn a wrench.

Do you have spark? Checked compression?

Texasmark said:

You didn't say if it spun up lively with the starter, just wouldn't ignite and run on its own. You need about 200 RPM min. to spin the engine fast enough for the stator to develop enough voltage to light off the plugs.

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Yes, battery is fully charged and engine spins over very quickly, I currently have all spark plugs removed the the engine spins very fast.

Chris1956 said:

Does that motor have ADI ignition or CDM ignition? In CDI ignition, the switchbox pulses voltage to the coils to fire the spark plugs. On CDM ignition, the stator powers individual CDI units at each spark plug.

Since you replaced all the likely suspects, except the trigger, you might check for voltage at the switchbox (or CDM units) from the stator.

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It has 4 individual coil packs that go to each spark plug, how do I check voltage and what should the voltage be?

Chris1956 said:

I don't know if CDM ignitions in your era had an ECU. It may be just a trigger and carbs. Newer motors will have an ECU, when they went to direct or manifold fuel injection. I just am not sure when they were incorporated.

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This one does not have an ECU, the wires go straight to each coil pack.

CLi87 said:

This one does not have an ECU, the wires go straight to each coil pack.

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ebay sells manuals for that engine. I have essentially the same 115, only a 2002 model. You covered everything that I would have suggested so I will suggest you get a manual and start rummaging through the trouble shooting section, or explanation area where they tell you how things work and compare what you read to what you have in front of you.

You don't have any mouse or rat droppings around the engine? If so, look for insulation chewed off wiring and wires touching that aren't supposed to be touching.

Go to an auto parts store and get a roll of 16 AWG wire and some alligator clips that will fit over the starting solenoid input 3/8" stud (battery + connection) and the black - wire from the battery that connects to the engine block. The battery needs to be fully charged and connected to the engine in the two spots mentioned like is the case during normal operation.

Remove the 8 pin remote control wiring harness plug from the engine compartment.

Remove the insulation from both ends of a suitable length of wire (3 each) and twist the wire on one end so that it will fit inside the sockets on that 8 pin plug and attach an alligator clip to the other end.

One wire goes in the Pin 2 (the color of the wire normally attached to Pin 2 is either Purple or Red with a Purple stripe. The alligator clip on the other end of this wire goes to the 3/8" stud on the starting solenoid where the battery red wire is connected.

The second wire is to be inserted in pin 6 identified by a yellow wire with a black stripe (don't confuse it with the black/yellow color code as that is the engine kill pin when grounded). This yel/blk wire is your fuel enhancement power.....the power you send to the engine when you are ready to start the engine and turn the key to on and PUSH in on the key. So, in operating the alligator clip on the other end of this wire, assume you are starting via the key as mentioned and touch the alligator clip to the same 12v 3/8" terminal mentioned above for as long as you normally "prime" your engine when attempting to start.

The third wire is to be inserted into Pin 7 which is identified by the yellow wire with a red stripe........this is the terminal that gets 12v when you want to start the engine so do not connect the alligator clip to anything until you are ready to attempt to start the engine.

Ensure that your fuel is hooked up and the carbs have been filled with fuel.....firm squeeze bulb on the input fuel line.

Activate the fuel enhancement for as long as you normally do, and then while keeping it activated, touch the alligator clip on wire 3 to the 3/8" stud mentioned and hold it there temporarily, which should cause the starter to start spinning.

If the engine starts or tries to start...meaning its getting fuel and ignition, then your problem is in the wiring harness to the control box or in the control box.

What you are doing here is simulating the voltage (signals) to the engine that normally come from the ignition key either on the dash or in the control box when you attempt to start your engine normally....nothing more, nothing less. The purpose is an attempt to locate the source of the problem.......with what you have changed in the engine it seems to me that the problem isn't in the engine proper.

I think my issue is the trigger assembly, I tested the brown to black and white to purple and wasn't getting any ohm reading on either pair of wires

CLi87 said:

Yes, battery is fully charged and engine spins over very quickly, I currently have all spark plugs removed the the engine spins very fast.

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Well its supposed to spin fast if working properly as there is no resistance to dissipate the energy being consumed from the battery while attempting to start. AKA no compression impeding rotation.

To get spark across the spark plug electrodes you need to ground (attach to the engine block or battery negative) the threads of the plug or metallic parts there to attached to get it to fire with the HV lead attached to the insulated terminal on top of the plug. For the high voltage lead attached to a plug and the plug being out in thin air proves nothing!!!!!

Mercury sports the philosophy that it generates 40.000 volts from its CDM packs in a few Microseconds.... 2 or 3 times 10 exponent -6 (zeroes) x one second....basically its a sharp leading edge, very fast.......but unloaded....works great to fire plugs reliably in all sorts of combustion environments...... In short nothing is connected to the output wire. You put a load on that, like a spark plug with the HV attached to the insulated terminal and the threads or case attached to the battery negative and the slope of the curve broadens widely.

Breaking that down into common sense when spark plugs usually fire off and dissipate the coil's energy at about 18, 000 you have a lot of backup for bad plugs or other ignition problems.

Brown wire to black and white????? What brown wire? In m 2002 there are no Brown wires. Tan and Tan with blue stripe are for alarm functions....over themp and low oil in the onboard oil storage tank.

Mark, Not that it matters much, but battery/coil ignitions often produce 20K volts. CDi was always much higher. An early aftermarket unit we installed on our 1970 Mercury claimed 600,000 volts. It took the battery voltage and stepped it up to 300V, and then sent it thru the ign coil.

Texasmark said:

Well its supposed to spin fast if working properly as there is no resistance to dissipate the energy being consumed from the battery while attempting to start. AKA no compression impeding rotation.

To get spark across the spark plug electrodes you need to ground (attach to the engine block or battery negative) the threads of the plug or metallic parts there to attached to get it to fire with the HV lead attached to the insulated terminal on top of the plug. For the high voltage lead attached to a plug and the plug being out in thin air proves nothing!!!!!

Mercury sports the philosophy that it generates 40.000 volts from its CDM packs in a few Microseconds.... 2 or 3 times 10 exponent -6 (zeroes) x one second....basically its a sharp leading edge, very fast.......but unloaded....works great to fire plugs reliably in all sorts of combustion environments...... In short nothing is connected to the output wire. You put a load on that, like a spark plug with the HV attached to the insulated terminal and the threads or case attached to the battery negative and the slope of the curve broadens widely.

Breaking that down into common sense when spark plugs usually fire off and dissipate the coil's energy at about 18, 000 you have a lot of backup for bad plugs or other ignition problems.

Brown wire to black and white????? What brown wire? In m 2002 there are no Brown wires. Tan and Tan with blue stripe are for alarm functions....over themp and low oil in the onboard oil storage tank.

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The wires from the trigger assembly? I was told to check ohms from black to brown and white to purple to make sure the trigger assembly is good.

CLi87 said:

The wires from the trigger assembly? I was told to check ohms from black to brown and white to purple to make sure the trigger assembly is good.

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Get a manual. Then you have reliable access to the whole engine and you can troubleshoot with confidence, not hit and miss guessing or possible errors from people like me!

Excellent advice Texasmark.