1995 115 4 cylinder-No fire when blk/yellow wire connected to switch box

[1nebel0]

I have a real challenge and need some outside advice...very knowledgeable with the electrical system on Merc's as I have many diferent h.p. motors but never a problem like this...When the blk/yel wire is hooked to the switch box no spark..disconnect it and spark on all cylinders...I checked the wire with my ohm meter to ground and it doesn;t show continunity so don't have a bad wire/plug. From all that I have read nobody talks about a bad switch box, or stator but just a bad ignition switch/circuit. I used a CDI remote starter box to eliminate controller/key switch Any ideas are gladly welcomed...

 

[Texasmark]

Re: 1995 115 4 cylinder-No fire when blk/yellow wire connected to switch box

You have identified your problem. That wire is normally grounded in the remote control when the ignition switch is turned to the off position. It grounds out the triggers of the CDIs to kill the engine. You have proven that the source (remote control or connections) is the problem so investigate the source more thoroughly. Was the switch in the off position when you did the ohm check?

If worse comes to worse, go back to the engine and find the test plug which has a rubber plug in the end of a black/yel striped wire segment which you can remove and test for your short circuit with all the wiring connected.

Possibly the switch is worn, or some metallic particles have worn off and made a trail between off and on terminals. Wiggle the wiring and see if that changes anything. Is something rubbing in the switch box whereby the insulation is worn off the wire and something metallic is touching the conductor outside the remote; inside?

I'd like to know the outcome from your effort.

HTH,

Mark

 

[Faztbullet]

Re: 1995 115 4 cylinder-No fire when blk/yellow wire connected to switch box

If you used the CDI remote box to test, you eliminated any problem in harness to remote,key and kill circuit.It appears the problem is in the internal wiring harness so remove factory tape behind female cannon plug and check to see if wire is damaged in some fashion.

 

[CharlieB]

Re: 1995 115 4 cylinder-No fire when blk/yellow wire connected to switch box

Exactly which connectors did you unplug to test?

The black/yellow between the switchbox and the motor harness, the main cannon plug, Blk/Y at the control box lanyard switch, or at the Ignition switch?

Somewhere along this line, and it could be anywhere, you have a ground. It could be at any point where a wire 'flex's' the wires can break and 'porcupine' poking a strand out of the insulation to ground.

Also, double check your meter, turn the 'scale' up, it does not take a real good ground, a self-ranging digital often will show a weak ground where the analog set on X 1 or X 10 will barely move.

 

[1nebel0]

Re: 1995 115 4 cylinder-No fire when blk/yellow wire connected to switch box

Thanks guys...As Faztbullet stated I am using the CDI unit which takes the controller out of the picture. I tested both the end that goes to the switch box to ground and the pin from the plug end to ground and no continunity... I am using the Merc Digital meter-auto ranging...when I touch the two together they immedately go to zero or continunity...The wires are not taped to the plug as all wires are exposed unlike my other Merc's that have tons of factory tape...CharlieB not sure I understand your last paragraph in regards to the digital meter....If the wire is shorted, I should see zero on the meter correct? While writing this I came up with an idea... I will make up a new wire, hook it to the switch box and not strip the other end so no wire exposed.. This would simulate like it was sitting in the cannon plug....If it continues to spark...bad wire...if no spark, pull my remaining hair out...stay tuned for this one!!!

 

[Texasmark]

Re: 1995 115 4 cylinder-No fire when blk/yellow wire connected to switch box

Thanks guys...As Faztbullet stated I am using the CDI unit which takes the controller out of the picture. I tested both the end that goes to the switch box to ground and the pin from the plug end to ground and no continunity... I am using the Merc Digital meter-auto ranging...when I touch the two together they immedately go to zero or continunity...The wires are not taped to the plug as all wires are exposed unlike my other Merc's that have tons of factory tape...CharlieB not sure I understand your last paragraph in regards to the digital meter....If the wire is shorted, I should see zero on the meter correct? While writing this I came up with an idea... I will make up a new wire, hook it to the switch box and not strip the other end so no wire exposed.. This would simulate like it was sitting in the cannon plug....If it continues to spark...bad wire...if no spark, pull my remaining hair out...stay tuned for this one!!!

Yes on following up. like your idea on the separate wire. On ohms, the leads are somewhere around 0.3-.4 ohms plus the wiring resistance of any wiring and r depends upon gauge. You could probably measure back into your CDI's to see what their input resistance is. I don't have the schematic, but assume a resistive voltage divider is there where the trigger comes in and goes to the SCR switch. Grounding the black/yel apparently drops the voltage to a value that will not fire the SCR which dumps your capacitor charge and generates ignition.

Soooo if that input resistance (of the CDI) to ground is 100 ohms or so, applying ground to ground out the triggers could be 10-50....more-less ohms above battery - potential and still get the job done....killing your triggers. If the CDI input resistance is 1k to gnd it could be as high as 100-200 ohms and still kill them.

HTH
Mark

 

[Faztbullet]

Re: 1995 115 4 cylinder-No fire when blk/yellow wire connected to switch box

Grounding the black/yel apparently drops the voltage to a value that will not fire the SCR which dumps your capacitor charge and generates ignition.

On a model with switchbox, the black/yellow actually grounds out the stator input to internal rectifier...


On a CDM ignition system it shorts the CDM internal capacitor to ground so it cannot discharge..

 

[Barnacle_Bill]

Re: 1995 115 4 cylinder-No fire when blk/yellow wire connected to switch box

According to the schematic there should be 2 black yellow wires going to the switch box. One goes thru the harness to the switch and the other goes to the rev limiter. Try unplugging it at the rev limiter and see if spark is there.

 

[jeffersondodson561]

Re: 1995 115 4 cylinder-No fire when blk/yellow wire connected to switch box

Disconnect the boat wiring harness [cannon plug] and crank the engine over with a remote starter Autozone? (was just in 2nd HF this week did not see the remote starter in that store either don't know how to take that) and if the engine has spark your problem is on the boat side if it still does not have spark problem is on the engine side. Just remember you will to ground out the black/yellow wire manually to stop the engine if plugs are left in

 

[1nebel0]

Re: 1995 115 4 cylinder-No fire when blk/yellow wire connected to switch box

Good catch bhile as I was hoping it was the rev limiter that was bad..when I hook it up alone, I still have spark. I can then take it off and hook up the other black/yellow wire and no spark..It is so darn cold here in the valley when I get home I will do the single wire test this weekend...This was has me stumped...Plain and simple, if the wire I make up let's it have spark, it will be a bad blk/yellow wire and easy fix. If there is no spark there goes the rest of the silver hair..........Steve

 

[Texasmark]

Re: 1995 115 4 cylinder-No fire when blk/yellow wire connected to switch box

According to the schematic there should be 2 black yellow wires going to the switch box. One goes thru the harness to the switch and the other goes to the rev limiter. Try unplugging it at the rev limiter and see if spark is there.

That's apparently the one I referred to as having the rubber plug and being an open ended wire. I don't have a rev limiter on my engine but apparently the harness is shared with models having one which explains the presence of this second wire.

Mark

 

[Texasmark]

Re: 1995 115 4 cylinder-No fire when blk/yellow wire connected to switch box

Good catch bhile as I was hoping it was the rev limiter that was bad..when I hook it up alone, I still have spark. I can then take it off and hook up the other black/yellow wire and no spark..It is so darn cold here in the valley when I get home I will do the single wire test this weekend...This was has me stumped...Plain and simple, if the wire I make up let's it have spark, it will be a bad blk/yellow wire and easy fix. If there is no spark there goes the rest of the silver hair..........Steve

I have no idea as to what is contained in the rev limiter. I do know that it will limit rpm's and probably does it by messing with triggers. If it has malfunctioned it may "mess with the triggers" constantly. My engine doesn't have a limiter and engines were built for many years without them so if you have one try, as you say to run without it before you run the separate wire.

HTH,

Mark

 

[1nebel0]

Re: 1995 115 4 cylinder-No fire when blk/yellow wire connected to switch box

Thanks to all... will let all know what the test results are...this is very frustrating......