1988 Johnson 4hp Deluxe - suddenly no spark (Update)

[Moody Blue]

Have been working on this new-to-me motor hoping to be able to use it as a trolling motor.

Replaced water pump impeller, changed LU oil, replaced ignition sensor module under flywheel that was physically broken.

I also repaired the kill switch wire that runs from the tiller handle to the 5-pin connector that connects to the ignition module. When I bought the motor, the kill switch wire was pulled out of the 5-pin connector and laying loose. I had the motor running today and used the kill button on the end of the tiller handle to stop the motor. Now there is no spark at all at either cyl.

I checked the kill circuit and found it worked as expected. With the tether in place on the kill switch, I measure open circuit on the kill wire. With the tether removed from the kill switch, I measure a short to ground on the kill wire.

Sure would appreciate some advice on what to do next.

 

[Moody Blue]

Re: 1988 Johnson 4hp Deluxe - suddenly no spark (Update)

OK, I went and pulled the kill wire from the tiller out of the 5 -pin connector to the ignition module. Engine started right away and ran fine. Thank goodness for that. Now onto the problem.

I double/triple/quadruple checked that the kill wire is open circuit with the lanyard attached. Absolutely 100% certain. Remove the lanyard and kill switch shorts to gnd. I'm assuming that's how it is supposed to work.

Next I measured voltage between the ignition module kill wire (BLK/YEL) and gnd and measured about 525Vac using a DVM. I only decided to measure it after I got one hell of a shock while rigging up a test wire. SHould that wire be energized, or is there a problem perhaps in the wire harness?

Once the motor is running I connected the kill wire ( I KNOW it is open circuit) from the tiller to the 5-pin connector to the ignition module and the motor dies. What is going on?

THoughts, ideas, suggestions ?

 

[boobie]

Re: 1988 Johnson 4hp Deluxe - suddenly no spark (Update)

Without seeing it, it sounds like a prob with your kill sw wires shorting to grd some where.

 

[Haffiman]

Re: 1988 Johnson 4hp Deluxe - suddenly no spark (Update)

The voltage in the stop circuit might create quite some issues that might not be detected by ohm testing the stop switch.
Do the following:
Remove the ground lead from ground in the kill wire system, keep the other lead attached to the power pack. Start the engine and measure voltage at the ground end of the kill wiring. It may not be the 525 you measured earlier, but simply 50 is enough to trigger the stop function. Seen a lot of stop switches with minor leaks causing similar problems.

 

[Moody Blue]

Re: 1988 Johnson 4hp Deluxe - suddenly no spark (Update)

Will try that tomorrow.

Kill switch was working but acting up when I first tried to start the motor. I installed the lanyard but motor would not start. Checked for spark and none. I pulled out kill button further by hand and got spark so I made a simple spacer that fit between the lanyard clip and kill button. Motor started fine and quit when I removed the lanyard as expected. Tried this several times without issue. I then started the motor with lanyard/spacer installed and then PRESSED in the stop button. Motor quit as was expected. Tried to restart but no spark.

 

[Moody Blue]

Re: 1988 Johnson 4hp Deluxe - suddenly no spark (Update)

Without seeing it, it sounds like a prob with your kill sw wires shorting to grd some where.

Using an ohm meter I can say with absolute certainty that the kill circuit is OPEN circuit with the lanyard installed. The presence of high voltage surprised me. Will do further tests tomorrow.

 

[kodibass]

Re: 1988 Johnson 4hp Deluxe - suddenly no spark (Update)

When you ground the kill switch wire to the block insure it is grounded alone to the block, no other wires sharing the ground bolt with this wire, I just went thru this with a 55 jonny, I'm not sure why but on this motor the ground from the kill switch had to be grounded to the block and away fro the coil & pwrpak grounds to work properly? good luck

 

[Haffiman]

Re: 1988 Johnson 4hp Deluxe - suddenly no spark (Update)

When you ground the kill switch wire to the block insure it is grounded alone to the block, no other wires sharing the ground bolt with this wire, I just went thru this with a 55 jonny, I'm not sure why but on this motor the ground from the kill switch had to be grounded to the block and away fro the coil & pwrpak grounds to work properly? good luck

All electronics must have 'clean' ground', meaning no other sharing cables to the point. In this case you have about 250 Vac running which you do not want to 'reverse' into the PP or coil for any reason. Even if the current originally comes from the PP it may blow the internals when going through the backdoor.

 

[Moody Blue]

Re: 1988 Johnson 4hp Deluxe - suddenly no spark (Update)

Interesting comments on the grounding. There are three "GND" connections/wires and only two connection points that I can figure.

GND lead from kill switch, GND lead from ignition module and a jumper wire with terminals at each end. Presently the ignition module GND and one end of jumper are connected at the engine block, and the kill switch GND lead and other end of jumper are connected to the engine cowling via the bolt that holds down the ignition module.

 

[Haffiman]

Re: 1988 Johnson 4hp Deluxe - suddenly no spark (Update)

As long as the ground connections are 100% clean it will not be any problems and 'back-feed'. However after some time the ground screws have a bad habit of corroding, you get a whitish oxidation powder on the threads that insulates, and the back-feeding starts!! Loss of proper ground is the most common reason for failures of power packs. It might be the pack-ground itself, it might be a failed spark-plug (which is a ground connection) that sends the spark 'wrong' way. When OMC released their lates 'big-bore' 9,9/15 they made the mistake of grounding the pack on the lower screw which very soon got corrosion(due to water mist/spray) and ground problem. Result: Pack failed. After a couple of years they learned their mistake, moved the ground to upper screw and no more pack problem!! They did a lot of funny grounding during their days that unnecessary ruined a lot of packs and electronics.

 

[Moody Blue]

Re: 1988 Johnson 4hp Deluxe - suddenly no spark (Update)

Didn't get a chance to work on the motor today but the terminals themselves are very clean. Didn't notice the condition of the threads but I did make sure to install star type lock washers under all terminals to be sure of a good connection.

I will be sure to double check all connections.