Johnson 50ESL72C Starter Problem

[Nathan Hamilton]

I am in the process of building a boat and acquired a 1972 Johnson 50HP motor. The motor has been installed and was working properly. I had to use this technique to replace a faulty shift switch: http://forums.iboats.com/showthread.php?t=175907 , and it worked perfectly. However, after working on some other parts of the boat, I came back and tried to run the motor. Now, inserting the key and attempting to start does nothing at all.

I have followed these troubleshooting instructions: http://continuouswave.com/whaler/reference/electricStart.html . The motor passed the first test but failed the sixth. The guide suggests that this is a solenoid failure, but I don't see any reason why the solenoid would have failed since the last motor test (it's only been a week since it ran properly).

My guess is that the ignition switch might've failed based on a problem I had a couple of times when testing the motor earlier. The motor failed to turn off a couple of times upon turning the switch to the "Off" position and removing the key.

Is there a test I can perform to verify whether or not the switch is the problem, or am I going down the wrong path?

 

[Daviet]

Re: Johnson 50ESL72C Starter Problem

So you have voltage at #3 when you turn the key to start.
You notice #2 goes to ground #1, if the solenoid is not clicking and passing voltage it is defective. The solenoid is an electrical componet and go bad at any time.

 

[oldrudedude]

Re: Johnson 50ESL72C Starter Problem

Check the safety switch. It is located just behind the pivot bolt of the throttle lever on the starboard side of the motor. It's purpose it to prevent you from starting the motor with too much throttle. It grounds the primary circuit of the starter solenoid. A quick test would be to ground the solenoid primary by bypassing the switch.

If the engine does not turn off the blocking diode is toast. Is your shift control push-button or three-way toggle activated by the helm throttle lever?

 

[Nathan Hamilton]

Re: Johnson 50ESL72C Starter Problem

Yes, #3 shows full battery voltage when the key is turned.

The information about the safety switch is interesting because I have adjusted the throttle since the last time I ran the motor. Does "grounding the solenoid primary" involve connecting the lead to the safety switch, #3 to #2?

My remote uses the three-way shift switch.

 

[oldrudedude]

Re: Johnson 50ESL72C Starter Problem

Run a jumper from ground to the lead on the safety switch.

 

[oldrudedude]

Re: Johnson 50ESL72C Starter Problem

Ok, now I see where the confusion comes from. The diagram on the continuous wave site does not reflect the way your engine is wired. They have the power going from the ignition switch through the safety switch to the solenoid, then straight to ground. However, your engine is wired differently:

On your engine the power runs from the ignition switch directly to the starter solenoid. Your starter grounds by going through the safety switch. Different setup but same effect. So to bypass the safety switch you simply have to ground out the lead on the safety switch this will ground the solenoid. To varify this you will notice that there is only one lead on the safety switch. Correct?

 

[oldrudedude]

Re: Johnson 50ESL72C Starter Problem

If you use the CW diagram and you have power at #3 but not at #2, the primary circuit of the solenoid is fried or the connections on the solenoid have to be cleaned. If you have power at #3 AND #2, look at the safety switch.

 

[Nathan Hamilton]

Re: Johnson 50ESL72C Starter Problem

Yes, the safety switch has only one lead.

Voltage measurements with the key turned to start show battery voltage at both #2 and #3 and voltage at the starter (#8) is near zero before bypassing the safety switch. After bypassing the switch as per your instructions, voltage on #2 and #3 both read zero. However, the solenoid does now click and a voltage measurement at the starter reads proper battery voltage. I'm assuming that this means success!

So, now that the safety switch has proven to be the culprit, what do I do? Should wiggling the throttle "reset" the safety switch to its working state? I don't understand how the safety switch monitors the throttle position. I assume that for safety's sake, I should not just permanently bypass the safety switch.

Thank you very much for your help.

 

[Daviet]

Re: Johnson 50ESL72C Starter Problem

I would replace the safty switch, not bypass it.

 

[oldrudedude]

Re: Johnson 50ESL72C Starter Problem

Back off on the throttle. The throttle arm has a cam on it that pushes in a button on the safety switch. As the throttle arm advances the button is pushed in more. When the throttle is advanced to the point where starting the engine may prove hazardous to the engine, the safety switch discontinues the ground of the primary solenoid circuit. This makes you unable to start your engine by breaking the ground of the primary solenoid circuit. If you have advanced the throttle too far the safety switch prevents you from over-revving your engine.

The solenoid should not only click, it should turn the starter. Is your battery low on charge?

Bypassing the safety switch should have allowed the starter to turn over the motor. It was a test to determine why the solenoid is not clicking. The circuit you have been testing is just a low current circuit through an electromagnet in the solenoid. The electromagnet moves a bar of metal in the solenoid, bridging two contacts, and allowing the big juice to turn the starter. At this point all you have determined is: The safety switch was preventing you from starting the motor.

You mentioned that you had adjusted the throttle. Perhaps you adjusted it too far forward. Try adjusting it back to see if that makes the solenoid click. If if does, the safety switch was just doing its job. Hoorah for the safety switch.

If the solenoid now clicks but does not turn the starter, your battery is almost dead, the solenoid is malfunctioning, or you have some high resistance (could be corrosion at the contact points) in the starter system. Ensure All the contact points are clean and shiny (clean them with medium sand paper and put them back together) between the battery and the starter ( this means all the contacts you have just tested as well as the heavy cables that connect the battery, through the solenoid to the starter).

The safety switch is probably not the problem.

 

[Nathan Hamilton]

Re: Johnson 50ESL72C Starter Problem

I will try adjusting the throttle position this evening to see if it corrects the safety switch. The starter is not engaging because I removed its lead for safer testing. I will be testing it this evening with the starter lead reattached.

 

[oldrudedude]

Re: Johnson 50ESL72C Starter Problem

I will try adjusting the throttle position this evening to see if it corrects the safety switch. The starter is not engaging because I removed its lead for safer testing. I will be testing it this evening with the starter lead reattached.

Good stuff. Let us know how it turns out.

 

[Nathan Hamilton]

Re: Johnson 50ESL72C Starter Problem

Adjusting the throttle position solved the issue with starting the motor. It now starts properly without bypassing the safety switch (provided that the throttle remains in the proper position).

With this issue out of the way, I moved on to doing something about the motor not turning off. I purchased a new diode and replaced the original. However, when I ran the engine earlier this evening, it again failed to turn off. Excepting the fact that the new diode might be defective, does anyone have any suggestions for further troubleshooting this issue? I do plan to test both the new and old diodes using a guide in the Seloc manual for this motor to see if that sheds any light on the problem. Is there any chance the ignition switch might be at fault?