Yanmar Starting Issue – Ignition Switch Problem

[s/v Jedi]

All the posted advice is good but let me add the best way to measure voltage drop:

Set the multimeter to Volts, so that 0-15 V can be measured. Now, to test voltage drop between battery and ignition switch, put one lead (doesn’t matter which one) on the battery positive and the other on the ignition switch. The meter will show the voltage drop. This also works for negative wiring: hold one probe to the bolt kn the engine that has the negative cable and the other probe to the battery negative terminal.

The voltage drop is the current in amps multiplied by the resistance in Ohms. If you switch the meter to Ohms and measure the circuit resistance, then you can simply calculate the current: divide measured voltage drop by measured resistance

[taylormobile]

I had the same problem with our 1989 Yanmar. In fact the PO had installed a backup ignition switch near the engine. After much research I found that the Yanmar wiring harness is undersized. I ran a new wire which helped but I still had inconsistent results. The best solution that I found is to add a start relay in the engine area to shorten the path of the high amperage circuit. I was told that all newer Yanmar harnesses have this relay. I added the relay 4 years ago and the problem has never reoccurred. However, at the same time 4 years ago I also installed a new start solenoid. So I actually had 2 variables with the fix.

Steve
1989 Catalina 42

[Cpt Mark]

Or... it could be that your neutral cutoff switch is malfunctioning.

[Bycrick]

When troubleshooting this kind of problem, I’d suggest that a digital voltmeter is a poor tool. It has such a high input impedance that it is, by design, completely insensitive to any resistance in the measured circuit.

If you had a piece of 2/0 battery cable, which normally has about 2000 wire strands, if only one of the strands was good, you’d still read the correct voltage.

In many cases like this, you’re far better off troubleshooting with an old-fashioned incandescent light bulb tester. With them, a high resistance connection will show up much faster.

[zengirl]

I don't know if this will help. I have a Yanmar 3YM30. I freaked one day when it wouldn't start. There was no reason for this. I started messing around with the starter button and found that when I pressed in the middle it wouldn't start, when I put the pressure on the left side of button it started every time.

[Stu Jackson]

Originally Posted by taylormobile

>>>>>>>>>>>>> After much research I found that the Yanmar wiring harness is undersized. I ran a new wire which helped but I still had inconsistent results. The best solution that I found is to add a start relay in the engine area to shorten the path of the high amperage circuit. I was told that all newer Yanmar harnesses have this relay. I added the relay 4 years ago and the problem has never reoccurred. >>>>>>>>>>>>>>>>>>>

Steve's right. Between the harness wire size, the harness trailer plug connectors and the distances involved, Steve's recommendation makes sense.


Why? 'Cuz tons of Yanmar owners have done it. And they repeatedly bring it up on sbo.com on a regular basis. I think there may be more small Yanmar owners there, since this forum has a much wider vasriety of engines.


https://forums.sailboatowners.com/in...yanmar%20relay

[Howler]

Had the same problem with a Yanmar 3G30F. The distance between the ignition button and the starter motor was causing a drop in power delivered to the starter motor. As others, a relay installed on that circuit did the trick.

[oilystain]

Strangley enough, the same thing happened to my yanmar this spring. The buzzer didn't come on when i threw the ignition switch and the engine made no effort to start. The buzzer was fixed by replacing the panel fuze and the no start issue was solved with a new start button. Probably not what is going on with your engine but that's what happened to me.

[wingssail]

I guess that many of us have had this problem with our Yanmars. In my case the first thing I do was touch a jumper wire from the battery to the small terminal on the starter solenoid. The engine ALWAYS leaps to life. OK the starter and battery are OK. If not you know where to focus.

Next I run a temporary wire from the battery to the engine panel where the heavy red line goes (check the wiring diagram). Usually this solves the problem.

If not, then you can touch the temporary line to the white wire (check the wiring diagram) which goes to the solenoid. (this bypasses the switch) however, I've always found that the either the red wire or the white wire have a bad connection at the plug. I've fixed the problem more than once over the many years, and it's always been that.

BTW, a low battery exacerbates the problem.

[wesevans]

Had a similar issue years ago turned out to be neutral lock out. Cycled the shift lever and problem solved.

[Wotname]

Originally Posted by taylormobile

I had the same problem with our 1989 Yanmar. In fact the PO had installed a backup ignition switch near the engine. After much research I found that the Yanmar wiring harness is undersized. I ran a new wire which helped but I still had inconsistent results. The best solution that I found is to add a start relay in the engine area to shorten the path of the high amperage circuit. I was told that all newer Yanmar harnesses have this relay. I added the relay 4 years ago and the problem has never reoccurred. However, at the same time 4 years ago I also installed a new start solenoid. So I actually had 2 variables with the fix.

Steve
1989 Catalina 42

Originally Posted by Stu Jackson

Steve's right. Between the harness wire size, the harness trailer plug connectors and the distances involved, Steve's recommendation makes sense.


Why? 'Cuz tons of Yanmar owners have done it. And they repeatedly bring it up on sbo.com on a regular basis. I think there may be more small Yanmar owners there, since this forum has a much wider vasriety of engines.


https://forums.sailboatowners.com/in...yanmar%20relay

Originally Posted by Howler

Had the same problem with a Yanmar 3G30F. The distance between the ignition button and the starter motor was causing a drop in power delivered to the starter motor. As others, a relay installed on that circuit did the trick.

Originally Posted by Cpt Mark

Or... it could be that your neutral cutoff switch is malfunctioning.

The above posts (and others similar) no doubt fixed the problems each poster experienced themselves however a careful reading of the OP indicates the OP has a slightly different issue. Of course, the OP may be in error in the fault description but until he confirms any error, I prefer to take the fault description as factual.

The OP stated:

"The primary symptom is that the engine does nothing when the ignition switch is switched to on and the start button is depressed. Gordon said that normally the panel will buzz when the ignition is on but the engine is not running. The panel is not buzzing at all. "

Now re-read the emphasised sentences.

There are only two credible scenarios that account for the fault description. Either insufficient battery +ve volts at the Key Switch OR additional (and concurrent) faults in the buzzer / idiot light low oil pressure circuit as well as faults in the start circuit.

The OP then detailed some of the voltage readings which supports the view there was a loss of voltage at the Key Switch. No amount of additional relays or heavier wiring in the start circuit will fix faults in the Key Switch and/or buzzer circuit.

First rule of troubleshooting - check the most probable culprit first before looking at the less likely. In this case, this means confirming there is sufficient voltage (i.e. >12.5V) at the Key Switch when it is ON. If there are good volts at the Key Switch and if the fault description hasn't changed, then proceed to investigate the start circuit AND the Buzzer circuit as there will be two or more separate faults.

Another approach that has some merit is to put away the meters, test lamps, schematics etc, sit down with a plate of snacks and drinks and simply (and slowly) disassemble EVERY terminal and interconnect plug, inspect, clean or replace as required and then re-assemble. Begin at the batteries poles, move along to the master switch(s) then the engine and finally the panel. There is a fair chance the problem will be fixed.

I prefer the diagnostic approach rather than the shotgun method but YMMV.

[Homer Shannon]

Solved!

The solution to a problem is often obvious once you’ve solved it. That is the case with this problem.

I was down at the club sorting out a couple of minor problems on my own boat when Gordon called and said that he was coming down at about four o’clock bringing a well-charged G24 battery, jumpers and some 10G wire. Would I be willing to give him a hand? I said of course and we went to his boat and set to work.

First we checked the battery he brought – 12.5 volts. Plenty enough to start a boat. We jumped the battery to the starting battery and checked the voltage again. It dropped to about 12.4 volts, but still more than enough. After connecting the battery, but before turning on the ignition, we checked the voltage on the incoming wire of the switch – 12.2 volts. We grinned at each other and said, “I think this is going to work”. Gordon turned on the key and buzzer sounded. He then punched the starter button – nothing. He turned the key off and on again – no buzzer. I checked the voltage on the incoming wire – 0.00 volts. WTF, we thought. I told Gordon, “It’s time to start checking every step of the run from the circuit breaker at the alternator all the way back to this switch. Something in here is messed up.”

I climbed down into the huge port locker of this boat, which has good access to the motor and the whole wiring run, and started checking: Alternator circuit breaker – 12.4v, solenoid - 12.4v, hot side of the in-line fuse - 12.4v, no wait, 0.00v, no 12.4v. “OK, Gordon, we have something weird going on with this fuse. The voltage is not consistent.” I asked Gordon for a pair of needle nose pliers so that I could pinch the fuse holder contacts a bit. This did not seem to help, the voltage readings were still inconsistent. I then took the fuse holder apart and the problem presented itself. The fuse, which was not blown, was defective. Both metal caps were separated from the glass cylinder. The fuse intermittently passed voltage, but it was not stable. This confirmed something I thought we saw way back at the beginning, that the voltage at the switch was 0.00 or very low. Later we got more normal readings and I had decided that those early reading were a testing error. I replaced the fuse with the spare that is in the case. Gordon turned on the switch and the buzzer sounded – loudly. After checking that my hands and feet were in safe locations, he hit the starter button and the engine fired right up.

So the whole problem was just a crappy fuse. Gordon had maintained all along that the boat had the symptoms of blown fuse but could not find any other fuses in the run and this one looked good. He was just about right, but the looks of a fuse don’t count. These bus fuses do occasionally fail and they have to be replaced. And that’s what it was.

Thanks for all you help. Your information gave us the confidence to go hard at this and solve the problem.

[Wotname]

Well done Hommer, put a another notch on the side of your meter.

This a great demonstration of the value of a patient and persistent application of trouble shooting principles. Understanding Ohm law, understanding the schematic and understanding the voltmeter will always win the day.

I am sure many readers will benefit from your experience.
The clarity of your posts is commendable.

[bailsout]

Begin with a fully charged battery. If that little screeching alarm doesn’t come on with the ignition on you won’t get anywhere. Is there an electric fuel pump?

[Homer Shannon]

Wotname; thank you for your comments. I was going to respond in a private message, but I think some of the things I want to say could be valuable for all posters, so I’m commenting publicly.

I’m fortunate to have good writing skills, which date back many, many years. I have published articles in several magazines, including Good Old Boat, and I keep a blog (not frequently updated) on my webpage, www.anythingbutawedding.com. I like to write. I started web posting back around 1993, when the web was young and I had a Merkur Scorpio car. Those were strange, alien machines and that forum was hugely useful. That experience taught me the value of web forums and I rely on half a dozen of them now.

Writing out a carefully considered post has a number of benefits. BTW, I frequently write my posts using Microsoft Word and then copy them to the forum once they are done. It is a lot easier to compose a complex post in a text editor than in the forum response field directly. Sometimes I’ll write up a post and not publish it right away. You know what they say about sleeping on a problem – it’s true for problems and for writing. Anything written can be improved by re-reading it and editing it a few hours or days later.

The first benefit to a carefully crafted post is that the quality of the responses improves dramatically with a clear description of the problem and an explanation of what part of the problem you don’t understand. If you provide your forum with a good question, you’ll likely get good, useful answers. So, I take the time to describe my situations as best I can.

The second benefit is a bit more subtle. Carefully writing out a description of your issue and describing what you know and what you don’t know clarifies your process of resolving the problem. Did you check the voltage on that post? Was the voltage 0.00 or 0.01? Am I sure? The writing process forces you to confirm what you know and will reveal facts that you may not have checked or are uncertain of. This may or may not be useful in your post, but it provides a list of items that you need to do as you proceed with your investigation.

Finally, a thorough posting WITH A RESOLUTION becomes a lasting document that other people can search and find - and will find very helpful. Having been using web forums for so long, over twenty years for boats alone, I get a laugh out of finding my own old posts while searching for information before starting a new post on some situation I’m working. There’s the problem. There’s the solution. All spelled out.

And then, there is one more thing. People like you and Compass790, a63pilot and many other are friends. You communicate well and are thoughtful in your responses. You’re not only intelligent and accurate in your knowledge, but you are pleasing to hear from. I look forward to your responses.

So, I am very grateful for your help. Many thanks to you and all the posters who have responded. And, I hope that someday, down the line, someone will read this post and say, “Aw, Christ! It’s just the bloody fuse!”