Yanmar 2GM20 won't start when sensors wire connected to Key switch.

[cat ballou]

I hope someone might know the answer to this problem.

The engine would not start as long as the sensors wire is still connected to the back of the Key switch terminal.

It will start normally (key ON) with the Push button if I disconnect the sensors wire or if I touch the Push button wire to the Hot terminal in back of the Key switch with the key off.

Any help will be appreciated.

Ron

[NoTies]

So, with the "sensor" wire connected will it crank and not start or not crank at all?

[kmacdonald]

Is it the start in neutral or out of gear switch?

[cat ballou]

Thank you for responding.

When the sensors wire is connected to the back of the key switch terminal, the key turned to the 'On' position and the 'Push Button' is pushed, nothing happens, not even a click.

I always start in 'neutral'.

[Wotname]

Hmm... more detail please. What Yanmar panel do you have? Is this a sail drive?

Most 2GM20s don't have any "sensors" wire on the back of the key switch but apparently your does so...

Do you know where the sensor wire goes?
What is the colour code?
When did the fault occur?
Any other information that might help?
Pictures?

[Wotname]

Typical 2GM20 panel wiring with type B panel - note, no sensor wire on key switch which means yours is different!

[NoTies]

If your trouble shooting skills with a voltmeter aren't too good I would firstly check the smaller red wire coming from the large post on the starter motor. Make sure it's clean and tight. Next, open up the plastic fuse case located on the harness above the starter somewhere from memory. Check to see the spring steel connections for the fuse at either end are clean and tight. Next check would be the multi plug connector that hooks into the harness extension back to the panel. Separate the plugs and check for corrosion, spray some water dispersant and slide the plug in and out of the socket a few times to clean. There is from memory a separate wire beside the multi plug which is the signal wire for the starter, carefully separate and clean this (just because you can, it is unlikely to be the fault). Finally check all connections at the panel. It sounds to me like you have a voltage drop somewhere on the main power feed from the engine to the panel.

[cat ballou]

Wotname; The control panel is the 'B' type. What i called 'Sensor wire' is also activating the Tachometer (and Oil pressure alarm). It's red with a black line on it.
i do have a sail drive and the engine is a 2gm20 FC. from the year 2000.

Starting with the push button started being 'sketchy' about a month ago and got worse to the point where now it wouldn't start at all unless i disconnect that wire from the back of the key switch terminal but then I don't have the Tachometer running or the Low oil pressure warning.

[cat ballou]

Thanks NoTies, I'll get that spray and try that. It does behave like there is a bad contact someplace. Just need to find where that is.

[Wotname]

Originally Posted by cat ballou

Wotname; The control panel is the 'B' type. What i called 'Sensor wire' is also activating the Tachometer (and Oil pressure alarm). It's red with a black line on it.
i do have a sail drive and the engine is a 2gm20 FC. from the year 2000.

Starting with the push button started being 'sketchy' about a month ago and got worse to the point where now it wouldn't start at all unless i disconnect that wire from the back of the key switch terminal but then I don't have the Tachometer running or the Low oil pressure warning.

OK, that makes sense now!
No Ties (post #7) is very good advice and if that doesn't sort your problem, then try shorting out the key switch (not the start switch) - terminal 30 to terminal AC on the drawing posted earlier. If it works now then your key switch is faulty (high resistance).

However if the above doesn't resolve the issue, I would try running a temporary wire direct from 12+ve terminal on the battery direct to the terminal AC on the key switch. If this temporary wire works, then you have to go back to post 7 and recheck as the fault is somewhere in the fuse, harness, connectors or key switch.

[cat ballou]

Thank you Wotname.