Ignition Problem on Yanmar

[JSurr]

Ahoy All, I have a Yanmar 4JH-HTB that I am having a peculiar problem with. When I turn the ignition key on both DC Bus shutdown and the engine does not crank. The engine does not turn over, the idiot lights and horns are disabled. Everything is that is running off of DC is shut down while the key is energized.
My first thought was low voltage however,
13.4 volts at the Battery
12.9 volts at Battery selector
12.3 volts at ignition switch
12.3 volts at the starter solenoid

I've had bad starters in the past and none ever shut down the DC Bus. Has anybody ever ran into something like this? What was the fix?

Thanx

[Stu Jackson]

Have you removed any trailer plug connections in the wiring harness?

[JSurr]

I have. If your referring to the two connectors just before the starter, I pulled both and cleaned them with electrical contact cleaner. I had an issue with them a while back with the RPM indicator. A couple of squirts with contact cleaner and worked fine ever since.

[NYSail]

Have you removed and cleaned your ground connection on the engine block? Lots of nasty stuff accumulates between those connectors over time

Greg

[transmitterdan]

Yes, ground connection is the most likely cause. Most people look hard at the positive connections and forget completely about the ground connections. But both positive and ground are needed and they have to handle the same current so equally important.

The tell-tale is that the voltage doesn’t drop too much but all the electrical system dies. That’s usually a sign of a bad ground somewhere.

[a64pilot]

Does the starter solenoid click?

[Howler]

Had a similar problem on a Yanmar 3G30F. Turned out the length of the wire loop to the ignition button and back to the starter motor was causing a drop in electrical power so that it wouldn’t turn the starter motor. We put in a relay. Problem solved.

[DeepFrz]

"Shuts down the DC bus". Do you mean all DC to the whole boat?

[a64pilot]

Originally Posted by Howler

Had a similar problem on a Yanmar 3G30F. Turned out the length of the wire loop to the ignition button and back to the starter motor was causing a drop in electrical power so that it wouldn’t turn the starter motor. We put in a relay. Problem solved.

That is why I asked if it activated the starter solenoid or not.
I had the same problem with my then 30 yr old wiring harness and after reading about the fix here, installed a 30 amp common automotive relay.

[Yellowjacket]

Had the same problem with a 4JH-DTE. "It's a ground," said old salt without even looking. I disagreed, spent half a day up and down, looking for bad connections, finally cleaned ground on starter, engine block, electrical bus and panel. Engine started without a hitch. Same fix for a tachometer issue.

[Stu Jackson]

Originally Posted by Yellowjacket

Had the same problem with a 4JH-DTE. "It's a ground," said old salt without even looking. I disagreed, spent half a day up and down, looking for bad connections, finally cleaned ground on starter, engine block, electrical bus and panel. Engine started without a hitch. Same fix for a tachometer issue.

Dagnabbit, dem old geezers sure knew stuff, didn't dey?


And some things never change.

[Yellowjacket]

Originally Posted by Stu Jackson

Dagnabbit, dem old geezers sure knew stuff, didn't dey?
And some things never change.

What's worse is that I'm approaching geezer status myself, and still have so much to learn. Still, always willing to share my ignorance.

[Gary Matthesen]

I put in 4 new golf cart batteries in my Catalina 36. Went to start, turned over weak and slow not fast enough to start. In my new to me boat there were two ground wires. Installing the batteries one got buried and never connected. I was ready to start replacing the starter, nothing but inadequate ground amperage capacity.

[Richard Kollmann]

Did you find the Yanmar fuse hidden in the ignition wire or do the lights only go off when you push the start button?

[Gripfast]

Had the same problem on my 3 gm 30 f. Put up with it for a few years and somewhere on this site i read that there quite a few conections in the wiring harness and at each one, the oem untinned wire corrodes at the connection. Dont know if that is true, but i ran a new #12 wire from button to starter selonoid and it fixed the problem.
Two years now, no troublem starting.