Starter Battery wiring

[dmksails]

I'm having trouble where the starter battery is not providing enough power to turn the engine over (Yanmar 3GM30f with an 800 CCA Grp 24 battery). With the selector switch on the Starter battery it will make one or maybe 2 slow grinds, then nothing.

If I place the battery switch to the house bank or to the both setting, then the engine starts fine after one or 2 fast grinds.

So, somewhere in the starter circuit I'm loosing amps. I've had the battery tested and they say it's fine, but it wasn't a load test. I've check out the cabling. I've 2/0 cable that goes from the battery + to the battery switch, then from the switch to the starter. The ground goes from the starter battery (-) term to a bus bar. Another cable goes from the bar to the engine.

Should I have the starter battery (-) term go straight to the engine, then another 2/0 cable from the engine to the bus bar? I'm not sure why that would matter, but I've tried everything else. And yes, I've cleaned and tighten all power and ground terminals.

[Uncle Bob]

Originally Posted by dmksails

I'm having trouble where the starter battery is not providing enough power to turn the engine over (Yanmar 3GM30f with an 800 CCA Grp 24 battery). With the selector switch on the Starter battery it will make one or maybe 2 slow grinds, then nothing.

If I place the battery switch to the house bank or to the both setting, then the engine starts fine after one or 2 fast grinds.

So, somewhere in the starter circuit I'm loosing amps. I've had the battery tested and they say it's fine, but it wasn't a load test. I've check out the cabling. I've 2/0 cable that goes from the battery + to the battery switch, then from the switch to the starter. The ground goes from the starter battery (-) term to a bus bar. Another cable goes from the bar to the engine.

Should I have the starter battery (-) term go straight to the engine, then another 2/0 cable from the engine to the bus bar? I'm not sure why that would matter, but I've tried everything else. And yes, I've cleaned and tighten all power and ground terminals.

My question would be if they didn't do a load test how can they say it is fine? Sounds to me like a nearly dead battery.

[wsmurdoch]

With a friend and a voltmeter check the voltage as you start the engine at the battery lead terminals (- to +) then move around the circuit moving the + lead from the battery, through the whole circuit, finally coming back to the - lead post on the battery. Somewhere you will find where the problem is. It may be the battery itself, maybe the terminals on the battery, maybe the wiring, maybe....

Bill

[roverhi]

Starter problems are often the ground. Run that 2/0 ground cable direct to the battery or engine block leaving out the bus bar. If that doesn't solve the problem, it's probably the battery. A group 24 is more than sufficient to start a 3GM30.

A load test is the only to see if there is an internal problem in the battery. Just checking voltage or a hydrometer won't tell you all there is to know about the battery condition.

[Davo1404]

I had the same problem with my 2gm20f for years. If the start battery was slightly down in voltage wouldn't start or just click. Replaced battery, starter button & checked all the wiring, especially connectors. Then read that The starting circuit wiring is under size & prone to voltage drop. Got a marine electrician who confirmed that there was only 11.8 volts at the starter motor when pressing the starter button. He said easily fixed & fitted a relay right beside the starter motor. No problems since.

[smac999]

if the pos cable goes to the same switch as the house battery. and the ground goes to the same bus as the house battery. and the house battery starts it.

it's either a bad battery, bad switch. or bad cable from battery to switch or battery to bus. everything else past that point would be fine if the house can do it. otherwise the house would not start it either.

you need to measure the battery voltage while trying to crank it. at the battery.

[smac999]

Originally Posted by Davo1404

I had the same problem with my 2gm20f for years. If the start battery was slightly down in voltage wouldn't start or just click. Replaced battery, starter button & checked all the wiring, especially connectors. Then read that The starting circuit wiring is under size & prone to voltage drop. Got a marine electrician who confirmed that there was only 11.8 volts at the starter motor when pressing the starter button. He said easily fixed & fitted a relay right beside the starter motor. No problems since.

11.8 at starter is pretty high and good.

[Wotname]

Originally Posted by smac999

if the pos cable goes to the same switch as the house battery. and the ground goes to the same bus as the house battery. and the house battery starts it.

it's either a bad battery, bad switch. or bad cable from battery to switch or battery to bus. everything else past that point would be fine if the house can do it. otherwise the house would not start it either.

you need to measure the battery voltage while trying to crank it. at the battery.

This is the key!

To repeat, if the house battery starts it OK, the most of the starting circuit is OK.
As smac999 suggests, you have a bad start battery (most likely) or bad wiring from the start battery to the main switch (less likely) or a failed main switch (least likely).

And to repeat smac999's advice - use your meter while cranking the engine, this will confirm the faulty item.

[GordMay]

Originally Posted by Wotname

This is the key!
To repeat, if the house battery starts it OK, the most of the starting circuit is OK.
As smac999 suggests, you have a bad start battery (most likely) or bad wiring from the start battery to the main switch (less likely) or a failed main switch (least likely).
And to repeat smac999's advice - use your meter while cranking the engine, this will confirm the faulty item.

Indeed.

Originally Posted by wsmurdoch

With a friend and a voltmeter...Bill

One of the more useful tools, for electrical troubleshooting (especially start systems), is a “remote starter switch”. It might enable you to eliminate the “have a friend ...” from many procedures.
➥ https://www.autozone.com/test-scan-a...starter-switch