Starter motors, excitation.

[Barking Mat]

Evening.

I'm having an issue with starter motors, and it's doing my head in.

So, marine diesels, standard 4 cylinder 4 stroke blah, blah, blah.

Kubota 1.5 litre, Marinised by Nanni.

My issue:

Intermittently, they don't start, they click.

I've 12.7 volts in the starter battery, but only 10.5 arriving on the excitation terminal.

So I changed the key starter system, same symptoms.

So having changed the starter motor, the ignition swith, I can only conclude it's a loom problem.

Sod digging through the loom, I wire a push start button between the +ve starter motor feed and the excitation.

I give myself 3m 2x1.5 flex cable, same problem. Clicks, but doesn't engage the starter.

Going quietly mad, I cut through the cable at 1.5 m at it starts. (Wire cutters).

Help me please folks.

Never had so much problems with a starter motor, on one boat.

 

[tom2207]

check the earths ,,, it needs both sides of a cct to work, throw a lead from the engine / starter earth point to the battery and check voltage again ,,,

 

[Barking Mat]

Just to be clear, if you take a nice thick cable and jump +ve feed to excitation it will always start.

New starter motor, second in 4 months.

 

[Barking Mat]

check the earths ,,, it needs both sides of a cct to work

Just to be clear, if you take a nice thick cable and jump +ve feed to excitation it will always start.

New starter motor, second in 4 months.

 

[123hotchef]

nd check the ground wires and connections and chassis to battery ect

 

[Barking Mat]

check the earths ,,, it needs both sides of a cct to work

Sorry, I was slow in adding that.

 

[123hotchef]

Just to be clear, if you take a nice thick cable and jump +ve feed to excitation it will always start.

New starter motor, second in 4 months.

is there any relay in the equation?

 

[Barking Mat]

Seems to be an issue of resistance in the excitation circuit ??

is there any relay in the equation?

No.

But, I'm thinking this could be a solution.

This is a long standing unresolved company issue incidentally.

 

[tom2207]

Just to be clear, if you take a nice thick cable and jump +ve feed to excitation it will always start.

New starter motor, second in 4 months.

then the cable is the issue ,, if you put a cable straight to the motor and it run , but wont run with the cable thats there ,,, its the cable ,, i take it its running its own starter solenoid , nothing remote or fancy

 

[123hotchef]

Seems to be an issue of resistance in the excitation circuit ??

No.

But, I'm thinking this could be a solution.

This is a long standing unresolved company issue incidentally.

corrode wire in a connector somewhere maybe.
Go with the push switch and new wire idea!

 

[Barking Mat]

then the cable is the issue ,, if you put a cable straight to the motor and it run , but wont run with the cable thats there ,,, its the cable ,, i take it its running its own starter solenoid , nothing remote or fancy

Yes, but...

I thought I'd demonstrated a loom failure.

But with 3m of 2x1.5 cable it wouldn't start.

But with 1.5m of same cable it did.

I've not run an ampimetric clamp over it to see what ampage the excitation of a starter motor pulls, but I can only imagine that's the issue ???

Will investigate the integrity of the earth clamps on the engine, not to be ruled out, but strikes me as unlikely, but who knows ?

corrode wire in a connector somewhere maybe.
Go with the push switch and new wire idea!

Tried with new wires, length seems to dictate ???

 

[8ob]

Kubota starters are a ballache, they suffer with contactor pitting , they click in but make no contact.

 

[tom2207]

Im half way through doing a boat rewire at the moment , pre tinned 50mmsq multistrand marine cable is your friend , and no crimp only terminals , solder everything no matter what .

got a split charger / smart charger from a decent supplier and the 16sq cables for the unit to remote sensor were all crimped and heat shrunk ,,, long story short , half of them were grap and wouldnt have lasted a week at sea ,,, all soldered now and will do the next thirty years ,, my last boat was nearly 100 years old and was still on the original wiring , it was done properly with no expense spared the first time. ,,, do it right once , its hard to bump start a boat.

and you dont get oars with a fifty footer ,,,, just a 14ft boat hook .

 

[dan.taylor.1]

I'd be checking the wires, ounds like either a high resistance issue or a dodgy earth, not just the main chassis to engine earth's, but any on the circuit, like if your starter relay earth is pants it'll cause issues etc.

 

[Barking Mat]

Kubota starters are a ballache, they suffer with contactor pitting , they click in but make no contact.

I'm used to doing what your doing in that photo.

Know it well.

But this starter motor was new two weeks ago.

 

[tom2207]

Will investigate the integrity of the earth clamps on the engine, not to be ruled out, but strikes me as unlikely, but who knows ?
The earth is every bit as important as the positives ,,, it has to be a full circuit , meter the volts and look for a voltage drop , or drop the battery out of the cct and look for increased resistance ,,,[ or swing on the switch and see what smokes ] its a fair indicator too.

 

[scottmk1]

It’s another possibility that the cable has rubbed through the insulation somewhere and you have a partial earth fault, causing the voltage drop, hence not enough oomph at the starter motor

 

[Barking Mat]

On the loom, I've 12.7 on the main feed, but the excitation has 10.5, so I'm losing 2.2 volts, so I blame the ignition barrel, I changed it, same.

So I think it's the loom.

I bypass the loom.

Stick my cable inbetween the +ve feed and the excitation and a long cable nay, short cable yay.

 

[tom2207]

a small bit of wire and go from the main pos feed on the starter to starter relay and the thing should work grand ,, or jam a screwdriver across if its handy , if that starts it , its the loom so just run a couple of fresh wires in .

 

[Barking Mat]

a small bit of wire and go from the main pos feed on the starter to starter relay and the thing should work grand ,, or jam a screwdriver across if its handy , if that starts it , its the loom so just run a couple of fresh wires in .

That's what my issue is.

Big fat wire starts it.

3 m 2x1.5 doesnt.

1.5 m 2x1.5 does.