engine start problem, battery or not?

[Mandarin331]

Although the engine usually starts fine on the engine battery there have now been two occasions this year when it's failed.

What happens is that the glow plug light comes on on the first turn of then key, but on the next 1/4 turn (to turn the starter) the power disappears and there's not even a click from the solenoid. We then switched to the domestic battery and the engine starts immediately.

Next time it will work fine on the engine battery.

The engine battery is showing between 12.5 and 13 volts, and holds this charge when left for 2-3 weeks between uses. It's a 3 year old Ford transit battery and the engine is a 20 hp vetus m3.

Could this be a battery fault, a 1,2 both switch fault or ???

 

[vyv_cox]

It sounds like high resistance in the line between the switch and the solenoid connection on the starter motor. Next time it happens try connecting a short jumper lead from the battery supply to the starter motor, 8 or 10 mm terminal, directly to the solenoid connection on the starter motor. This will bypass all the wiring, relays, switch, etc. If the motor then starts you need to check everything in the wiring and possibly replace the switch.

 

[savageseadog]

If you have a meter make a measurement directly across the battery terminals as you try to start it. It will read 12-13V before and around 10V as you try to start. Any less it's the battery that's had it. If it hardly drops, say, 0.5V or less then it's the wiring, contacts, battery switch, aolenoid or starter as vyv_cox says.

 

[jwilson]

Although the engine usually starts fine on the engine battery there have now been two occasions this year when it's failed.

What happens is that the glow plug light comes on on the first turn of then key, but on the next 1/4 turn (to turn the starter) the power disappears and there's not even a click from the solenoid. We then switched to the domestic battery and the engine starts immediately.

Next time it will work fine on the engine battery.

The engine battery is showing between 12.5 and 13 volts, and holds this charge when left for 2-3 weeks between uses. It's a 3 year old Ford transit battery and the engine is a 20 hp vetus m3.

Could this be a battery fault, a 1,2 both switch fault or ???

Sounds like 99% likely to be a battery cable bad connection somewhere ....

 

[Mandarin331]

Thanks for all the quick input. Doing more checks we've now found that whilst switching the batteries through 'both' causes the CD player to restart, so clearly a temporary gap in power where there shouldn't be, so the battery switch is suspect anyway.

With regards to the voltage drop I would try that, however the problem is that 9 time out of 10 it works fine (but I'm not happy with an engine that won't start 10/10).

Have left the boat now, but next time I'll test the resistance etc and see if the battery switch can be opened up, its a Hella Marine one.

 

[VicS]

Could this be a battery fault, a 1,2 both switch fault or ???

If this truly only occurs when using the starter battery and never when using the domestic battery the places to look are the connections to the starter battery and also the 1,2,b switch

 

[pmagowan]

I would want to find out pretty urgently. Prior to me rewiring I once had a pernickety problem like this and it turned out that the main lead from the start battery was completely broken from vibration and corrosion. It was just sitting there and the current seemed to pass it ok sometimes as the two ends were touching but it could easily have dropped off and shorted out causing a fire. When I went to examine the connections it came away in my hand. My new connections have been made up with glued heatshrink so that the terminal is strongly connected to the wire which avoids corrosion and strengthens the joint.

 

[Mandarin331]

I would want to find out pretty urgently. Prior to me rewiring I once had a pernickety problem like this and it turned out that the main lead from the start battery was completely broken from vibration and corrosion. It was just sitting there and the current seemed to pass it ok sometimes as the two ends were touching but it could easily have dropped off and shorted out causing a fire. When I went to examine the connections it came away in my hand. My new connections have been made up with glued heatshrink so that the terminal is strongly connected to the wire which avoids corrosion and strengthens the joint.

Interesting, when I was first looking at this I found the positive terminal clamp had cracked and was therefore loose on the battery post. I hoped that was it but after replacing it the problem reocurred yesterday. So next step will be the switch.