Can't start engine

[Atlantic Salt]

I installed new marine batteries last year and the starting battery worked fine. Engine (yanmar GM30) started fit up each time. This year it won't start with just starting battery. I have to switch to house and starting batteries to start. Would a loose or poor ground on the starting battery do that. The starting battery reads about 12.6 volts. Any other suggestions?


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[the_alpine]

Your start batt is dead/low

[SteveInMD]

It could certainly be a bad connection. Don't over complicate the diagnosis. Just start at one point in the circuit (for example, the starting battery), use a meter and go step by step checking for secure, clean, tight connection and proper voltage at each connection point in the circuit.

[zeehag]

as 12.7 is full charge, perhaps you have other issues. do you have any sound at all when cranking ? if so, check connectors. first thing connectors. donot try for long .no more than 5 seconds.
i found that i need both house and starting batts to crank my diesel. most diesels need 1000 amp cranking... so might be just the cranking battery hasnt enough amps to start engine sola.

side note--i noticed when my charging system was touched by malevolent hands that i could no longer charge my cranker. i ultimately included it into my primary house bank.
next set of batteries i will return to use of deep cycle battery group 31 for cranker. seems to work better that way.

[leftbrainstuff]

Originally Posted by Atlantic Salt

I installed new marine batteries last year and the starting battery worked fine. Engine (yanmar GM30) started fit up each time. This year it won't start with just starting battery. I have to switch to house and starting batteries to start. Would a loose or poor ground on the starting battery do that. The starting battery reads about 12.6 volts. Any other suggestions?


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Standing voltage gives no indication of load voltage drop. If your start battery drops below 10V with the solenoid engaged you could have a useless battery or bad connections.

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[TeddyDiver]

Originally Posted by leftbrainstuff

Standing voltage gives no indication of load voltage drop. If your start battery drops below 10V with the solenoid engaged you could have a useless battery or bad connections.

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^ what he says Easier thou is to clean the connections..

[Jim Cate]

i found that i need both house and starting batts to crank my diesel. most diesels need 1000 amp cranking...

Zee, you might want to check that number. I believe that for most of our ~20-80 hp diesels the number is more like 200 max. I have a 250 amp fuse i n my starter circuit and it has never blown.

Jim

[skipmac]

Concur with Leftbrainstuff and Teddydiver. You can find full voltage with a weak or corroded connection until you apply a load when the bad connection will not pass current. Especially a problem with high current loads like a starter motor.

Look for loose or corroded connections between the battery and starter AND don't forget to check the ground side.

[bill good]

The Yanmar Plugs & sockets at the engine on this series gives a lot of trouble. Same advise as just given to "Lokas" today!! The house battery could be supplying some missing voltage to the starter circuits via other means than the standard wiring harness supplied. (assuming the starter battery has been fully charged & load tested)

You are lucky you have only one GM!! I've got 2!!

Regards

[macbeth]

Take out starter battery and go and get it load tested.
Is the house battery involved in starting ? Eg supplies power to solenoid or glow plugs ? If so, get it tested also.
Got to make sure batteries are good before messing about looking for failed connections.
I had a problem with corroded wires. They were only copper, not tinned. Found by using a current detector.
Have starter battery on shore power charger while starting. Undo starter connection and use a friends battery to jump. All the above will help isolate the problem. Could be starter itself, connections, anything. Start at batteries and work up to starter


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[smac999]

Originally Posted by SteveInMD

It could certainly be a bad connection. Don't over complicate the diagnosis. Just start at one point in the circuit (for example, the starting battery), use a meter and go step by step checking for secure, clean, tight connection and proper voltage at each connection point in the circuit.

unless the engine is cranking he will have the same voltage up the whole circuit. checking voltage with no load doesn't find a weak connection.

[Omatako]

Leave the batteries exactly as they are and bridge the solenoid excitation wire to the positive terminal on the starter - if the starter cranks it is likely to be the Yanmar plug on the engine harness. These plugs are so troublesome I have long since replaced mine with another design.

If the starter doesn't crank then you should start with the tracing of dodgy terminals/connections as recommended in other posts.

[Atlantic Salt]

What luck. I took the advice and started to check connections from the battery to engine. When I checked the main starter barely switch I found that it was not completely tight. Too tight to notice by hand but when I put a wrench on it I was able to get a full rotation. Tried the engine and it started right up.

Thanks for all the suggestions.
P

[skipmac]

Originally Posted by Atlantic Salt

What luck. I took the advice and started to check connections from the battery to engine. When I checked the main starter barely switch I found that it was not completely tight. Too tight to notice by hand but when I put a wrench on it I was able to get a full rotation. Tried the engine and it started right up.

Thanks for all the suggestions.
P

Congratulations and thanks for reporting the outcome. Always educational for all of is to find out what solved the problem.

My philosophy, always try the easy and obvious first. 9 times out of 10 it solves the problem and saves you a huge amount of work.

Well maybe not 9 times out of 10 but a lot of times anyway.

[RaymondR]

I had a problem with cranking batteries a while back even though they were fairly new batteries. Turned out that the washers supplied for the studded connections were SS and since there were 4 included with each battery I put one either side of the wire terminal. The resistance through the SS washers was sufficient to cause a large voltage drop under the high cranking current. Removed the SS washers and all was OK.


Strange but true.