Fully charged battery won't turn engine

NickNap

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Fully charged battery won\'t turn engine

Used a replacement battery for first time this morning and despite being fully charged (bought it new and charged last week) it turned the engine over slowly a couple of times and soon became too slow to start up. It now measures 13.08 accross terminals so seems charged.
It's a lead acid leisure battery which was a straight replacement. I'm wondering if I have a connection or switch problem as I can't think off another reason why a new battery showing that voltage wouldn't turn the engine over (the terminals, etc look clean) - anyone have any ideas?

Thanks
Nick
 

ccscott49

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Re: Fully charged battery won\'t turn engine

It's more than likely a loose or corroded connection, in your main cables to the solenoid and starter motor. Or the earth from your engine to the battery, same thing really, check all the connections, I bet you'll find it.
 

andy01842

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Re: Fully charged battery won\'t turn engine

quick way to find it, the bad connection will be hot arfter turning the engine over! check the voltage accros the battery when the engine is being turned. if the voltage is high, i,e 12v plus it a bad connection. if the voltage is low i.e. lower than 9v it the battery.
 

vyv_cox

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Re: Fully charged battery won\'t turn engine

Did it turn over previously, with another battery? If it did then there is a problem with connections, either of the battery leads or the starter motor connections. If it didn't, first thing to do is turn the engine over with a handle, if fitted, or with a spanner on the nut at the end of the crankshaft. If it is extremely stiff, not including any compression pressure, you need to investigate further.
 
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Anonymous

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Re: Fully charged battery won\'t turn engine

13V across the terminals is not conclusive. Are you really sure that it is/was fully charged? Assuming that it is not an open battery or, if it is, that it is not convenient to check the SG of the acid, then you need to check charge yourself. Can you put it on charge, yourself, and watch the terminal volts go to a high level (14.2 or higher depending on the type of battery)? Only when the battery has been at that voltage for a half an hour or so AND drawing minimal current at the same time (<2A) can you be sure that you have a fully charged battery.

It is worth checking all the terminals very carefully, but before pulling things to pieces do check that your battery is fully charged.
 

Como

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Re: Fully charged battery won\'t turn engine

What is the voltage across the battery terminals while cranking the engine? If it falls below about 9 volts then the battery itself could be faulty despite being new. If the voltage stays high then the problem is with the wiring, connectors or switch.
 

rich

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Re: Fully charged battery won\'t turn engine

What happend to the old battery Did it start the engine,

When was the engine last run?
 

whipper_snapper

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Re: Fully charged battery won\'t turn engine

Put a voltmeter across the starter motor, what is the voltage ?
Crank the engine, what is the voltage ?

Then

Put the voltmeter across the battery terminal - the lead posts themselves - crank the engine. What happens ?

That will tell you what is happening.

If V at starter motor is same as battery, but falls very low (<10) when its working BUT the voltage at the battery stays high when cranking, then you have a bad connection.


If the V at the starter motor AND the battery fall very low when cranking, you have a duff battery.

If the V at the starter motor and battery stay high, you have a duff starter motor (or engine!).
 

oldharry

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Re: Fully charged battery won\'t turn engine

I recently had to deal with a starting problem like this: The battery was fine, the terminals were clean, correct voltages measured at various key points, but cranking was excruciatingly slow. It turned out a leaking coolant pipe had dripped seawater into the starter, and rusted the bearing at the bendix end. The starter armature could not be turned by hand at all.
 

Gargleblaster

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Re: Fully charged battery won\'t turn engine

[ QUOTE ]
If the V at the starter motor and battery stay high, you have a duff starter motor

[/ QUOTE ]

I went down for a sail for the weekend on Saturday. Only to find that my engine wouldn't start. Just got that annoying clicking noise. Checked both batteries both showing about 12.7 volts. tightened up battery terminals - no result. Cleaned every terminal I could find. Dismantled my alternator and water pump so I could take the terminals off the solenoid to clean them. Put water pump and alternator back - no result. Then went through the engine control panel and cleaned every terminal - even took the ignition switch apart, losing a spring in the process.
Finally a midday Sunday having had to clean out and then half dismantle my rear locker I emerge with a starter motor which I took home for my son-in-law to test. Yes it has a short. So instead of having a nice sail I spent the week up to my ears in grease and bilge water. Next weekend I have the joy of replacing my starter motor.
 
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Anonymous

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Re: Fully charged battery won\'t turn engine

[ QUOTE ]
I emerge with a starter motor which I took home for my son-in-law to test. Yes it has a short.

[/ QUOTE ]The resistance of the windings of a starter motor are VERY low and you would need to be a bit clued-up and be able to use a good digital voltmeter accurately, to diagnose a short. Do check that you actually have a duff starter before changing it.

If you are going to test it, you must not, under any circumstances, let it run under no load as this type of motor has no limit to how fast it can spin (it could break apart). To test it at home, if you have some jump leads, attach the black lead to your car neg and the starter chassis, connect the red lead to your batt pos and connect it to the starter via a a couple of inches of around 10A wire to act as a resistance and fuse. Don't physically attach it, just dab it on and be prepared to pull it away quickly, breaking the connection, if it turns out to be a short, or the motor spins. Don't touch the short 10A cable as it might get very hot - hold the jump leads croc clip. I hope that makes sense.

Don't let the motor spin up. If it starts to spin then there is no short and you probably need to look elsewhere for the problem.
 

whipper_snapper

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Re: Fully charged battery won\'t turn engine

[ QUOTE ]
Cleaned every terminal I could find. Dismantled my alternator and water pump so I could take the terminals off the solenoid to clean them. Put water pump and alternator back - no result. Then went through the engine control panel and cleaned every terminal - even took the ignition switch apart, losing a spring in the process.

[/ QUOTE ]

Simply wielding a multimeter to measure the voltage at various points while cranking/trying to crank can be very informative, and may have saved a lot of time and effort. Still, it’s all character-building stuff!
 
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