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Starter battery


Detling

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I had problems a few weeks ago starting the Isuzu 42 engine, if I jump leaded from the domestic started fine. Got to the marina went home got a new battery 950 CCA so far so good. I have fitted it and again it won't start the engine unaided I can jump lead domestics or the old battery and instant starting. The alarm goes as normal when the key is turned in all cases, there is a clicking and the engine tries to turn on one battery, on two batteries louder clicking and engine starts as it should. I have checked all joints, unbolted cleaned and rebolted,  and bypassed the isolator to eliminate that. The old battery was 7 years old and 1000 CCA. Someone has mentioned starter motor bushes, any other ideas. I understand 700 CCA is the recommended battery by Isuzu.  Volts drop to 11.6 at battery not sure about starter motor end, the clamp meter snows overload on the 300 amp range so something is making the engine hard to turn, and it is out of gear.

 

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>300 Amps on a cold diesel doesn't sound too excessive.

 

If it drops to 11.6 at the battery when pulling >300 amps then it would be interesting to see the terminal voltage at the starter when its cranking.

 

I know it was in a car but I had problems on my Cavalier when the earth strap (which was a braided flat copper wire) started to corrode and it simply swallowed everything up....

 

So have you checked the resistance between the engine casing and the starter battery negative...

Edited by StephenA
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26 minutes ago, Detling said:

the clamp meter snows overload on the 300 amp range so something is making the engine hard to turn

 

No not really. 300A is on the low side, I'd expect 400-ish.

 

The 'overload' means the meter is overloaded, not the starter.

 

 

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Yes the meter only goes up to 300 and shows OL so I know that it is above 300 amps but don't know if it is 400 or 600 for example. If there was an earth fault surely we wouldn't get the current flow we do, similarly if it were the solenoid or brushes why would doubling up the cranking amps with two batteries have the desired effect. It seems as though the engine is taking more power to turn it over, strangely  enough this did start after I got the most enormous teddy bear round the prop, it didn't stall the engine but made it cough and I stopped it, then it was hard to start, probably the last time it did so on one battery. But as said the engine is in neutral so I can't see any connection.

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Bypass and check out the starter motor direct from one good battery. Connect a good quality jump lead from starter  pos+battery post to the main large IN terminal on the starter solenoid, the one which should have a heavy red cable on it. With a thin wire connect one end also to that terminal and touch the other end of it to the small actuator terminal  alongside it on the solenoid at which point the starter should work and turn the engine over.  You can also connect the other black jump lead to the neg- post on the same battery with the other end clamped to the engine mass as close to the starter as possible.

   Be careful of touching the starter body or engine mass with the pos + jump lead.  Best to connect it to the starter solenoid terminal first before connecting the other end to the battery. 

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52 minutes ago, bizzard said:

Bypass and check out the starter motor direct from one good battery. Connect a good quality jump lead from starter  pos+battery post to the main large IN terminal on the starter solenoid, the one which should have a heavy red cable on it. With a thin wire connect one end also to that terminal and touch the other end of it to the small actuator terminal  alongside it on the solenoid at which point the starter should work and turn the engine over.  You can also connect the other black jump lead to the neg- post on the same battery with the other end clamped to the engine mass as close to the starter as possible.

   Be careful of touching the starter body or engine mass with the pos + jump lead.  Best to connect it to the starter solenoid terminal first before connecting the other end to the battery. 

Almost done that with jump from old battery to starter contact started fine that is when I decided to bypass the isolator as basically that was the only difference. My memory isn't that great these days so possibly still had new battery connected when I jumped to starter which would make more sense.  She who must, is now demanding  coffee and cake so I shall give in and sleep on it

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Prize goes to those who suggested earth / negative.  An example of why soldering on a crimp eye is not good.  My hull connection like many goes onto the engine bearers, unfortunately when climbing around in the engine bay they make good foot holds, result a lot of flexing of the cable. This had 75% broken inside the black sleeving, so it looked good, felt fine ,but wasn't up to the job of carrying the starter current.  Thanks for your help.

  • Greenie 1
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2 hours ago, Detling said:

Prize goes to those who suggested earth / negative.  An example of why soldering on a crimp eye is not good.  My hull connection like many goes onto the engine bearers, unfortunately when climbing around in the engine bay they make good foot holds, result a lot of flexing of the cable. This had 75% broken inside the black sleeving, so it looked good, felt fine ,but wasn't up to the job of carrying the starter current.  Thanks for your help.

 

Glad you've got it sorted - should make battery charging better too.

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