YANST (Yet Another No Start Thread) - fuel pump circuit issues - Page 2 - Defender Source
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  #21  
Old August 2nd, 2009, 12:19 PM
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jim pendleton
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Use a headlight.

Check the connection at the starter.

Short to ground, loose connection or bad cable will damage the alternator.
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  #22  
Old August 2nd, 2009, 01:55 PM
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Charles Galpin
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I'll post all the numbers later when I'm home but I did a number of tests. I had a 0.9v drop from the battery to the starter on the negative side(0.4 of that at the battery connector) while cranking the starter. After replacing the ground cables it is now 0.25 iirc.

I didn't have any cables for the positive side but will replace them too - I have a 0.4 voltage drop from the battery to the starter while cranking as well as to the alternator iirc.

I got another alternator, hopefully the last for a while.
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  #23  
Old August 2nd, 2009, 06:28 PM
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jim pendleton
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I have seen the rectifier assemblies that go bad on the alternator for sale on ebay uk. Sounds like you are getting to the bottom of it.
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  #24  
Old August 2nd, 2009, 06:32 PM
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Charles Galpin
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Ok, here is what I found

Battery voltage: 12.87v idle, 11.73v while cranking the starter.
Voltage at starter: 12.75v idle, 10.3v while cranking

Voltage drop on positive side battery to starter while cranking 0.4 (I believe under 0.6 is ok)

Voltage drop on positive side battery to alternator while cranking 0.4

Voltage drop on negative side battery to starter housing while cranking 0.9. I replaced the ground cable from the battery to the frame to the transfer case and it's now 0.2.

I took a few other measurements, but those are the biggies.

Thanks for all the help. I'm hoping this resolves the issue but time will tell. If you think there is anything else I should do/check, please let me know.

charles
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  #25  
Old August 2nd, 2009, 06:33 PM
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jim pendleton
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.9 and .4 are quite a bit. Unfortuneatly if you are not loading current through the circuit it is hard to get an acurate voltage drop reading. For instance running the headlight off the suspect cables and then taking a voltage drop reading.

Google a product called Teslite. It should shoe accurate testing procudures for voltage drop test with a circuit loaded.

Quote:
Originally Posted by cgalpin
I'll post all the numbers later when I'm home but I did a number of tests. I had a 0.9v drop from the battery to the starter on the negative side(0.4 of that at the battery connector) while cranking the starter. After replacing the ground cables it is now 0.25 iirc.

I didn't have any cables for the positive side but will replace them too - I have a 0.4 voltage drop from the battery to the starter while cranking as well as to the alternator iirc.

I got another alternator, hopefully the last for a while.
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  #26  
Old August 2nd, 2009, 11:23 PM
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Charles Galpin
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Jim those numbers were taken under load - the ultimate load of the starter cranking (with the fuel pump relay removed).

Also that .9 is now .2 after replacing the ground cable.
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