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Onan Generators

Onan 4b


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  #1  
Old 04-10-2017, 11:32:24 PM
jakemiller09 jakemiller09 is offline
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Default Onan 4b

Hello everyone, I have an onan generator in my motor home and I'm having issues with the fuel pump voltage. When cranking wire R7-2 is only getting 8.9v I can make the pump turn on with an alternative 12v source. What could be causing this issue?
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  #2  
Old 04-10-2017, 11:38:58 PM
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BigBlockChev BigBlockChev is offline
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Default Re: Onan 4b

Please post the full model and serial# for your generator so we know what you have and can provide appropriate advice. Someone will be along shortly to help. Cheers Dan
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Old 04-11-2017, 12:04:34 AM
jakemiller09 jakemiller09 is offline
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Default Re: Onan 4b

Serial # f880131937
Model # 4bgefa26100f
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Old 04-11-2017, 11:07:32 AM
len k len k is offline
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Default Re: Onan 4b

I assume R7-2 is the wire on pump side of the resistor. Bad wire connection maybe??

Check if voltage rises to 12V during cranking, if not maybe diode cr9 is blown. Better yet see if both sides of cr9 are connected to anything, maybe wire got pulled off.
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Old 04-11-2017, 11:46:09 AM
jakemiller09 jakemiller09 is offline
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Default Re: Onan 4b

I checked voltage going into that ceramic resistor deal and it's 8.9v followed the wire back and it goes to the main switch board
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Old 04-11-2017, 11:52:50 AM
len k len k is offline
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Default Re: Onan 4b

Cranking engine draws lot of amps from bat, if bat is weak it's voltage might be dropping to ~9V.

While cranking, Check voltage across bat and also across input to control board.

If that's good check voltage across spark coil while cranking
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