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I have now concluded that it must be aerated in the pump, but how? and where does the air come from?
Diesel fuel that appears "clear" and "solid" will actually have about 10% air dissolved in it. When you put it through the violence and pressure changes of the pump and injectors (because some of that return fuel is bleed from the injectors), then the dissolved air basically gets "jarred" into forming bubbles in the fuel.
 

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Does anyone use a screen or some type of filter in the tank? Is it necessary?
My '79 had a screen in tank, but over the years enough crud entered the tank to obstruct flow. I removed the screen and added a disposable 3/8" inline filter in the line from tank to pump to catch the chunks. I am soon upgrading to a LARGE Fleetguard filter, in line between tank and pump.
 

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Diesel fuel that appears "clear" and "solid" will actually have about 10% air dissolved in it. When you put it through the violence and pressure changes of the pump and injectors (because some of that return fuel is bleed from the injectors), then the dissolved air basically gets "jarred" into forming bubbles in the fuel.
Thanks, I hope the diesel I buy at the pump isn't 10% air.
This then must mean that the diesel being injected must be 10% air aswell.

Gaza
 

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Thanks, I hope the diesel I buy at the pump isn't 10% air.
This then must mean that the diesel being injected must be 10% air aswell.

Gaza
From Caterpillar Special Instruction 651-1250:

"Normally No. 2 Diesel Fuel contains about 10% air in solution, although the air is not visible."

That's about the size of it...

It does vary with temperature, ambient pressure, etc, but that's the number I keep seeing as a "baseline average".
 
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