Gear Pump Testing

[Rawze]

Simply replacing a worn gear pump and electric lift pump on a CM870 or CM871 is not going to make a 1 mpg difference unless one of them was sucking some air... or you were getting low pressure fuel problems that were noticeable, causing CEL lights to come on. Something does not add up properly in your statements there.

I have more than 1.4 million original miles on my gear pump and electric lift pump, and I still get 9+ mpg with the truck while loaded heavy, everywhere it goes.

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Also if you suspect a burnt/leaky valve causing compression loss, then you need to remove all the rocker arms and pressurize the intake manifold up at 30 psi and listen/check for leakage while all the valves are shut... and then do the test at the exhaust manifold.

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You also need to do an overhead adjustment on it and do a proper injector leak test on it...
http://rawze.com/forums/showthread.php?t...8#pid67948