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I have a 1988 Chevrolet 3500 with a 454 and when you switch from left tank to right tank truck engine leans out...i have personally changed both pumps ( 1 in each tank) i have changed the switch valve and the switch in the cab, new lines from tanks to switch valve and for the heck of it i just changed the right tank pump again. The reason i know it leaning out cause you can hear the difference in the motor when switching and while watching my scanner i can see block learn(145) going up and the integrator staying low(128) on the right tank and the block learn and integrator matching on the left tank.....any ideas?

Thanks ...Bruce
 

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Not sure if this would have 2 different fuel filters, (one for each tank) but are all the equipted fuel filters new and clean? I belive that between then fuel pump and the sending units on those there is a rubber hose conecting the pump to the SU. Make sure that its not leaking or that it has a hole in it. Or that any possable rubber hoses in the system arn't kinked a little. Do both pumps also have new fuel strainers on them as well?


Hope this helps a little good luck!
 

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Fuel strainers in both tanks are new..fuel line from tanks to fuel switch valve new, there is 1 filter and its a common filter that is after the fuel switching valve.

Not sure if computer tied in to fuel tank switch or not...these computers back then where so primitive.
 

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I'd take a look at the grounds for the pumps. If one of them is a little loose or dirty, it will affect the pump's ability to work correctly.
Good Luck and God Bless
 
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