Dual Tank Switch Causing HP Fuel Pump to Shutoff?

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TruckCo

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Jay
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87
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C10
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350
For some reason I don't believe my switch is working. Yesterday when swapping over to the DS tank, my truck immediately died, no sputtering, no delay, it just instantly died. Cranked and cranked and nothing happened. When I switched to the PS with the key on, the fuel gauge pegged to 3 O'clock . When I pressed it again nothing happened and it just stayed the same. I noticed both my in tank pumps ran just fine, but my pump on the frame rail was not on. I took my battery ground off and the second I reconnected it, I heard the high pressure fuel pump kick on momentarily and the fuel gauge when to 3/4 (Where it should be). The truck then fired right up.

Is there any way this switch can fail and cause problems like this? Is this normal that the switch or something wired to it controls my high pressure fuel pump? I assume it was the switch and not the valve itself, I heard that in 87 they swapped the switch a little bit and its a special switch for the TBI years.

Also last question, when I swapped tanks before when it was working the fuel gauge "bounce" into the correct fuel level. I have seen videos online where when someone hits the switch the fuel level will slowly adjust to what the tank actually has in it. Thank you
 

Ricko1966

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I've been watching to see if anybody jumped in here. I don't know what you are working on I also don't know what fuel pump you are referring to. I could probably answer your question. If I had those answers.
 

Grit dog

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I’ve been waiting to see if anyone would ask why you have a 3rd fuel pump on it?
Just kidding. I just saw this.
Or are you running TBI in tank pumps feeding a booster pump for a port injected fuel system?
Doesn’t solve your problem but could be the problem.
 

Ricko1966

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I’ve been waiting to see if anyone would ask why you have a 3rd fuel pump on it?
Just kidding. I just saw this.
Or are you running TBI in tank pumps feeding a booster pump for a port injected fuel system?
Doesn’t solve your problem but could be the problem.
I wasn't kidding I've been watching,thinking ,tbi pumps as pushers to. ?????
 

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