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73-87 Chevy _ GMC Trucks => Fuel Systems and Drivability => Topic started by: shinkle on April 10, 2021, 11:24:14 AM

Title: Dual tank switch kills the engine
Post by: shinkle on April 10, 2021, 11:24:14 AM

I have an 87 R10 dual tank.  The driver side tank and gauge works great.  When I flip the tank switch to the passenger side the engine instantly dies.  I replaced the switch and put gas in the passenger tank.

Any suggestions?

Title: Re: Dual tank switch kills the engine
Post by: MIKE S on April 10, 2021, 01:21:16 PM

More than likely the in tank fuel pump in the passenger tank is bad.

Title: Re: Dual tank switch kills the engine
Post by: bd on April 10, 2021, 01:26:23 PM

Do you hear the tank selector valve located below the cab ratchet when you switch tanks?  Does the fuel gauge switch tanks?  The motorized valve may not be moving full rack to select the opposite tank.  Alternatives could be a faulty in-tank fuel pump, poor continuity somewhere between the dash switch and the fuel pump, or a faulty fuel pump ground.

Fuel System Schematics (and fuel gauge troubleshooting) (http://forum.73-87chevytrucks.com/smforum/index.php?topic=9072.msg301331#msg301331)

Title: Re: Dual tank switch kills the engine
Post by: shinkle on April 11, 2021, 02:49:13 PM

If I flip the switch to the passenger side and turn the ignition key, I don't hear a click and whrrr sound.  If I try it on the good driver side I definetly hear the click and whrrrrr.  The gauge does not work on the bad passenger side.

Title: Re: Dual tank switch kills the engine
Post by: bd on April 11, 2021, 03:59:09 PM

There is a 3" long red pigtail terminated by a black insulator hanging freely from the fuel pump relay located at the top of the engine compartment firewall on the passenger side of center.  Connect a 20-amp fuse-protected jumper between the free end of the pigtail and the firewall junction block stud (B+) located nearby on the firewall above the driver-side valve cover.  With the ignition switched OFF and the passenger fuel tank selected, do you hear the fuel pump running in the passenger side tank?

Title: Re: Dual tank switch kills the engine
Post by: All_American_C10s on April 14, 2021, 05:25:30 PM

Quote from: MIKE S on April 10, 2021, 01:21:16 PM

More than likely the in tank fuel pump in the passenger tank is bad.

I bet you're right.  I had the exact same issue.  Ended up replacing the in-tank fuel pump on the bad side.

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