Truck stalls when I select left tank

[JohnKimble]

Last week I replaced the three (3) short rubber fuel lines that go between the sending unit and the hard lines for the left tank of my truck.

Now once my truck is running, if I select the left tank, after about ~1 minute at idle, the truck dies. With the right tank, no issues at all.

I'm thinking I must have done something when replacing the lines from the sending unit to the hard lines. From what I remember, I reconnected them in the same order from the sending unit to the hard lines. The sending unit line near the front of the truck went to the first hard line near the front of the truck. Middle to middle, and rear on sending unit to rear hard line. I'm thinking maybe that wasn't the correct order?

Any suggestions?

[JohnKimble]

Also, the left tank has some pressure to it when I remove the gas cap after I try to run the truck (until it dies). I tried running it with the gas cap off, it still dies after about 1-2 minutes after switching from the right tank at idle. The gas gauge also displays the correct level for both tanks.

[05duramaxhd]

Had the same issue ended up putting new hard line under the cab and it fixed it

[gmachinz]

The sending units go bad over time-the screen literally deteriorates and it lets crap get into the crossover line. I priced a set of lines from Inline Tube because I didn't want to mess with any old fuel lines. $232 total for pump supply/return to selector valve and the crossover lines with all the correct frame clamps. My lines had crud and rust inside of them.

[JohnKimble]

I can see a sending unit going bad, but I feel it's a coincidence it went bad the day after I dropped my tank. I'm starting to think I possibly clamped the rubber hoses too tight???

[Robert1970C20rstbukt]

I had the same problem on my '84 dually recently, but with both tanks. I ended up pulling the sending units and cleaning them. They really weren't too rusty and both were showing correct readings on the gauge, but the pickup screens deteriorated and pieces of them clogged the lines up. Once I got everything loose I blew all the lines out with air, haven't had a problem since. The steel lines were surprisingly clean as well. I bought new pickup screens to put on the sending units as well, the part number is 5651711.

[hatzie]

Assuming this is a 1981-1986 CK or 1987-1991 RV pickup truck...
The 3/8" ports are supply and the 5/16" ports are returns.
The engine side of the valve only has one of each. To and from the engine.
The tank side of the valve has a pair for each side. To and from a tank. The motorized valve shuttle only opens one set of these.

[Corts60]

When the switching valve fails, it defaults to the passenger tank. Perhaps the valve died.

[JohnKimble]

Originally Posted by Corts60

When the switching valve fails, it defaults to the passenger tank. Perhaps the valve died.

Well I can still select the left tank and I hear the buzzing of the valve like normal?

[hatzie]

Originally Posted by Corts60

When the switching valve fails, it defaults to the passenger tank. Perhaps the valve died.

Not always.

You are correct for 1980 and prior GM pickups with solenoid tank valves.

1981 and later motorized tank valves retain the last selected position. If they fail in that position that's where they stay.

[JohnKimble]

Originally Posted by hatzie

Not always.

You are correct for 1980 and prior GM pickups with solenoid tank valves.

1981 and later motorized tank valves retain the last selected position. If they fail in that position that's where they stay.

Thanks again Hatzie. I'm guessing a fuel line got disconnected or maybe connected too tight. Possibly the sending unit. I'll have to pull it again and see

Hatzie you're my square body guardian angel mechanic. I owe you a lot of beer.

[hatzie]

You can't tighten hose clamps enough to collapse the steel sender nipples or the steel fuel lines.
I'd disconnect the supply line crossover tube from the valve and the tank and blow shop air through it from the valve end.
Check that you didn't kink a hose when you put the tank in place. I usually try to put a loop in each of the three hoses rather than straight onto the lines.
For the SAE J30R9 "rubber" tank lines I'm a big fan of the constant tension band clamps for ease of installation on small lines and in tight places. No worries about not getting them tight enough or too tight either.

[JohnKimble]

I'm in the middle of working on this. I dropped the tank, short rubber lines looked okay. I removed them and noticed they each had a crease, so I'm thinking I must have kinked them when i reinstalled the tank. I ran a hose from the supply line to a 5 gallon tank to see if it's pulling fuel, and it is. Reinstalled the 3 lines with the tank semi-dropped and it's running with no issues. I'm thinking I must have kinked the lines during the reinstall. I'm an idiot.

[JohnKimble]

Reinstalled with shorter lines, all is well. Thanks for everyone's input!