New to me 79 K10 left me stranded today.

[Greasey Harley]

I ended up with a '79 K10 long bed, 350/4-Speed/205
I rebuilt the engine, fuel system, brakes, clutch, axles, drive-lines, some new tires.
Went through the wiring, new hoses, belts, radiator, etc.etc.etc, got it up and running about a week ago.

Today, I left the gas station after filling the drivers side tank (which it was running off of), drove about 2 miles and it quit. Just shut off and would not start.
A quick inspection showed the accelerator pump wasn't functioning. Out of gas ????? WTH?

Apparently, the fuel diverter defaults to the right tank if it fails?? So, even though the switch was on left tank, and the gauge was reading the left tank it was pulling out of the right tank.

I hooked a little boat gas tank to the fuel pump, strapped it down to the passenger fender well and drove it home. Pretty frustrating to go through all that work and get stranded after the truck has only been together for a week.

These are simple machines and it took a half hour to patch it together enough to limp it home, and about 15 minutes on the internet to figure out why it broke down. I ain't mad, just didn't see that coming. Oh well, I'll have it up and running this weekend. Can't do that with modern trucks

I do love an old Square-Body 4x4
-Russ

[cadillac_al]

I have never had dual tanks so never experienced those gremlins. At least you knew what you were doing and got it home pretty quick.

[Palf70Step]

I will have to remember that if I ever get one with dual tanks. Glad yuou figured it out quickly.

[Dead Parrot]

If the valve is one of the earlier solenoid valves, they do have a default no power position. The later motor driven ones are supposed to stay in the last place selected until switched to the other side.

IIRC - earlier trucks had the passenger side as primary. I think later models switched primary to the driver's side.

Don't overlook the possibility that a mouse chewed on the wires and/or hoses. I had one bag both suction hoses in the same week. Rather irritating to have fuel starvation at the motor with 40 gallons of gas on board.

[jocko]

That’s correct, passenger side tank is primary, so it makes sense that that is the failsafe default. There are some great threads on here about the different tank switches that GM had over the years, very good reads. Glad you got it sorted out greasy and thanks for posting. While I did realize the passenger tank was the primary - was not aware it could failsafe to it regardless of switch position. Very helpful info.

Makes me wonder if a combo of the factory electrical selector switch and a mech switch might be a good thing. In other words, routing the output of the elec switch thru a mechanical 67-72 type valve, and then having the non-pri tank tapped additionally and fed to the other mech valve selector inlet. That way, if this happened, one could at least get the sec tank fuel via mech means if required.

[hatzie]

The 73-80 Solenoid valves have a default rest position. You can re-plumb it to the driver side by changing the hoses around if that's what floats your boat. You'll have to change the outside wires on the three terminal side of the switch as well to re-purpose the RH tank to the AUX position.

If your Solenoid Valve has failed and it has six hose positions, very likely on a 1979, I would highly recommend updating to the 1981 and later system... Nobody is making the older solenoid style six hose valve.

The motorized 81-91 valves don't change position til you ask em to and Pollack is still making them.

Here's the Tech writeup on the NL2 dual tank systems... http://67-72chevytrucks.com/vboard/s...d.php?t=754061