85 Silverado - Fuel Tank Selector Valve install - no fuel

[SilveradoDude]

I just installed a new Fuel Tank Selector Valve (AC Delco). The truck started right up after install but after the fuel in the line and carb were used up....no more fuel. I also noticed that the fuel gauge doesn't work now. I guess it is straight forward enough to say that I got a bad Fuel Tank Selector Valve but is there anything else that I need to do or check before I perform this swap??

[100%Chevy]

Check the 10 amp fuse in the fuse block!
Mike.

[SilveradoDude]

Originally Posted by 100%Chevy

Check the 10 amp fuse in the fuse block!
Mike.

Which 10 amp fuse?

[100%Chevy]

Lower left side of the fuse panel.
It feeds power to the left vertical bus bar on the panel.This is for accessories
Your tank switch gets it's power from this bus bar.It's usually plugged in at the top left.
Or.you could just check all the yellow 10 amp fuses!LOL!
Next,you could make sure the harness plug is all the way in at the valve.
when the valve loses power,it will stop in whatever position it happens to be in.
sometimes it stops in between tanks,giving you no guage and no tank=no fuel at all!
Valve may be just stuck too.
Mike.

[hatzie]

The fuse won't stop the fuel flow and it won't stop the gauge from working.
Since the fuel gauge stopped working I'm going to assume your truck was made in 1981 or later.

Check and make sure the plug is seated all the way into the valve. I usually wipe some SilGlyde on the Weatherpak plug seal to keep out water and make it easier to seat. Silicone grease doesn't eat soft rubber and synthetic compounds like petroleum based greases.

Here's my thread on the 73-91 RPO NL2 dual tanks http://67-72chevytrucks.com/vboard/73-87 (91) Dual fuel tanks theory of operation
Post #1 is the 73-80 systems
Post #2 is the 81-91 systems

[SilveradoDude]

Parked the truck in the garage last night to get caught up on a few items, one of them was the fuel selector valve. After I finished replacing the valve (which was a real pain), I tried to start the truck but it wouldn't start. No fuel.

I put the old valve back and it started just fine. Also, it ran fine without the plug even plugged into the valve. The primary problem that I had (which I still have) is that the it only pulls fuel from the passenger side tank, I can't change to the driver side tank. The gauge works fine.

I still need to fix the original problem.

[hatzie]

The motorized valve doesn't change position til you put the correct polarity on E & F of the plug to turn the motor. A new valve shuttle could be anywhere in its' travel but the gauge should remain on one side or the other til the shuttle reaches the end of it's travel.

Usually the $13 polarity reversing dash switch is the problem with the 81-91 systems. Use the AC Delco D7809C 87-91 RV series switch. The 81-86 CK series switch isn't as reliable. https://www.amazon.com/ACDelco-D7089.../dp/B000EQU15Y

I would test that the RED and BLACK wires on the switch plug have juice.
The ground runs to the buss bar over the E-brake.
The Hot runs to an Ignition power accessory plug in the front of the fuse panel. If you look in the wiring diagrams it'll show where the fuse is and which position the factory put the NL2 harness power plug into.

[SilveradoDude]

Originally Posted by hatzie

The motorized valve doesn't change position til you put the correct polarity on E & F of the plug to turn the motor. A new valve shuttle could be anywhere in its' travel but the gauge should remain on one side or the other til the shuttle reaches the end of it's travel.

Usually the $13 polarity reversing dash switch is the problem with the 81-91 systems. Use the AC Delco D7809C 87-91 RV series switch. The 81-86 CK series switch isn't as reliable. https://www.amazon.com/ACDelco-D7089.../dp/B000EQU15Y

I would test that the RED and BLACK wires on the switch plug have juice.
The ground runs to the buss bar over the E-brake.
The Hot runs to an Ignition power accessory plug in the front of the fuse panel. If you look in the wiring diagrams it'll show where the fuse is and which position the factory put the NL2 harness power plug into.

Hey man I bought that switch and tried to install it and it would not budge. Took a look at the prongs and one of the four has a "hump" that makes it impossible to fit it on the harness plug...what gives??

[hatzie]

It's a locator to key the connector. Not sure why the additional key was necessary. The locking wings and blocked off terminals of what would normally be a six terminal connector are pretty darn effective.
The 81-86 & 87-91 trucks use the same connector 12004101. There is another similar connector 12004139 with a differently placed locator notch.
Look at the connector and you'll see a notch toward the center for the locator. The 12004139 connector was used on some of the 89, 90, & 91 RV trucks. Apparently Delco is only making one TBI style switch now and we have to deal with it.

The 12004139 connector looks like this. Notice the additional notch toward the centre on the corner socket. The more common 12004101 has the notch in the centre terminal on the same side.



It's not the end of the world. That switch will still work just fine you just have some extra work to fit the switch.

If your switch is setup for the 12004139 connector You'll need to extract the terminal from the connector shell and make a notch in the plastic to mate with the odd locator bump then re-install the terminal. You can do it with a small saw file. I have done it to make an oddball switch work and it works just fine. I didn't know at the time why the switch I got was slightly different and I bought some after that had the old locator bump. One benefit is you can use a switch with either locator when it's done.

[SilveradoDude]

Originally Posted by hatzie

It's not the end of the world. That switch will still work just fine you just have some extra work to fit the switch.

Not the end of the world, but before you recommend someone buy a replacement part that is not a direct OEM fit you should warn them that modifications are involved. it is a bit of a pain to pull those wires out of the harness, modify the plug, then re-install. Not to mention that plug is not even available. Bottom line it is not plug and play.

[Nickelcharlie]

Ol post deleted

[hatzie]

Originally Posted by SilveradoDude

Not the end of the world, but before you recommend someone buy a replacement part that is not a direct OEM fit you should warn them that modifications are involved. it is a bit of a pain to pull those wires out of the harness, modify the plug, then re-install. Not to mention that plug is not even available. Bottom line it is not plug and play.

It was hit or miss. Out of a dozen switches I've used there was one very recently that was setup for the odd connector. The other switches didn't have a locator at all.
You extract one terminal and modify the plastic shell and reinstall that terminal. The NL2 wiring is not wrapped up in the cab harness its completely separate.

[AustinBelair]

Originally Posted by hatzie

It was hit or miss. Out of a dozen switches I've used there was one very recently that was setup for the odd connector. The other switches didn't have a locator at all.
You extract one terminal and modify the plastic shell and reinstall that terminal. The NL2 wiring is not wrapped up in the cab harness its completely separate.

@Hatzie

I just ordered that switch. Maybe that is the issue with mine too that you were helping me with.

[Nickelcharlie]

Didn't real size this was an old post