Fuel tanks running out

[Obwonkonobe]

Ive got dual tanks, 2 16 gallons, they work fine, i put them in myself with new sending units and a new mechanical fuel pump, and a new filter. I have them wired to a switch under the dash that just controls the gauge and switching valve solanoid thing. But whenever I run out if gas in a tank it takes forever to pump back up, and I have another issue. Every time i run out of gas and go to the other tank to crank. During the crank when i go to pump fuel, it'll take power away from the switch running me back to the empty tank, and just pumps air. So my first question, where can i grab power that's always on when I have the key in AND when i go to crank.

Second, today i had a quarter tank and was backing into an incline, putting the tail in the air and the nose down, nothing major, just a weird angled parking lot. But then it died and started pumping air into the line. I put a gallon in the tank, still on the incline and nothing, is that normal with these trucks? It wasn't at all much of an angle, seems like a quarter tank on the sender would be plenty to keeo a good level. If it is normal tho is there any way to help the tank not dry out so easy?

The truck has left me stranded much more than id like to admit.. And its always because I've pumped air into the line, thanks

 

[Dutch Rutter]

For your power need you should be able to run it off the ignition wire which will give you constant power when the key is turned to on. If that still doesn't keep constant during cranking then you could run a constant hot from your battery but that could also cause a constant drain on the battery. Could there be a problem with the switch itself?

I'm guessing your truck did not originally come with the dual tanks? I only ask because mine did and I have not had a single issue with any of it. It always switches quickly. I can run a tank empty while driving, switch to the other when I notice a slight loss or sputter then it immediately picks up without any fuss.

Second, today i had a quarter tank and was backing into an incline, putting the tail in the air and the nose down, nothing major, just a weird angled parking lot. But then it died and started pumping air into the line. I put a gallon in the tank, still on the incline and nothing, is that normal with these trucks? It wasn't at all much of an angle, seems like a quarter tank on the sender would be plenty to keeo a good level. If it is normal tho is there any way to help the tank not dry out so easy?

This part also doesn't seem right to me. Yes the fuel will roll forwards/back and side to side since we don't have any kind of bladder in our tanks, you might be able to add one but I'm not sure about that, but once again I at least have never had a problem. Sorry I cant be of more help. I'm sure someone will chime in though.

 

[1987 GMC Jimmy]

Have you replaced the rubber lines? You’ll usually find “sucking air” and “cracked lines” in the same sentence.

 

[Honky Kong jr]

Blazer tank.

 

[Obwonkonobe]

I've replaced most of the rubber, but I don't get any bubbles in the filter when its running normal, just one at the top that's always there, I've heard that blaser tanks are great, but my bed had dual fuel doors and I really like having the reserve, I suppose if it never works tho I might as well blaser swap it. il try out the ignition wire, but I don't wanna risk draining my battery. I did pull the switch from a yard. its meant for a return line set up and has a weird vent on it, looks like a tube. but I hear the solenoid click really strong and I sucked through it before I installed it to test it, I trust it.

 

[Dougnsalem]

I've replaced most of the rubber, but I don't get any bubbles in the filter when its running normal, just one at the top that's always there, I've heard that blaser tanks are great, but my bed had dual fuel doors and I really like having the reserve, I suppose if it never works tho I might as well blaser swap it. il try out the ignition wire, but I don't wanna risk draining my battery. I did pull the switch from a yard. its meant for a return line set up and has a weird vent on it, looks like a tube. but I hear the solenoid click really strong and I sucked through it before I installed it to test it, I trust it.

Yeah, that's the one I need. I snapped off a nipple. How much was it? New I think they were 63.00?

 

[Obwonkonobe]

Yeah, that's the one I need. I snapped off a nipple. How much was it? New I think they were 63.00?

mIi not sure how much that yard would've wanted, after they charged me 20 bucks for a rim that won't hold air after they swore it would, I just started filling my tool bag. a good way to test them in the yard tho is to just rip one out and connect it to your battery, they're fairly simple

 

[RustyPile]

Ive got dual tanks, 2 16 gallons, they work fine, i put them in myself with new sending units and a new mechanical fuel pump, and a new filter. I have them wired to a switch under the dash that just controls the gauge and switching valve solanoid thing. But whenever I run out if gas in a tank it takes forever to pump back up, and I have another issue. Every time i run out of gas and go to the other tank to crank. During the crank when i go to pump fuel, it'll take power away from the switch running me back to the empty tank, and just pumps air. So my first question, where can i grab power that's always on when I have the key in AND when i go to crank.

Second, today i had a quarter tank and was backing into an incline, putting the tail in the air and the nose down, nothing major, just a weird angled parking lot. But then it died and started pumping air into the line. I put a gallon in the tank, still on the incline and nothing, is that normal with these trucks? It wasn't at all much of an angle, seems like a quarter tank on the sender would be plenty to keeo a good level. If it is normal tho is there any way to help the tank not dry out so easy?

The truck has left me stranded much more than id like to admit.. And its always because I've pumped air into the line, thanks

In addition to leaky fuel lines, you've got the selector valve wired wrong.. It's not a solenoid that needs constant power.. The selector valve is actually a spool valve. The "electric part" is an ungrounded DC motor that moves the spool valve. The switch is wired in such a way that polarity is reversed back and forth to make motor change rotation direction. Once the motor has moved the spool valve, voltage is not needed to "hold" the valve. Momentary voltage application is all that's needed. The factory control switch in the dash has 2 parts.. One part of the switch selects the proper tank gauge sending unit.. The other parts applies the voltage momentarily to the selector valve.. The wiring for dual tanks is complex but not difficult to add/construct once you understand how the system works..

 

[Obwonkonobe]

In addition to leaky fuel lines, you've got the selector valve wired wrong.. It's not a solenoid that needs constant power.. The selector valve is actually a spool valve. The "electric part" is an ungrounded DC motor that moves the spool valve. The switch is wired in such a way that polarity is reversed back and forth to make motor change rotation direction. Once the motor has moved the spool valve, voltage is not needed to "hold" the valve. Momentary voltage application is all that's needed. The factory control switch in the dash has 2 parts.. One part of the switch selects the proper tank gauge sending unit.. The other parts applies the voltage momentarily to the selector valve.. The wiring for dual tanks is complex but not difficult to add/construct once you understand how the system works..

So i only need momentary power to switch? Good information thanks

 

[Paladin]

Have you replaced the rubber lines? You’ll usually find “sucking air” and “cracked lines” in the same sentence.

X2

 

[78C10BigTen]

Yeah, that's the one I need. I snapped off a nipple. How much was it? New I think they were 63.00?

My switch valve also does not work but when i saw it costs upwards of $70 i figured F that i dont need them both to work right now and have had no luck finding them in a yard.

 

[Honky Kong jr]

In addition to leaky fuel lines, you've got the selector valve wired wrong.. It's not a solenoid that needs constant power.. The selector valve is actually a spool valve. The "electric part" is an ungrounded DC motor that moves the spool valve. The switch is wired in such a way that polarity is reversed back and forth to make motor change rotation direction. Once the motor has moved the spool valve, voltage is not needed to "hold" the valve. Momentary voltage application is all that's needed. The factory control switch in the dash has 2 parts.. One part of the switch selects the proper tank gauge sending unit.. The other parts applies the voltage momentarily to the selector valve.. The wiring for dual tanks is complex but not difficult to add/construct once you understand how the system works..

Hence depress switch fully printed on the switch?

 

[RustyPile]

So i only need momentary power to switch? Good information thanks

Not exactly correct.. You need full power to a momentary switch that only momentarily applies power to the valve.. And that switch needs the capability of reversing polarity to the motor on the valve.. Just like on power windows.. The motor is not grounded directly.. The motor turns one direction to raise the window.. Reverse the polarity ["toggle" the switch the other way] and the motor turns the other direction and lowers the window...

 

[Obwonkonobe]

Not exactly correct.. You need full power to a momentary switch that only momentarily applies power to the valve.. And that switch needs the capability of reversing polarity to the motor on the valve.. Just like on power windows.. The motor is not grounded directly.. The motor turns one direction to raise the window.. Reverse the polarity ["toggle" the switch the other way] and the motor turns the other direction and lowers the window...

But there's only one wire for the fuel selector valve.. Its grounded to the frame

 

[RustyPile]

But there's only one wire for the fuel selector valve.. Its grounded to the frame

Not sure what you have going on.. My valve looks like this one and has six [6] wires..
https://www.summitracing.com/parts/...MI3-fUl8qS2QIVBR6GCh1meQ15EAQYAiABEgKxU_D_BwE