Rear gas tank drain issue 81 F150 Ranger

It seems that I'm always asking auto shop 101 questions. I can't run a syphon hose down the obvious fiiler tube, it bottoms out without getting wet. The rear tank drain hole has been filled by PO and told me to not use that tank. There's at least 5 gals of something in it. Manual says to syphon from the fuel pump which seems difficult and awkward. The 2 tank switch is much closer. Just wanting to repair the rear tank so it functions.
Ray again

The siphon hose is probably hanging up on the vent tube support at the tank inlet.
The tank fill is concentric to a center mounted vent.
Later trucks reversed this and fill down the center and vent around it. (much less burping)

Can you use a thinner or more flexible hose? It may be slower but it should reach.

I've never seen a drain in any of these tanks.
Perhaps the PO just ran a bolt into a rusty hole in the bottom of the tank?

Thank you. I'll use a smaller tube...

No matter what size tube (5/16 OD this time) , it goes in 26in and stops. I've done my fair share of remodel house wiring and I know about spinning the tube so that if the angle is off, turning the tube might help align better. It has maybe 5 gal in it

I'm thinking that the PO got something stuck in there. My siphon stops just where the filler hose bends into the top of the tank.
For such an easy access to the tank, I'm struggling to wrangle it out.  The weight of the old gas doesn't help

Perhaps they've got something stuck, but I'm telling you the ring that holds that vent tube is not going to budge.
I suppose you will see for certain when you get a look inside.

I'm sure the extra 30 lbs or so doesn't help, nor the sloshing around.
Be glad you don't have to pull one that is brimming full!  It's NO fun.

Please be careful.

I just replaced my saddle tank and vent tube is welded there. I can't imagine how hard it would be to remove a fill tank. Hopefully you had help. Just the thought of all that fuel...
Thanks for your help on this
Ray

When I installed my new 20gal rear tank, I made the rubber gas line maybe 10in longer than stock. It would give me more play room when wrestling the tank back in place. Would that cause a vacuum block in the line? It runs outta gas when I switch tanks. I haven't disconnected the line at the 2 tank switch yet to see if it flows, I'll do that in the morning. Just thinking I might have screwed up on that one
Ray

The tank vents through the rollover valve.
But if you made the fuel line 10in longer than stock it could  be folded somewhere up on top of the tank or pinched where it passes the crossmember.

The rear tank is a lot harder to see on top of than the mid-ship tank.
If you have one of those inexpensive fiber optic endoscope cameras for your cellphone, they are always good for peeking into small spaces like above the tank. (or inside a bellhousing, or behind a fuse box, or down inside a door at the window tracks, etc)

If you disconnect from the switch valve you might try blowing back through the line (into the tank) to see if it is obstructed.

Okay thanks for that. The gas hose seems loose up there but could be pinched . Was thinking the longer hose had a bigger volume of air in it and the fuel pump couldn't pull it. I'll get under there tomorrow n blow some air through the line.
Ray

You'll get it!  

Sometimes it's the little things that frustrate you.
Sometimes it's unexpected consequences.

The rubber gas line was nicely coiled on top o the tank (thanks to the endoscope camera) and gas came out at the tank switch connection.  Went for a drive and waited until I was going 60 and switched tanks, after a bit the engine stumbled a couple secs and then ran ok! So it's now "on line". Thanks for your help!
Ray

That's great news!  

Glad it didn't require pulling the tank down again.

please put a new tank in your near future to do list. but run that tank out of gas first. if the outside looks that bad and it already has one "drain " repair it should be replaced. leaking gas is too expensive and dangerous. maybe that's just the dad in me!

I replaced both tanks. Saddle was leaking and the rear was full of dark red liquid - rusty gas. Both are up and running. I did use the roofing membrane. Thanks for you input!
Ray

Mat, he just did..

Raywilson wrote

When I installed my new 20gal rear tank, ...

And good looking out for your progeny.
Hopefully your son will show his new engine a little more consideration.