'77 K20 Flexible Fuel Line Replacement

[ehjorten]

So...the '77 has been sitting for a while.  I went to start it up and put some heat into the engine and drive it around a little bit.  My son noticed that something was dripping under the Passenger's side!  I looked and it was fuel, so it didn't get driven!!

Turns out it was leaking from a 37 year old fuel line that was checked and cracked.  So...I figure I better just replace all of the 37 year old fuel lines that go between the 2 tanks, selector valve and forward hardlines.  The problem is that you cannot replace those lines without pulling the tanks!  Okay...so I pulled the tanks.

My questions are...my '77 seems to have 3-port sending units, but the one port is just capped off with a short section of flexible hose that has a metal cap inserted in the end.  What is that?  Can I re-create that?  The hose is pretty brittle just like the others.  Was that supposed to go somewhere?  Also...the passenger's side tank has always had an issue with filling.  It spews fuel out from between the metal filler neck and the rubber fill hose.  I have tried almost everything to get it to stop, but it won't.  Where can I get good replacement fill necks and formed hoses?

Thanks,

Erik

[Captkaos]

Vented tank port.  Should have a plastic piece in the end like your diff vent.
When you replace the lines, get some that are E85 safe.  It will cost you more now, but you won't be replacing them again in the future.

you can barely see it on mine here:

[ehjorten]

Interesting Capt!  I'm 99.9% sure this truck is completely un-molested and that the tanks have never been messed with.  The center port has a short length of hose with a formed sheetmetal plug in it.  All of the fuel lines have the original spring clamps in place and the selector valve appears to be original.

I will have to look that up in my parts and service books.

Another question...if I take the tanks and supports all apart and replace the fuel tank straps...what is the best way to install new straps?  I see new straps available, but don't see anything about replacing the original rivets that hold them onto the supports.  What is the best practice for that?

[ehjorten]

Nobody on the fuel tank strap replacment?  I've searched this site and the internet for what people are using to replace the factory rivets and have not found anything.  Everybody sells replacement straps, but nobody from what I can tell has anything posted about what they are using.

[ehjorten]

Did some searching on the 'net and it seems that the replacement straps may come with bolt and nuts to replace the rivets that you drill out.  Does that sound correct?

I was also wrong on the center fuel sender port...it just has a short length of 5/16" hose on it and it was just open to atmosphere!  Interesting!  Everything was stock!  Capt'n...you said that just has a standard diff vent on it?!

[bd]

Erik, do you still have the emissions vapor canister left of the radiator?

That 5/16" line should vent through the vapor canister via a steel tube that runs the right frame rail up to the front crossmember and over to the canister.

The tank straps can be mounted safely, using Grade 5 or better hardware.  But, I suggest using Grade 8 flanged frame bolts.

[Greybeard]

That's weird, either my memory is getting worse than I thought or my tanks are mounted different than yours. I didn't need to drill out anything just to replace the straps, one end has a t-fitting that goes in a slot and the other had the straight threaded rod. Maybe differences in years?
I have no real clue what year my frame is since it's got a government issued VIN number. Apparently someone lost the title, the truck was a stolen recovery, or something. It's not issued as a salvage title however. Anyway, if the tanks are sitting on shelves like mine are the straps are basically there just to keep them in position and not rattle. Seat belt fabric works good as an anti-rattle cushion.
Before going to the trouble of re-hanging those tanks you might want to go over them with a fine tooth comb. New sending unit gasket, peer inside to gauge the if they are rusty, maybe clean them up good and give the outside a good coating of rubberized undercoat. At worst a couple hundred dollars for two new tanks that will likely outlast the truck.

One more minor suggestion, if there would be any remote possibility at all that the truck might see deep water, run the tank vent, wherever you get it from up high and point the end down. I had everything on my old truck vented up to the cab interior to inside the space between the inner and outer roofs. In the A column works good also. But I took my truck into really deep water for it's stance. Ant water that gets inside anything however is bad water. Plumbers putty, silicone and plastic bags are your friends in deep water. So is 4" suction hose, duct tape, and a good fan belt adjustment. Nothing worse than blowing a belt because it's too tight under water. The major advantage is slippage though. These day's maybe those aluminum flex fans are better than used to be. They used to break at the first slap in the water. That was potential very bad.

[Captkaos]

Eric,
If yours has a Charcoal cannister it would vent to that as BD stated..
As for the straps, Did you drop the tanks like this:  http://forum.73-87chevytrucks.com/smforum/index.php?topic=9294.0
or did you remove the straps from the mounts?

[ehjorten]

Hey Capt'n!  I dropped the tanks the normal way...by unbolting them from the frame, but while I'm in there I am going to refurbish everything, paint the hangers, new anti-squeak, etc.  BTW...my '77 had no room to lower the tanks with the fuel lines attached.  I had to disconnect them from the selector valve, undo the clamp over the top of the frame rail and unbolt the ground strap from the top of the frame to get enough room to drop them enough to even attempt disconnecting the sender wire.

[Greybeard]

I've found that sometimes it's just easier to unbolt the front of the bed, and loosen the rear enough to lift the front so there is enough room for your arms in there. It only takes a few more inches. Just jack it or lift and slide a couple 2x's under the front mounts.

[ehjorten]

My replacement straps did not come with any bolts and nuts!  I have a friend that has an old rivet gun and bucking bars.  Going to borrow that and get some AN4418-9 rivets...should be fun!