The Stovebolt Site Forums The Shop Area Engine Shop Fuel line question

49 gmc 1 ton. Recently replaced tank and sending unit. Will be doing fuel line soon. Question I have is should I run 5/16 hard line from top of sender all the way to pump. Or should there be a rubber line used somewhere in between to account for any vibration or movement of cab?

Chevrolet truck - it looks like "yes"
GMC - most likely "yes"?

There should be rubber hose between any two major components that may move independently. If the tank is not mounted to the same frame that the tubing is mounted to, then rubber is needed. Rubber hose is used between the frame mounted tubing and the motor mounted fuel pump. It is also used to be able to remove certain items like gas tanks, filters and carb.

Thank you. Was kinda thinking the same way. Just wanted to double check. Thanks again. I will incorporate a rubber hose as a buffer.

A vibration loop is the old way - more expensive and difficult, more permanent.

A loop. As in coiling up extra tubing into a loop about halfway between?

I have to question your "more expensive and difficult" part. It's just an extra foot or two of tubing and eliminates a fitting, so really can't be more expensive, IMO. I guess it would be more expensive if you need to go out and buy a tubing bender.

Although the original installation used a short ( ~6") length of rubber hose.

It's not something you're likely to have on hand, nor can it be bought ready to use.

What's expensive or difficult about a little fine sand and a piece of pipe to bend the loop around?
Jerry

Have also had success using ice as well. Smaller pieces can go in the freezer. Larger projects need to wait for winter and go outside (at least for those of us living in colder climates). I suppose you could try cooling using some liquid with a low boiling point, too, if available. Some sources suggest mixing the water with soap. I have only used just plain water.

For 360 degree bends, like a vibration loop, this method might work better anyways as some tube benders don't lend themselves well to making bends much beyond 180 degrees.

One other consideration if you go the hose method is the hose interface. Do you have a way to form a bead in the tubing where the hose slips over the end of the tube? This helps keep the hose from being pulled off once the clamp is installed. I know this is probably not a line that will see much pressure, but it is still good practice.

Finally, in the spirit of "any-job-worth-doing-is-worth-over-doing", you could also silver braze an AN fitting on the end of the tube, then use a piece of braided line with screw on fittings. If visible, it would look pretty cool, too.

The fittings are available in different sizes, and are counterbored to accept the tubing. 5/16" is difficult to find sometimes, so you can just use a -4 tube to -6 adapter, and bore the -4 side it out to 5/16". I have used this method a lot for oil pressure and fuel lines - especially if they are stainless steel.


Best Regards...

A double flare tool for brake lines does a nice job of that. Just do the first step, and upset the end of the tube. I've done that for tranny cooler lines.

Practically speaking and in my experience, I've never see anyone coil a fuel line from a tank to the pump. including the factory. I have seen hundreds of short rubber hoses. If you put sand inside a fuel line for bending purposes, you would be considered a prime patient for the cuckoo's nest.

Spray carb cleaner and an air hose is just so far beyond the average wrench jockey's capabilities, right? I've made up hundreds of vibration loops on pressure gauge lines for industrial equipment using glass bead blaster media instead of sand to prevent the tubing from collapsing while forming the loop and never had a problem. Just clean the line thoroughly afterwards. Putting a flex line from the frame to the engine is a lot simpler way to deal with a fuel line, however.
Jerry

Mr. and Mrs. Stovebolt founders and editors: Please change my Avatar from "Master Gabster" to "Wrench Jockey" per above member request. I would be most satisfied with that name so as to stay in this great website you have created. This would not mean, however, that I would ever recommend putting sand in a fuel line.

Mr. Bartamos, you change your avatar title yourself. It's a profile option.

Gord
So you're a fish now? Or was that just a demonstration?

I am still trying to figure out where I am supposed to put a multiple coiled up section of fuel line under the cab floor so as not to create a tail hook for road debris.
Not that I want to get in the way of a healthy debate, or anything.
Carl
Well-renowned Preserver of Threads (except for the ones which I am sure I got killed)

It only takes a single coil of tubing to do the trick, and that can be oriented laying flat up against the cab floor. We're not talking something that's even as large in diameter as the frame depth.
But again, the original used a piece of hose coming off the fuel tank valve, and we all love a good debate.

Kevin: a wrasse is much nicer than a shark. They also like to hang around the wrecks in Truk Lagoon.

Back on topic. A hunk of rubber is all you need. Use coils for brake lines. Also for water temp gauge tube mainly to use up slack.

DoNe, ThAnK YoU

Hmmmm, wondering what you might know about the wrecks in truk lagoon

You got trees on your ranch?
Carl
Habitual thread locker

Palo Verde, Mesquite, Palm, Citrus, and others....problem is, they are only two foot tall. It's the desert ya know. It's tough down here. The winter lasted a week. Got down to +38 F in some places. Got a jacket on and made it thru.