Plastic fuel lines and metal fuel line run my 1974

[lunarkingdom]

I have a clear and light blue set of fuel lines running along the passenger side inner rocker panel of my 1974 2002 and I also seem to have a metal line going under the bottom of the drivers side. My question is which are for what, assuming the white and blue plastic lines are the send and return for fuel from the tank and might go through a plastic tank under the place where speakers go in the back window. Is the extra hard line on the drivers side already plumbed for fuel delivery? I had a scooter accident and can not check it at the moment but I did rip out the plastic lines they were in the way of repairing my floorboard so I am wondering if I need to replace them or if I can get away with the one hard line. Thanks!

[Mark92131]

One runs from the vapor canister under the parcel shelf in the trunk up to the Carbon Canister in the engine bay, "Blue?".  The other is the self-sealing feed line for gas to your carb, "Clear?".  The hard line on the driver's side is the return line back to the tank.  Some people use the hard line to feed their EFI conversions.

 

@John76 will provide one of his spectacular drawings so you can put it back together.

 

Mark92131

Edited January 4 by Mark92131

[lunarkingdom]

1 hour ago, Mark92131 said:

One runs from the vapor canister under the parcel shelf in the trunk up to the Carbon Canister in the engine bay, "Blue?".  The other is the self-sealing feed line for gas to your carb, "Clear?".  The hard line on the driver's side is the return line back to the tank. 

This year car 1974 is exempt from smog in my state so if I wanted to I could use the hard line for main fuel to the carb if I wanted to? I will be deleting the carbon canister and or the vapor canister if they are still there.

[Son of Marty]

You can run the metal return line for fuel delivery with just minor plumbing if the return line has been left open on either end be sure to flush it out before using it and inspect it for rust specially around the sheet metal tabs that hold it in place. 

[John76]

2 hours ago, lunarkingdom said:

I have a clear and light blue set of fuel lines running along the passenger side inner rocker panel of my 1974 2002 and I also seem to have a metal line going under the bottom of the drivers side.

Here's a sketch of the fuel/evap. system in your car.

The clear plastic line is the fuel supply line for the mechanical fuel pump.

The blue plastic line is the vent line for the fuel tank. Also sends fumes from the vapor tank to the charcoal canister where it is sucked into the intake manifold through the spigot directly beneath the carb (not the ported vac. spigot on the carb).

The steel line running underneath the left side of the car is the fuel return line for carb cars, or the fuel supply line for the Tii or cars with electric (pusher) pumps mounted near the fuel tank.

John

PS: I just posted a new sketch on the electric fuel pump installation using an inertia switch.

See the latest post "Fuel Lines for Side Draft Webers",

 

 

[lunarkingdom]

15 minutes ago, John76 said:

The steel line running underneath the left side of the car is the fuel return line for carb cars, or the fuel supply line for the Tii or cars with electric (pusher) pumps mounted near the fuel tank.

Ahhhh! I currently have a fuel pump bolted to the head, your post helps me figure out that I need a pump in the rear. I think I might have forgot to mention previously that when I replaced the floor pans I ripped out the blue and clear plastic lines as they were both broken in a few places anyway.

Now I need to source a rear fuel pump (with pressure sensing turn off?) so I wonder what is the best one to use?

I also need to source a plate/gasket/bolts to cap off the hole in my head for the old cam driven pump.

I think I read recently that an e-30 in tank fuel pump is the way to go but my memory is fuzzy.

[Mark92131]

The fuel return valve directs fuel back to the tank when the engine is turned off and there is no manifold vacuum.  This is helps prevent vapor lock in the carb on those hot summer days in California.  The clear plastic fuel line is designed to self seal in a fire, preventing gasoline from leaking in the passenger compartment and feeding the flames.

 

But bypassing these to use the metal fuel line is a workable solution.

 

8 minutes ago, lunarkingdom said:

Now I need to source a rear fuel pump (with pressure sensing turn off?) so I wonder what is the best one to use?

 

No need for another pump, just connect the mechanical fuel inlet to the steel line, plug the fuel return inlet at the tank, and connect the other end of the steel line to the gas feed on the tank's fuel sender.  Then figure out how to vent the tank.

 

8 minutes ago, lunarkingdom said:

I think I read recently that an e-30 in tank fuel pump is the way to go but my memory is fuzzy.

 

The E30 fuel pump is great for EFI, no so much for carbs, fuel pressure too high.

 

Mark92131

Edited January 4 by Mark92131

[Son of Marty]

The plastic fuel line is still available and the set up BMW used has served well for some 50 years. The one problem with the steel return line is it runs just inside of the rocker panel and could break in a "t bone" collision.

[lunarkingdom]

18 hours ago, Son of Marty said:

The one problem with the steel return line is it runs just inside of the rocker panel and could break in a "t bone" collision.

If the information Mark gave me a couple of posts ago is true and I can still use my cam pump to move fuel from the gas tank to the engine then if there was ever a break in the fuel line behind that pump and the pump kept pumping it would evacuate the line instead of evacuating the tank of gas like a rear mounted pump would. I am speculating and would love to hear if I am incorrect for sure. I do not want an unsafe car but I also would like to avoid having to run the blue and clear plastic lines again if possible. If the metal line ends up being rusty or damaged I would rather put a new metal line as most if not all of my classic cars had a single hard line to the motor from the tank.

Edited January 5 by lunarkingdom

[OldRoller]

If you have a carbed engine the metal line will work fine. No need for a return line. The condition of the metal line should be checked thoroughly for rust/cracks/etc. Plug one end and apply a hand-held vacuum pump to the other end, make sure it holds vacuum for 30 minutes. And inspect all clips and contact points for wear and rust. An isolator under the carb will help with any vapor lock, and the needle/seat of your float will need to be 100% of course, and a filter between your pump and carb.

 

[John76]

5 hours ago, lunarkingdom said:

pump kept pumping it would evacuate the line instead of evacuating the tank of gas like a rear mounted pump would.

Yes, it would evacuate the line from the break to the mechanical pump ... but the tank would be siphoned dry at the beak point...creating a pool of fuel at the T-bone site! ☹️

An electric pump mounted near the fuel tank and equipped with an inertia switch would solve this problem. ☺️

Before you rip out your damaged plastic supply and vent lines, consider using them as a convenient conduit from the engine bay to the trunk for your new fuel pump wires.

John

[lunarkingdom]

1 hour ago, John76 said:

Before you rip out your damaged plastic supply and vent lines

I posted that I already ripped them out as they were damaged so I missed the opportunity to do this.