Fuel lines at fuel tank: which is which?

[lostagain]

I am installing an electric priming pump at the fuel tank in my 5C. Just inside the fuel door. There are two copper lines side by side. The bigger one on the left looks to be 3/8" ID. The smaller one on the right looks like 1/4". I am assuming that the bigger one on the left is the supply, and the smaller one on the right is the return. In the engine compartment, the supply line is bigger than the return line.

Am I right?

Neither the maint. nor the parts manual are any help.

What would be a simple way to find out for sure? I have too many things apart right now to start the engine.

Somebody knows off hand?


JC

[bobofthenorth]

Just guessing but won't the return dump into the top of the tank?  If so you'll be able to easily blow into it and there will be head pressure on the suction line.

[lostagain]

Bob, are you saying that if I disconnect both lines at the tank and blow into the return line, fuel would come out the supply line? I could try that tomorrow. Also, if I blow into the supply line, I would have bubbles come up to the surface. The tank is full now, so it would be easy to see down the fill neck.

JC

[luvrbus]

It will be the 3/8 the fuel pump doesn't have a 1/4 suction line

[bobofthenorth]

No, what I meant was if you blow into a line that terminates at the bottom of the full tank there will be resistance whereas if you blow into one that is into the open top of the tank there won't be resistance.  Make sure you know where your check valve is though before you try this trick because you shouldn't be able to blow backwards through it.

[buswarrior]

Yes, bigger is supply.

happy coaching!
buswarrior

[lostagain]

Thanks guys for confirming what I suspected. I will double check by blowing into the lines tomorrow, thanks Bob. I will likely put the electric pump in line on the 3/8" one. I'll do a picture of the finished project.

JC

[Van]

John it's good to see the electric primer pump idea has your Shod Nod of approval  

 All the Best!
    Van

[boogiethecat]

Run the engine for a while and feel the lines... the return will be hotter

[lostagain]

Here it is. Simple installation, in line.

This is with the body panel back up. You can see the switch.

JC

[lostagain]

This one is with panel off. Just enough room for pump behind panel on the right.

JC  

[luvrbus]

Not going to work JC you left out the bypass I been told that for 20 years lol nice install

good luck

[Oonrahnjay]

    JC, is that a "pass through" pump?  I mean, if you don't have it switched on (in the prime mode), does the engine fuel pump just draw fuel through it -- like it's not there?  Would you mind posting where you got it, part number, etc.?   Thanks,  BH

[Van]

I agree with Clifford, not enough plumbing there to warrant several valves in the mix either LOL! Nope it'll never work!    Nice and simple, good job JC!

     Van

[bevans6]

Draw-through pump - yes.  works in-line while turned off - yes.  Primes the system in a jiffy (mine took 15 seconds for initial start-up on a new engine) - yes.

I put mine in the engine compartment, in the main fuel line going to the primary fuel filter.  It had no problem picking up fuel from the tank.

It is an Airtex E8131 External Fuel Pump, available many places, in different voltages, and rated for diesel fuel.  It is made in USA, fwiw.  http://www.airtexproducts.com/TSB/TSB-0108-01_ATX.pdf

This really should be a sticky.  Every time I post this I have to run out to the garage, get my spare pump, write down the number and google it to get the Airtex link.  At least this time I managed to find the picture without having to take a new one...     

Brian