Fuel system question

[XGoldman]

Another newbie question.....





Do our 1st Gen. fuel systems send unused fuel back to the tank like the others do?



Thanks,

David

 

[BushWakr - RIP]

WELCOME



The answer to your question is yes, they do have a return fuel line. In fact that return fuel is the one and only source of injector pump cooling on the 1st Gen trucks.

So, that is one reason why many people use a fuel additive to atleast help with lubricity (pump lubrication).

If you look at your injectors, you'll see the main (larger) line leading to the injector, attached by a nut.

On the side of the injector you'll see a funny little 'screw' with a single (smaller) line connecting them all together. That is the return fuel line.

This sends the fuel back through the inj. pump and on its way to the tank, it cools the pump as it goes.



Any help??



Bob.

 

[XGoldman]

Thanks for the answer it help alot.



I just pulled the(long neglected and unused) aux. fuel tanks off my"new" truck for refurbishing and found that when they were installed there was no fuel return line. Since I need to replace the fuel lines anyway now I think that I will raise the bed just to see how they plumbed everything. I'm betting that the return line just dumps back into the main tank which means that If I use the aux tanks that I will have to use a quarter +\- of the main tank before using the auxilliary tanks to avoid spreading fuel everywhere.

 

[Power Wagon]

The flow through your fuel pump and injectors that's returned back to the tank is enough to empty your tank and overfill the other quite rapidly. It's on the order of a gallon every 2-4 minutes, if memory serves.



You can get tank switches that switch the return fuel back to the tank it came from. Also, if you don't have any means of putting a return into the tank directly, you can "Tee" it into the filler vent, which runs back to the tank. That is, however, a very poor substitute, since it will allow your fuel system to siphon itself dry after being parked for a while (how long? I don't know. Could be minutes, hours, or days - maybe never, if your supply pump has positive sealing check valves) The return should go back to below the fuel level to prevent this "siphon" problem.



Just FYI, to help you decide how to deal with it...

 

[JLEONARD]

Another way to prevent siphoning back if you T into the filler vent is to install a 1 to 2 psi check valve...

That is commonly done in the marine applications , mostly re-powers, when the return doesn't go to the bottom of the tank.

 

[XGoldman]

Well guys, I removed the bed from the truck and checked out how the aux tanks were plumbed. Just as I thought, there is/was no return line going to the saddle tanks. The only way that I can figure that the system worked is this:



All three tanks(30gal factory, 16gal aux, 14gal aux) have sending units in them.



You run the main down to 1/4 tank (+/-) then switch to one of the aux tanks and monitor its fuel level as the lift pump empties it and the injector pump dumps the return into the main tank. When the aux tank gets near empty, switch back to the main and run it down to 1/4 tank then repeat the process with the other aux tank.



Any other ideas?



Also any idea where I can get a couple of filler necks for the auxilliary tanks. They use a neck that is approx. 6-8" long (welded into the filler tube) and use a "standard gas cap",not a threaded one like our factory tanks.