Fuel line question

[ankarback]

My fuelpump broke down yesterday when I was out wheeling. A friend gave me a ride home so I could take the fuelpump from the blazer to replace the broken one on the sub. When I got back to the sub I discovered that that fuelpump had two fuellines from the tank but the "new" one from the blazer has only one.

I mounted it anyway just to see if it was going to work, since i had to get the truck home it was late, dark and raining and the sub ran just fine with just one fuelline connected. So the question is, what is the return fuel line for on a carburated truck? Seems like it's working fine without it.

 

[randy88k5]

Im pretty sure that is just the EVAP line, to collect the vapors from the tank and store them in the charcoal canitster. It would run fine without it, just might get some fuel smell. I have TBI, so Im not positive. Someone will chime in if Im incorrect.

 

[diesel4me]

3 hoses??

Im pretty sure that is just the EVAP line, to collect the vapors from the tank and store them in the charcoal canitster. It would run fine without it, just might get some fuel smell. I have TBI, so Im not positive. Someone will chime in if Im incorrect.

If it has 3 hoses,the smallest 3rd hose is a return line..fuel pumps on vans and vehicles with A/C often had those pumps..it recirculates fuel back to the tank constantly..keeps it cooler and helps prevent vapor locking in hot weather..you can block off that 3rd line and ignore it if your truck doesn't need it..the 86 305 motor from a van I put in my 79 C10 has a "3 hoser" on it,with the 3rd one plugged off with some hose and a bolt and 2 clamps..make sure its sealed good,you don't want gas spraying on the starter or spark plugs!

 

[ankarback]

I beleive the engine is from a van since it has the long oil dipstick, so that makes sence then. I make sure to plug the return line, right know I just put a screw in it as a plug. Tanks for the help !

I think I'm going to buy a new fuelpump to carry with me as a spare. The one from the Blazer is from -76 and I don't wan't this to happen again. You can have more fun than replacing a fuelpump in the rain with a flashlight at ten o'clock in the evening

 

[diesel4me]

Not fun!...

I've had them croak at bad times too,like during blizzards,or on the highway where its easy to get hit and killed trying to fix it on the spot..

..I now carry a universal electric fuel pump I found on a car I junked with me..it looks like a gas filter,with wires coming out of it..Parts stores sell them for about 20 bucks here..--

I hooked it to a 4' peice if extension cord and put two battery charger alligator clamps on the wires,and put a few feet of fuel line on each end of the pump,so if my fuel pump craps out all I have to do is splice in the electric one to the inlet and outlet hose or steel line on the dead pump,and clamp the wires to the battery..

Then I can still drive home,and change the pump at my conveinience..better than walking home,or getting run over trying to put one in on the side of the road..

 

[hack500]

iirc, something else to beware of on blocking the return line is that the fuel pressure bypass gets fed to the return line. you may get increase fuel pressure at the carb which may not be good with a q-jet.

and I don't know if it will be more likely to leak past the diaphram and put gas into the oil or not.

 

[diesel4me]

??????????

I don't know for sure..I do know I've plugged that 3rd line off on quite a few pumps and never had any oil dilution issues or flooding..I suppose anything is possible..in any case when this pump croaks I'm using the "normal" 40987 AC pump with only 2 hose connections,one in,one out..IF I still own the truck that is!... ..

I think AC pumps are the best (at least they were before they stopped making them in the USA)..I have a 73 "307" in my van--still has the original AC fuel pump on it!--so does my 86 305 motor in the 79 C10!..both have at least 100,000 miles on them..the 73 should have died of old age by now!..(32 years old! )..I really should have put a new one on the van BEFORE I put the motor in..its a beotch to change IN the van!..

 

[ankarback]

Actually, the Q-jet comes from my blazer too, and it runs a lot better now with the new fuelpump. It's just one fuel line to the carb so it can't be connected to the fuel return line.