2nd Gen Non-Engine/Transmission fuel lines

[Tractorat]

OK, so Ive seen a lot of ref to folks putting in 1/2 inch fuel lines. Please forgive my lack of knowledge, but just what is the benefit of a 1/2 fuel line over stock (assuming clean fuel) ?

Thanks

 

[Tmar04]

More volume of fuel delivered to vp44 it would seem to me, assuming pump was ok???

 

[JR]

The OEM lines are sufficient to allow enough fuel to flow to the VP in a stock engine but that is about it. Even in stock form they are restrictive and limit the volume of fuel which is important for proper cooling. The more you modify the truck the more deficient the lines become. This is evident if you have a fuel pressure gauge as the pressure drops substantially under load. If your lift pump is mounted on the side of the engine it is even harder on the lift pump as the pump has to draw fuel through such a small opening over the length of the truck. Pumps require larger suction lines than the discharge to perform satisfactorily, not to mention the shorter the run the better. The best thing you can do regardless of which lp you own is relocate the pump to the frame rail and install larger lines. This puts the lift pump in a "pusher" position as pumps are designed to be, while providing enough fuel to cool the VP.

3/8" fuel line is adequate for most engines but the price difference between 3/8 and 1/2" is minimal which is why most opt to go with 1/2".

 

[Tmar04]

Thank you so much. I have intank pump that gives me 13 at idle, then drops to 7 if you really get on it. Don't know about WOT. Never done it. Seems to recover quickly after acceleration to 12 lbs normal cruising at 50-60 mph, not towing. Just wondered if installing 1/2 in line from filter to tank would help.

 

[KATOOM]

1/2" lines add more volume to the main line which in turn allows for the fuel pump to work less having to supply the overall volume consumed by the engine. Granted, there's always fuel moving through the lines as various excess fuel exits the overflow but nonetheless, the more fuel in the line the less the fuel pump has to immediately supply during demand. This is why overall fuel pressures will increase when larger diameter supply lines are installed. Aside from that, the stock banjo fittings are terribly restrictive and only add to the problem and should be replaced. The best is JIC fittings and no less that 3/8" supply. The return is of no concern and will flow enough.

 

[Tractorat]

Thx. I had an issue with air getting into the fuel line from the tank causing a loss of pressure. When I got that fixed I also had a fp gauge installed. I thought I noticed a performance improvement which started me wondering about the bigger fuel lines.

 

[Tmar04]

Thanks so much,Katoom. It seems I'm on the right track. The 1/2 inch line from filter cannister to supply line of intank oem pump should help a little. I will replace the banjo fitting on inlet of fuel cannister with metric adapter and jic fitting from Vulcan performance, as I did on big line kit from cannister to vp44
again, my thanks for your expertise.

 

[KATOOM]

You're welcome.

 

[SAndreasen]

Thank you so much. I have intank pump that gives me 13 at idle, then drops to 7 if you really get on it. Don't know about WOT. Never done it. Seems to recover quickly after acceleration to 12 lbs normal cruising at 50-60 mph, not towing. Just wondered if installing 1/2 in line from filter to tank would help.

I have an in tank pump feeding a fass direct replacement pump mounted to the side of the block in stock location thus the the name fass ddrp I see 16 idle and 6 wide open at 3200 rpm under load or empty truck