fuel lines

hi, can anyone remember a thread that covered fuel lines/ pumps set up for fuel injection. i am sure it in here somewhere but i cant find it. had pics and ideas on where to put them and returns in to the vw fuel tank etc. thanks greg

8mm steel pipes from a brake shop $30 and just put return line into the filler neck. Holden commodore fuel pump $105

thanks ian, thats what i thought i just needed confirmation. so i am assuming i can use the original fuel line for the return even tho its smaller dia than the one i fit. greg

grogy wrote:thanks ian, thats what i thought i just needed confirmation. so i am assuming i can use the original fuel line for the return even tho its smaller dia than the one i fit. greg

I probably wouldn't as any restriction in the return line could cause an increase in pressure in the fuel rails. In theory this should only happen if the amount of fuel flowing back to the tank is above the capacity of the return line....

Also, Whilst I have seen many people plumb the return back into the filler neck (and it works), most of the guys that do this for a living will tell you that the return should be back into the bottom of the tank. This is for two reasons: 1) Reduces the noise of the returned fuel 'falling' from the filler neck when the tank is near empty (yeah, I know - in most cars you couldn't hear it over the exhaust 😀 ) and 2) the returned fuel can be quite hot and will be more likely to be close to the temperature that it turns to vapour, therefore if you return the fuel to the bottom of the tank the returned fuel will cool when it mixes with the fuel in the tank, reducing vapours and potential fuel loss.

Just remember that the high pressure fuel pump must be mounted below the tank height this style of pump will self-destruct very quickly if they are made to 'suck' the fuel from the tank.

R 🙂

thanks ratty, i read somewhere, i can put a y junction into the same fitting as the outlet, have u heard if this is ok. thanks greg

grogy wrote:thanks ratty, i read somewhere, i can put a y junction into the same fitting as the outlet, have u heard if this is ok. thanks greg

I have heard of a T junction being used in the line between the tank and the pump. From what I have read and seen this does work, but there is some concern about the warmer returned fuel being repeatedly circulated through the fuel rails and becoming hotter with each pass, eventually causing the fuel to vaporise in the rails. I suppose that it would depend on how much cold fuel is being drawn in from the fuel tank at the same time....

Are you going to use an external fuel surge tank or in tank swirl pot as part of your fuel system?

R 🙂

This is how I configured my fuel system.

The excess fuel from the engine came back to the inlet side of the low pressure pump. The reason the return line goes into the filler neck is because welding fittings into the bottom of the tank caused me rust issues. Once you burn the paint off inside the tank you're screwed unless you do the whole POR tank restore thing. I didnt have any issues with fuel getting hot from recirculating.

Interesting.

Almost the same set-up as mine, except the return from the fuel rails/reg was connected directly back to the pot rather than to the input to the LP pump. Your system still allows the warm fuel/vapours/air to escape back to the tank if they need to. Where did you mount your pot?

R 🙂