Converting to run fuel return

[Lee H]

I am about to embark on the mission of transferring my 3SGTE from my mk1.5 to my roadster. I know it's not a common conversion but I have ordered the mounts so no going back now.

Just want to make sure I have everything covered before I start and one thing I haven't been able to find info or pictures on is how to run a fuel return back to the tank.

Has anyone got any pictures or a guide? I have read about using the original feed as a return and connecting my uprated pump to a new feed but I am unsure how this will work as not sure if it would drain back to tank ok as that's not what the original feed was designed to do etc.

Any advice on the best way to tackle this?

Thanks,

Lee

[NoobieMRS]

Lee,

I would delete the canister. I assumed you are swapping a gen2/3. From the looks of the gen4 (iirc) they do incorporate an evap system. Any other gen doesn't therefore you could just delete. Upgrade fuel pump, add a return line, delete all evap sensors, cap everything and add a breather somewhere in the system.

Here's what Paul Woods had to say about my system. Kind of the same way many spyder has been doing really.

What are you using for Evap then? I don't see any breather system on your tank? If you don't provide a way for it to breathe it will vapour lock (suck itself into vacuum).

I don't really understand the whole thing but take it for whats it's worth. I'm redoing it this winter.

I ran a breather here in red. Maybe not the best place. I should had blew in or suck the opening to see if there is anything blocking it because it didn't work too well. Works fine but I have to pump gas sloooow.



I would put a breather here instead. And block off ^.


You could leave the evap in place. If you blow in the hose, it has a one way valve that doesn't take a lot of pressure to open it. I might run a line to one of these bolted somewhere and just delete the canister (that huge black box).

[Paul Woods]

The easiest way is to use the current tank Evap line as a return, but it isn't a simple matter of just hooking up to that line, it has too small an internal bore for fuel return, so small that it will artificially raise the fuel pressure as it struggles to get back to the tank.... not good.

Remove the pump assembly and drill the evap fitting out to 6mm bore and gut the flap inside so the fuel has no restriction, you can now use that line as a safe return.

For Evap i put a T piece into the fuel tank overflow line and run a vac line to a charcoal cannister for that.

[Lee H]

If I wanted to delete the evap canister and evap system completely (don't see any benefit of keeping it with a 3SGTE) how would I go about this?

I would use the evap line as a return as per Paul above and use the original feed but I assume there will be a fair few more pipes and breathers on top of the tank.

Also what happens to the standard fuel pressure regulator which I assume is in the pump assembly somewhere?

[Paul Woods]

You can't delete it or the tank will vapour lock, you would need to let it breathe to atmosphere somewhere, which is going to be fumey.

Another way is to leave the EVAP side alone, and make a T piece on the fuel filler overflow line, plumb your return in there.

[Lee H]

Ok. Was hoping to get rid of the big canister in the engine bay but never mind.

As I'm having to keep the 1ZZ ecu will this still control the evap system or does it not matter?

[cdwood2010]

On the 3VZ swaps I dump the purge, and divert the breather pipe into the corner of the engine bay on a Mk2, terminating the pipe in the small plastic cup thing.

Can't say I've noticed it being overly whiffy.

C.

[Paul Woods]

Chris from a safety point of view i cannot advocate the venting of petrol fumes into an engine bay for obvious reasons, even if the chances of that igniting are extremely slim, if it did happen it could potentially have serious implications for both myself and the owner.

Back in the real world there is litte to no chance of that happening, but you can see the issue advising otherwise.

For 100% safety i eliminate the EVAP VSV control and run its purge line to the new engines intake somewhere so it's pulling vapours permanently.

[cdwood2010]

Very good point. I keep forgetting my willingness to bodge is sometimes a little crude.

I do like the idea of venting directly into the intake......

c.