Jump to content


EFI to Carb Conversion: Hose/Vent Questions

Recommended Posts

gonna swap out the efi in my '78 for some su's and i've been trying to figure out what i need to do for fuel line routing and venting. been through the fsm and can't find anything very detailed and there are so many pics of different ways to do it i'm scratching my head at this point...


the goal is to clean up my engine bay as much as possible, keep things simple and avoid heat on the fuel lines to reduce vapor lock, etc. so i figured i'd run new hard lines up the firewall and over the tunnel and re-locate the fuel filter by the brake booster and then send a line out to the carbs. this should keep the fuel cool and reduce the clutter going 'round the front of the valve cover. i've got a low-pressure fuel pump that i plan to mount out back in the same location as the oem efi pump.


questions for those who have the experience w/this:

  • do i need to keep the charcoal canister - if so, how do i plumb it? i don't even see it on the 240 - am i missing something?
  • if i delete the canister, do i just block off the third hard line that goes to it? will that cause expansion pressure issues in my tank?
  • any issue w/just deadheading to the carbs, or do i need a return to the tank?
  • i've read various conflicting reports on the return line - many site vapor lock but without the oem rail running over the headers is this an issue?
  • i could put a bleed-by fpr after the filter and run a return line to the tank, but i've read that fuel pressure regulators restrict flow and i don't want to drain my bowls... any wisdom on this?


thanks in advance for the help.

Link to post
Share on other sites

Hi Rossi,


The carbon canistor doesn't have anything to do with the EFI. It is part of the emmision control system introduced introduced in the 260Z. Maybe the late 240Z's with the flat top carbs had them as well, I not sure.


If you want to see how to plumb it for carbs. Download the 260Z manual from XenonS30.com and check it out.

It is simple. The canister has a purge valve with two tubes going to the inlet manifold.

The tube coming out the top of the purge valve goes to a Tee piece in the line to the distributor vacuum advance.

The second tube (slightly larger diameter) coming out the side of the purge valve goes to manifold vacuum.


I don't know what the government regulations say in your area, but it wouldn't hurt the enviroment if you left in on.

You will need to consider venting the tank if you remove it.


Fuel line: Im an EFI man. I have heard of people going for a return line and others just dead heading the system. If I did it, I think I would go for a return line to keep the fuel fresh, cool and reduce the risk of vapour lock.


Have you thought about how to run the pump? The fuel injection pump relay has some wiring to the ECU system for safety reasons.




Edited by EuroDat
Link to post
Share on other sites

I would not plumb the Fuel Filter by the brake booster. That's a high heat area. Could cause Vapor lock.


The factory placed the fuel filter on both EFI and carbed cars on the passenger side for good reason. Well away from exhaust heat. Follow the factory EFI fuel line routing for your carbs. You can actually keep the EFI fuel filter for the carb setup. Will work just fine and one less thing to change.


Change out the EFI electric pump for a carburated Electric pump that puts out less fuel pressure ( 4.5 to 7 psi ) . A Carter electric fuel pump is fine. Run an adjustable fuel pressure regulator that uses a Bypass system and retain the factory fuel return system.

Link to post
Share on other sites

Welcome to the darkside  :P


You will also need to rewire your fuel pump as well because the factory plug runs through the efi harness. I ran a return line and I'm not having any issues. Ive heard you can do it either way though. Good luck!

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...

Important Information

By using this site, you agree to our Terms of Use. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.