Fuel Rail Set-up on a 4.0 swap

[JeepinMaxx]

I swapped a 4.0L in my 90YJ a while back. On the fuel rail - there is a 5/16" 'return' line coming off the rail - where is that supposed to go? My carbed engine ran that back to the tank. So I assumed that's where it should go. Am I wrong? I was checking out the MPI conversion instructions and they mentioned that the 'return hard line' would no longer be used. Now i'm worried I have it hooked up wrong ( the YJ has run 2+ years like this) BUT, if I stall- it has trouble starting back up (feels like a flooded carb used to) Also - when I'm on a low tank - when I pop the cap to fuel up - it's under pressure. Looking for some input...

 

[beaker]

Yes, the rail should have a return to the tank. Usually an EFI conversion will add a line as the carb return lines are usually too small.

 

[toyworx]

I'll look at my MPI today and get back to ya.

 

[jon]

yeah return line should go back to the tank as said.

The stock line from the 4.2l is more than adequate as they continued to use the same size when they went to the 4.0

Is your tank under pressure or vacuum. mine give me a slight hiss every time i open it, but its a vacuum

Does it have problems restarting hot or only whne you stall it? are you stalling it or is it stalling on its own?

 

[JeepinMaxx]

Thanks for your input

It's only hard to restart if it stalls while hot
by stalling I mean while idling up a rock. If it stalls and I try to use the starter to get me over the rock - it has trouble startiing.

No load it idles all day just fine.

Also when I shut off the engine hot (with the key) it starts right back up - no problem.

Gas tank is under pressure when I pull the cap on an near empty tank on a hot day. I assume this pressure should be released by the tank vent?

 

[toyworx]

My MPI has a return going to the tank.

 

[jon]

thats because the pressure regulator is back by the tank .