Fuel return, early second gen EJ swap

[Gloyale]

So we just finished an EJ swap in my buddies GL. 81 model, originally a California Feedback carb 4wd model.

 

When I did the swap in my 84, I was able to use all the stock fuel lines (sans swapping to HP rubber)

 

But with this 81, the vent line coming out of the firewall spews gas at a pretty good rate. Haven't dug into the cab to see how that vent line i tied to the return line/tank.

 

Anyone have a Diagrham of the Fuel lines on an 81?

 

Anyone encountered this issue and solved it? Right now we just have that line capped and clamped.

[Numbchux]

not sure if/how it relates to the 81. but when I first did it in the '86, the gas tank would pressurize and spew a good amount of fuel out the vent line unless the gas cap was left open.

 

I don't really have an explanation or solution.....I just drove it for awhile with the line plugged and cap loose, and then un-plugged the line. and after a few hundred miles, I was able to tighten the gas cap with no issues. AFAIK, dhise hasn't had any problems with it since. I know he got 32mpg on the way back to detroit, so I don't think it was leaking anywhere

[GeneralDisorder]

As I recall - when Jerry (Bratsrus1) did the SPFI on his hatch (80 or 81) he ran a new fuel return line back to the tank.

 

Didn't your friend's car have the fuel pump in the engine bay?

 

I'll have a look at my '80 FSM and see what the deal is with the lines.

 

You may end up having to do a surge-tank setup where the carb pump fills the surge tank and the FI pump pulls from and returns to the surge tank.

 

GD

Edited March 22, 2010 by GeneralDisorder

[dhise]

I haven't had any trouble with it. The '86, even though it was carbed, must have some baffling in the tank because I have run it down to a gallon or two before filling up and there were no fuel issues.

 

 

 

not sure if/how it relates to the 81. but when I first did it in the '86, the gas tank would pressurize and spew a good amount of fuel out the vent line unless the gas cap was left open.

 

I don't really have an explanation or solution.....I just drove it for awhile with the line plugged and cap loose, and then un-plugged the line. and after a few hundred miles, I was able to tighten the gas cap with no issues. AFAIK, dhise hasn't had any problems with it since. I know he got 32mpg on the way back to detroit, so I don't think it was leaking anywhere

[Gloyale]

Didn't your friend's car have the fuel pump in the engine bay?

 

GD

 

OE pump was up in the engine bay.

 

We mounted the FI fuel filter there.

 

And mounted the new FI pump back by the tank. (there was a filter back there, pump fits right in the filter bracket.

 

 

Any hints as to ho the vent and the return lines are tied toghether would be great.

[GeneralDisorder]

Ok - so taking a look at my '80 FSM.... the vent and return lines are never tied together - only in as much as both of them eminate from the tank.

 

But there are two other devices in the vent line - there is a fuel seperator behind the passenger side wall in the rear cargo area - it's like a mini fuel tank that drains back to the tank from the bottom and releases vapor from the top. Then under the car there is a 2-way valve that maintains constant pressure in the tank - allows vapor out, and fresh air in, but is closed unless there is a pressure differential.

 

I would surmise that the fuel seperator or it's tank return line are clogged - it's likely full of fuel and the pressure being created by the FI pump is enough to force said fuel through the vent line to the engine bay.

 

One thing that concerns me is that the system does not show a filter back by the tank - only the 2-way valve in the vent line. Are you sure it was a filter you removed and replaced with the pump and not said 2-way valve? My FSM is an '80 and your's is an '81 so maybe there was a filter that my diagram doesn't show - but I figured I should mention it.

 

GD

[SoobieDoo]

Yeah, I've found the california cars to have a completely different fuel system. Mine's a '86, but they may still have some things in common. One filter only, at the tank. In my case, I believe the fuel return line to be causing tank pressure. It always had when the original hitachi was on, then it was disconnected with a weber on. No pressure, no leakage. Now with the EJ, it will not only pressurize the tank, but will leak. I think it's the higher pressure of the pump, and they're connected through the engine. Is flow coming from the firewall, or the engine side?

Edited March 22, 2010 by SoobieDoo
question

[Gloyale]

Yeah, I've found the california cars to have a completely different fuel system. Mine's a '86, but they may still have some things in common. One filter only, at the tank. In my case, I believe the fuel return line to be causing tank pressure. It always had when the original hitachi was on, then it was disconnected with a weber on. No pressure, no leakage. Now with the EJ, it will not only pressurize the tank, but will leak. I think it's the higher pressure of the pump, and they're connected through the engine. Is flow coming from the firewall, or the engine side?

 

Fuel from small tube coming through the firewall.

[Gloyale]

 

One thing that concerns me is that the system does not show a filter back by the tank - only the 2-way valve in the vent line. Are you sure it was a filter you removed and replaced with the pump and not said 2-way valve? My FSM is an '80 and your's is an '81 so maybe there was a filter that my diagram doesn't show - but I figured I should mention it.

 

GD

 

The filter was a large metal can type, probably from jeep or something, that someone had shoved in there, presumably in place of the original. It was the only filter in the system.