does my fuel tank have a surge tank?

vladrulli · Post by **vladrulli** » Wed Nov 16, 2005 4:57 am

ok, still trying to solve fuel problems on my ej20t converter GL Coupe...

I originally thought that my tank did not have a built in surgtank... now I'm not sure... I looked under some other subarus and there were no return lines to the tank (carby engine)... now, my car had a carby engine too but there is a return line running back to the fuel tank... does that mean anything? might I be so lucky that my car has a tank with a built in surge tank?

vladrulli · Post by **vladrulli** » Wed Nov 16, 2005 8:07 pm

Suba · Post by **Suba** » Wed Nov 16, 2005 8:11 pm

What set-up do you have at the momment with you fuel system.

Mike.

vladrulli · Post by **vladrulli** » Wed Nov 16, 2005 9:53 pm

well, I was trying to use a surge tank but I've always had problems with it... it leaks and creates too much back-pressure on the return line...
would really like to simply run the lines directly to the fuel tank and use only on HP pump instead of one LP and one HP...

fredsub · Post by **fredsub** » Wed Nov 16, 2005 10:16 pm

. I looked under some other subarus and there were no return lines to the tank (carby engine)...

That would have to be some old subie.....The L series carby have 2 return
lines, one for fuel (excess from carby) and the larger return line for vapour,connecting the charcoal canistor and the evaporative mechanism at the fuel filler.
You have to remember with the more modern engine you got there, you really need this full deal, and circulating fuel only warms it more and tends to create more vapour pressure in the system.

.......car has a tank with a built in surge tank?

not real sure what your thinking of there

perhaps I should mention that (I guess) any EFI based car, have fuel tanks with baffles in them, so alleviating the need for a separate surge tank.
For a carburettor such things are unnecessary because 1) the fuel pump is low pressure, 2)the carby itself has a reserve of fuel in its bowl

vladrulli · Post by **vladrulli** » Fri Nov 18, 2005 8:04 am

ok, what would be the best way to do this? anyone with a rought diagram?

I was thinking of taking out the fuel tank to widen the return opening so I could run a bigger return line... then what? put a surge tank between the hp and lp pumps and let the lp pump constantly try to fill it up? should I run a t-piece on the return line and let a part of the fuel go back to the surge tank?

wagonist · Post by **wagonist** » Sat Nov 19, 2005 12:22 pm

AFAIK, all L series MPFI EFI tanks have a surge tank built in & all L series tanks have a return line. There should be 2 lines coming out of the front of the tank (one bolts to the rear suspension)
I'm also sure that they have bigger fuel line fittings to the carb version. ie EFI retun line is same size as carb feed line, & EFI feed is bigger again.

Where are you running the return line to? The surge tank or the fuel tank?
The return line should be to the surge tank & the overflow from the surge tank back to the fuel tank. If you're not doing it this way, then your lift pump (carb) won't keep up with the demand of the EFI system.

If its leaking I would suggest that you're not using EFI grade fuel lines & clamps (not worn type hose clamps)