I have converted my 1980 Mercury Zephyr to EFI. The Mustang style fuel tank will not fit, so I used the "tried and true" Competition Engineering weld-on tank sump. Everything is WONDERFUL until I get below 3/4 tank and it just gets worse as the fuel level drops.

What is obviously happening is that as the fuel sloshes around, the pickup oriface gets uncovered and the pumps suck vapor, not fuel.

I am trying to avoid installing a fuel cell, I really want to use the stock style tank.

Does anyone know of a commercially available vapor bypass or how to construct something that will return the vapor to the tank and only send liquid fuel to my engine ?

I've considered filling my stock tank with fuel cell foam, but that would interfere with the gauge sending unit and this is a daily driver, not a race car, so I really like having a functioning fuel gauge.

I have a few ideas that I am mulling over, but I thought I'd throw this out there to see if anyone else has dealt with this. And, YES, I did search the forums before posting this question.

Thanks !
-D Payne

 

did you cut the entire area out to weld the sump on or did you just hole saw the area where the sump gets welded on?

 

No, I didn't cut the entire patch out.

I anticipated this problem ( although I didn't think it would be THIS bad ).

Instead of holes, I cut flaps into the area where the sump is welded and bent them downward so that fuel will flow in and ( I thought ) be less likely to flow out than a big hole or array of holes...

SOMEONE must have some way of bypassing vapor back to the tank....

 

I know this doesn't really answer your question, but it's the easiest way I've found to convert an early Fox to EFI.

I have a 78 Fairmont, so I kinda know what you're talking about. What I did was get a tank and fuel pump hanger/sending unit for a 84-86 LTD II wagon with a TBI 3.8. I then replaced the low pressure pump with a Walbro GSS 340 that is spec'ed for a GM application, so it has an offset inlet. It made my EFI conversion pretty much bolt-in. I'm not on my personal computer, otherwise I'd have a list of all the part numbers and links to where you can find them. Hope this helps.