Kelly,

The mechanical fuel pump with the return line was original equipment on air
conditioned Toronados; it was never OEM on the motorhome. The return line
has a small orifice to allow a small amount of liquid or a large amount of
vapor to return to the fuel tank, through a dedicated return line (which
the GMC doesn't have as original equipment). That tends to alleviate mild
vapor lock by allowing the un-useable vapor to return to the tank.

IMHO, an electric pump (preferably two, one for each tank, replacing the
selector valve) back near the tanks, is a far better solution for vapor
lock as well as for redundancy and simplicity.

You DO NOT want that "feedback" pump unless you add the return line. Many
people have, for whatever reason, installed that pump without the return
line and then plugged the return fitting -- usually with a short piece of
hose, a 3/8" bolt and a couple of hose clamps -- An almost certain formula
for leakage, sooner or later.

NAPA's part number for the two pumps is only one digit apart -- I don't
remember either.

Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, etc., etc., etc.
www.gmcwipersetc.com

On Fri, Aug 25, 2017 at 5:42 PM, kelly stockwell wrote:

> I am looking to carry an extra fuel pump. I see the one suggested does
> not have a return line, and there's another that does.
>
> In the parts lookup online (not right by any means) it says the one with
> the return line is right for my "Olds Toronado" engine. Of course I
> wouldn't
> buy that one because of the online thing; but it did make me look up what
> the heck the return line does, and from what I can tell its supposed to help
> minimize gas boiling away (vapor lock?). Is that an issue I hear people
> have with these engines? Can someone explain how the return line works, how
> it would minimize gas boiling, and then tell me why we get the pump
> without a return line?
>
> I'm trying to learn/understand how stuff works; so pretend I know nothing
> and you're close
>
> thanks, i hope I'm not hijacking this thread.
>
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