Home » Public Forums » GMCnet » [GMCnet] So what micron in line fuel filter would be needed for EFI. Since my carb filter got plugged after an in line filter?
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| Re: [GMCnet] So what micron in line fuel filter would be needed for EFI. Since my carb filter got plugged after an in line filter? [message #322649 is a reply to message #322644] |
Fri, 25 August 2017 18:06   |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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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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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] So what micron in line fuel filter would be needed for EFI. Since my carb filter got plugged after an in line filter? [message #322660 is a reply to message #322649] |
Fri, 25 August 2017 19:10 |
kstockwell
Messages: 367
Registered: May 2016
Location: Putney VT
Karma: 4
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Senior Member |
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Thanks Ken!
Completely makes sense. I don't want to run any fuel lines anywhere but I see why it would be good if you had those lines. The one I have doesn't have a return line, I was just curious about why the other would be "recommended".
I realize we're not all stock stuff.
The fuel pump was put in by the PO just before selling it to me. I'll be putting in the WIX fuel filter inline before it at some point.
-kelly
Ken Henderson wrote on Fri, 25 August 2017 19:06Kelly,
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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GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
1978 Kingsley
Putney VT
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