fuel pump - The 1947 - Present Chevrolet & GMC Truck Message Board Network

fjmiii327 · 12-06-2007, 12:40 AM

My '72 has a fuel pump failure and I have a new pump that dont have provision for return system. Can I run the new pump and just cap off the fuel return line ? Is this a bad idea ? What is the purpose of a return system anyway ?

1972 Chevy Cheyenne K20
350/465/205

dave2953 · 12-06-2007, 12:59 AM

I've always heard that you can cap off the return with no problems. I think the return just sends back the excess, but I'm not certain.

JimKshortstep4x4 · 12-06-2007, 05:22 AM

Welcome to Chevy Trucks from West Michigan!

The 72 system has a pressurized gas cap and the return on the fuel pump is part of the emissions control to keep gas vapors from escaping into the atmosphere.

Since you live in California, my suggestion would be to put the correct fuel pump back on. While the other pump can be made to work you may be better off with the return style pump.

Jim

Tx Firefighter · 12-06-2007, 06:54 AM

Jim is right. Besides, the proper fuel pump is still available at the parts store for the same price as the wrong one.

Welcome aboard too.

fjmiii327 · 12-06-2007, 12:37 PM

Alright, I guess I better use the correct pump then. Thanks guys.

wzuke · 12-10-2007, 01:45 AM

Does the '71 use the same system or just the '72?

JimKshortstep4x4 · 12-10-2007, 05:46 AM

All of the 71 trucks that I have seen use a different pump as the tank has a line that goes back to the charcoal filter. There could be exceptions, though.

Jim

Wrenchbender Ret · 12-10-2007, 09:43 AM

I always thought it came on A/C models & was for pressure regulating.

piecesparts · 12-10-2007, 11:07 AM

The return line is NOTHING more than a small orificed outlet from the same pump side as the feed to the carb. It can be capped off and not affect anything.

On the opposite side of the coin:

On my 84 GMC, I put in an Edelbrock racing pump and did not hook up the return and I had a created a fuel vaporlock problem by not putting the return back on. so I mounted their different ooutlet block on the bottom of the pump and put in an orificed outlet to do the return line--it stopped the fuel vapor lock problem.

wzuke · 12-10-2007, 10:01 PM

I'm still not sure I understand which pump the '71 is supposed to have. Is it the pump with two outlets, one for the carb and the other for the return or just one outlet for the carb?

piecesparts · 12-11-2007, 09:48 AM

If you have a pump that has two (2) outlets and one of them is a small line with a very small hole in it, then it is most likely for the later model SMOG related trucks. My old 72 had a fuel pump with an inlet and one (1) outlet connection and that was all. IF you do not have an extra line (return) on the frame, by the fuel pump then you do not need a return design fuel pump. If you happen to have a fuel pump with two (2) outlets, then plug the really small one off with a capped off hose and go forward, it will work just fine.

12-06-2007, 12:40 AM	#1
fjmiii327 Registered User Join Date: Sep 2007 Location: Bakersfield, CA Posts: 7	fuel pump My '72 has a fuel pump failure and I have a new pump that dont have provision for return system. Can I run the new pump and just cap off the fuel return line ? Is this a bad idea ? What is the purpose of a return system anyway ? 1972 Chevy Cheyenne K20 350/465/205

12-06-2007, 12:59 AM	#2
dave2953 Dave's not here, man Join Date: Jun 2004 Location: Winder, Georgia Posts: 2,000	Re: fuel pump I've always heard that you can cap off the return with no problems. I think the return just sends back the excess, but I'm not certain. __________________ - 2014 VW Jetta - 2015 VW Jetta - 1966 Ford F-250

12-06-2007, 05:22 AM	#3
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: fuel pump Welcome to Chevy Trucks from West Michigan! The 72 system has a pressurized gas cap and the return on the fuel pump is part of the emissions control to keep gas vapors from escaping into the atmosphere. Since you live in California, my suggestion would be to put the correct fuel pump back on. While the other pump can be made to work you may be better off with the return style pump. Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

12-06-2007, 06:54 AM	#4
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: fuel pump Jim is right. Besides, the proper fuel pump is still available at the parts store for the same price as the wrong one. Welcome aboard too. __________________ I'm on the Instagram- @Gearhead_Kevin

12-06-2007, 12:37 PM	#5
fjmiii327 Registered User Join Date: Sep 2007 Location: Bakersfield, CA Posts: 7	Re: fuel pump Alright, I guess I better use the correct pump then. Thanks guys.

12-10-2007, 01:45 AM	#6
wzuke Registered User Join Date: Nov 2007 Location: Marion, IL Posts: 112	Re: fuel pump Does the '71 use the same system or just the '72?

12-10-2007, 05:46 AM	#7
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: fuel pump All of the 71 trucks that I have seen use a different pump as the tank has a line that goes back to the charcoal filter. There could be exceptions, though. Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

12-10-2007, 09:43 AM	#8
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,229	Re: fuel pump I always thought it came on A/C models & was for pressure regulating.

12-10-2007, 11:07 AM	#9
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: fuel pump The return line is NOTHING more than a small orificed outlet from the same pump side as the feed to the carb. It can be capped off and not affect anything. On the opposite side of the coin: On my 84 GMC, I put in an Edelbrock racing pump and did not hook up the return and I had a created a fuel vaporlock problem by not putting the return back on. so I mounted their different ooutlet block on the bottom of the pump and put in an orificed outlet to do the return line--it stopped the fuel vapor lock problem.

12-10-2007, 10:01 PM	#10
wzuke Registered User Join Date: Nov 2007 Location: Marion, IL Posts: 112	Re: fuel pump I'm still not sure I understand which pump the '71 is supposed to have. Is it the pump with two outlets, one for the carb and the other for the return or just one outlet for the carb?

12-11-2007, 09:48 AM	#11
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: fuel pump If you have a pump that has two (2) outlets and one of them is a small line with a very small hole in it, then it is most likely for the later model SMOG related trucks. My old 72 had a fuel pump with an inlet and one (1) outlet connection and that was all. IF you do not have an extra line (return) on the frame, by the fuel pump then you do not need a return design fuel pump. If you happen to have a fuel pump with two (2) outlets, then plug the really small one off with a capped off hose and go forward, it will work just fine.



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