When did the return lines start appearing?? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**JJorgensen52** · 03-23-2013, 05:51 PM

I'm having a problem with my new '72 1ton GMC. It's a 350/4bbl and so far as I can tell it has only a supply, no return. The build date is 11/71 if that makes a difference.

Anyway, the problem is that I get a fuel starving problem under any kind of load ... new fuel pump and hard/rubber lines on the frame, the line in the cab is original. I'm leaning towards the filter inside the tank?? Could carb filter cause this issue? The fuel siphons from the tank easily and the pump is pushing plenty of fuel sitting still.

Shyguy · 03-23-2013, 08:06 PM

I don't think the lines that went to the carbon filter were called return lines, but many people call them that.

In California I think the vapor vent line that went from the gas tank to the carbon filter started in 1971 with C-10s. My '72 GMC 3/4 ton did not have one.

The actual return lines from the fuel pump started sometime after 1972, the '74 454 we put in my '67 had the return line on the fuel pump.

Hopefully someone else will chime in with more info.

Some of the things that can cause fuel starving are plugged fuel filter in Q-jets inlets, collapsing rubber hoses, bad fuel pump, cracked rubber hoses, collapsed sock on sending unit in tank and unvented gas caps.

**JJorgensen52** · 03-23-2013, 09:17 PM

Quote:

Originally Posted by Shyguy

Some of the things that can cause fuel starving are plugged fuel filter in Q-jets inlets, collapsing rubber hoses, bad fuel pump, cracked rubber hoses, collapsed sock on sending unit in tank and unvented gas caps.

There is most definitely no charcoal can on this truck, never was, so I think that's out.

I'm going to check the gas cap here in a minute, I'll just swap it with the one from my '69. Also going to check the filter in the Q-jet, didn't think of that yesterday.

TripleNickel · 03-23-2013, 11:13 PM

Quote:

Originally Posted by Shyguy

In California I think the vapor vent line that went from the gas tank to the carbon filter started in 1971 with C-10s.

My Fremont built, Central Valley delivered '70 C-10 (with October '69 build date) has a return to the tank... and it was a nearly un-optioned 250 with 3 on the tree.

Gumby · 03-24-2013, 12:54 AM

first came about from the heat under the hood of big GMs with AC would cook the fuel causing vapor lock, and was an either or type thing.

Davemotohead · 03-24-2013, 01:05 AM

My CA 71 only had a charcoal canister with no return line,,check the carb stone filter and all the inlet lines,,sometimes you can have a leak that does not leak gas but sucks air when its running.

03-23-2013, 05:51 PM	#1
JJorgensen52 Simple? What's simple? Join Date: Apr 2007 Location: Southeast CT Posts: 1,472	When did the return lines start appearing?? I'm having a problem with my new '72 1ton GMC. It's a 350/4bbl and so far as I can tell it has only a supply, no return. The build date is 11/71 if that makes a difference. Anyway, the problem is that I get a fuel starving problem under any kind of load ... new fuel pump and hard/rubber lines on the frame, the line in the cab is original. I'm leaning towards the filter inside the tank?? Could carb filter cause this issue? The fuel siphons from the tank easily and the pump is pushing plenty of fuel sitting still. __________________ CURRENT '50 GMC 100 shortbed Gen IV 4.8 LS - 4L65E (Secret truck, Shhh!!!) Build '63 Buick Wildcat Coupe 401ci Nailhead (Very much in pieces) Photos '66 Impala SS convertible 327-QJet-glide (4 speed swap one of these days...) Photos '69 CST/10 4x4 SWB Stepper 350 2bbl - NV4500/NP241C (Broken Truck!) '72 Sierra Grande 2WD LWB fleetside 350-TH350 Refresh '99 K2500 Silverado RCLB 5.7 Vortec - NV4500/NP241C (Daily) '99 K2500 Suburban 7.4 Vortec - NV4500/NP246 (still working out the bugs) SOLD '71 Custom/10 2WD LWB fleetside - '72 GMC K/3500 Dually (Sold to redryder)

03-23-2013, 08:06 PM	#2
Shyguy Junior Member Join Date: Dec 2006 Location: Southeast Missouri Posts: 2,436	Re: When did the return lines start appearing?? I don't think the lines that went to the carbon filter were called return lines, but many people call them that. In California I think the vapor vent line that went from the gas tank to the carbon filter started in 1971 with C-10s. My '72 GMC 3/4 ton did not have one. The actual return lines from the fuel pump started sometime after 1972, the '74 454 we put in my '67 had the return line on the fuel pump. Hopefully someone else will chime in with more info. Some of the things that can cause fuel starving are plugged fuel filter in Q-jets inlets, collapsing rubber hoses, bad fuel pump, cracked rubber hoses, collapsed sock on sending unit in tank and unvented gas caps. __________________ '67 Chevy C-20 short stepper - build complete, 454/SM-465. '75 C-30 Single Cab DRW-350 small block/NP-435. '77 GMC-6500 Dump Truck, 427 Tall Deck. '92 GMC K-3500 Duallie, 454/4L80E.

03-24-2013, 12:54 AM	#5
Gumby Registered User Join Date: Dec 2008 Location: NW-Ohio Posts: 2,525	Re: When did the return lines start appearing?? first came about from the heat under the hood of big GMs with AC would cook the fuel causing vapor lock, and was an either or type thing.

03-24-2013, 01:05 AM	#6
Davemotohead Registered User Join Date: Sep 2011 Location: rosamond ca Posts: 130	Re: When did the return lines start appearing?? My CA 71 only had a charcoal canister with no return line,,check the carb stone filter and all the inlet lines,,sometimes you can have a leak that does not leak gas but sucks air when its running. __________________ edited by staff



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