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#1 |
Registered User
Join Date: May 2010
Location: Seattle
Posts: 12
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Help!! Can't figure this out!!!
I have a 70 gmc with factory 396/402 big block. The truck runs fine at start up and when it gets up to running temp it starts to run out of gas! I put a new fuel pump on(mechanical) and also blew the line out back up threw the tank so I know the line is clear also rebuilt the carb. I have clear fuel filter on it so i can see what the fuel is doing. When I shut the truck off and the motor cools the fuel comes back. The truck does have two saddle tanks but I don't use them. The truck has headers to. I'm lost any advice?
Posted via Mobile Device Last edited by Seatown-gmc; 10-06-2012 at 07:15 PM. |
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#2 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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Just a thought. Next time when you crank it let it run then shut it off when it starts doing it. Then crack the gas cap and see if it's pulling vacum on it. U should here it sucking air into the tank. If so get a vented gas cap are check the vent line for being clogged.
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#3 |
Registered User
Join Date: May 2010
Location: Seattle
Posts: 12
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Re: Help!! Can't figure this out!!!
Cool ill try that! Thanks for the reply!
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#4 |
Member
Join Date: Jan 2011
Location: Stuart, Florida
Posts: 459
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Re: Help!! Can't figure this out!!!
Maybe a piece of trash in your fuel tank? Should be a screen but it could have come off.
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1970 CST LB Fleetside, 402 BB, PS, PB,AC 1968 Firebird 400 conv. 1965 Chris Craft 17' wood ski boat (SN #0001) |
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#5 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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Let us know what u find out.
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__________________
1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#6 |
Registered User
Join Date: Mar 2010
Location: Cheyenne Wy
Posts: 208
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Re: Help!! Can't figure this out!!!
Not sure this applies but,
I had the same symptoms in my 72 olds 442 after replacing old pump, turns out it was vapor locking. Next time it starts to act up touch the fuel pump to see if it is hotter than normal. I had a clear plastic fuel filter in the line near the carb when the engine got to operating temp there was no more gas. I tried to get a spacer to get the pump off the block, ended up going with a electric.
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________________________ 72 Olds Cutlass w/442 option 69 C-10 Short Bed Fleet 1960 Biscayne Wagon/El Camino 1995 YJ 4.0 SOA SYE on 35s 01 Excursion Limited 7.3 PSD 06 Suzuki DRZ 400S |
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#7 |
Registered User
Join Date: May 2010
Location: Seattle
Posts: 12
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Re: Help!! Can't figure this out!!!
I did pour water down the line from the filter to the pump when it was running and the fuel seemed to come back. The pump could be getting hot. Is that normal with a factory set up?
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#8 |
Registered User
![]() Join Date: Jul 2010
Location: mogadore ohio
Posts: 867
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Re: Help!! Can't figure this out!!!
is the fuel line from the tank ran inside the frame rail? my buddy put a 402 in a 73-87 body style truck that originally came with a small block and the fuel line would vapor lock when the engine warmed up. the 73-87 big block trucks have the fuel line ran on the outside of the frame rail. the "C" of the frame holds the heat.
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1969 chevy c10 lwb stepside 250 6 3 ott 1971 chevy c10 lwb 250 6 with power steering 3 ott 1972 chevy k20 4x4 350/TH350 automatic 1978 chevy Malibu 4dr 305 2bbl (all original) 1979 chevy k10 Scottsdale 350/th350 full-time 4wd(daily driver) |
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#9 |
Registered User
![]() Join Date: Jan 2011
Location: Chattanooga TN
Posts: 6,208
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Re: Help!! Can't figure this out!!!
An old hot rodder's trick is to clip two wooden clothes pins on various places of the fuel line from the pump to the carb. It will cause the heat to dissipate off the line.. if this makes it better, I'm thinking vapor lock too.
Do you have an Edelbrock carb?
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Chad 1967 C10 SWB - Project Savannah - 6.0/4L80 *Currently underway* 1968 C10 SWB - TOTY 2018, 50th Anniversary Tribute Project * Sold * Pride and Joy 1986 Silverado Short Fleet - Scarlet *Sold* 1985 Silverado Short Fleet *Sold* 2022 Jeep Gladiator Mojave 2001 Jeep Cherokee XJ 4x4 - Lifted, Built 1992 Jeep Cherokee XJ 4x4 - Lifted 2013 Honda Accord EX-L v6 Coupe 6spd (wife's ride) |
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#10 |
Registered User
![]() Join Date: Sep 2009
Location: Prescott Valley AZ
Posts: 345
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Re: Help!! Can't figure this out!!!
LOL I had a flat plastic bread tie in my tank once. The sock was long gone and after about a 2-5 miles of driving it would suck right to end of the pick up. Just thought I'd share. On another note I have heard the Edelbrock carbs are bad about cooking the fuel with out a thick carb gasket.
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#11 |
Registered User
![]() Join Date: May 2012
Location: Anton, Texas
Posts: 2,364
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Re: Help!! Can't figure this out!!!
there could be something inside the tank that sucks up to the fuel line, i have seen this before...i also have fixed several by putting a three line fuel pump on and running the small return line back to the top of the tank and installing a fitting on the tank so the fuel keeps moving and has time to cool off, this works very good with the old carter afb...that is now the edelbrock , they can't stand any dirt,and flood real easy when pressure goes up...i have done this to the q-jet with much success ....hope this helps.
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#12 |
Registered User
Join Date: Aug 2012
Location: Indiana
Posts: 470
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Re: Help!! Can't figure this out!!!
another fix would be if the pump is the problem getting to much heat, wrap your headers with the high temp header wrap found at most of your car parts stores, i did this to my 70 and i love it, engine runs so much cooler, and i gained HP and the engine bay is much quieter, i used the bran DEI good stuff
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70 C10 working on a LSx swap ![]() 4.8L MS3 edelbrock pro flo intake, pacesetter long tubes, 4l60e 2500 stall hoping the tranny holds up lol |
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