Truck won't start - fuel or acc. pump? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**JQ-72** · 10-15-2017, 04:46 AM

Stock 350 with Edelbrock carb. When the truck sits for a day or longer, it will not start back up. Pour a little gas in the carb and she starts like a champ and runs/restarts the rest of the day. Accelerator pump bad or fuel pump leaking down? How do I tell? Thanks for any help.
JQ

cadillac_al · 10-15-2017, 08:02 AM

A good fuel pump should be able to pull fuel from the gas tank in 15 seconds or less. I had a pin hole leak in a rubber line at the tank once that was hard to find. That made for some hard starts. I found it when I tried to pull fuel with a Mityvac and heard it hissing.

RustyBucket · 10-16-2017, 09:17 AM

After it sat for a day or two i'd check the accelerator pump delivery. I wonder if the float bowl is leaking. When you prime the carb. it runs enough to refill the bowl, then you're good to go for the day. Don't know 'bout Edelbrocks but Quadrajets used to be bad about draining into the intake. Caused the same problem you're having. Had to turn on the starter a long time to refill the float bowl. I wouldn't think fuel would siphon or drain back down through the fuel pump. I think if the accelerator pump was bad it wouldn't run right after you get it started by priming the carburetor.

**Ironangel** · 10-17-2017, 10:22 AM

Next time you shut down the motor, pull the breather and see if you can see fuel dripping from the primary and/or the secondary booster venturi's. If so, it's probably time for a rebuild and if you havent done so already, get a 1/4" thick base gasket and/or a phenolic plastic spacer under the carb to insulate the carbs fuel bowl. Just the heating of the fuel in the bowl will expand it enough to push fuel past the weak or leaking check valves. The siphoning effect will all but drain the bowls while the fuel drains back down the fuel line as well. Keeping the tank full should help keep fuel from siphoning back down past the pump as well.

68gmsee · 10-17-2017, 02:47 PM

Something is causing the loss of fuel from the carb. I'd take the top of after it sits for a day or two to see if there's fuel in the bowl.

If there is, then the accelerator pump may not be pushing fuel into the engine as mentioned above. When you give it a shot of fuel to start it, the engine vacuum would then suck fuel into the engine to keep it running.

I'm not very familiar with Edelbrocks but if it doesn't have well plugs like q-jets then about the only other thing I can think of is the needle valve not sealing allowing fuel to drain back out of the bowl. Also as mentioned above a good fuel pump should replenish the fuel in the bowl very quickly. I let my 68 GMC sometimes sit for a week and it starts back up in about 10 seconds of cranking with choke on.

10-15-2017, 04:46 AM	#1
JQ-72 Senior Member Join Date: Feb 2001 Location: Killen, Alabama USA Posts: 3,539	Truck won't start - fuel or acc. pump? Stock 350 with Edelbrock carb. When the truck sits for a day or longer, it will not start back up. Pour a little gas in the carb and she starts like a champ and runs/restarts the rest of the day. Accelerator pump bad or fuel pump leaking down? How do I tell? Thanks for any help. JQ __________________ 72 Cheyenne Super swb. Factory 402/400,tach,posi,AM/FM, A/C. Adding cruise, 8-track 72 Cheyenne Super swb. 350/350 A/C, bucket seats 72 Cheyenne swb. Factory 402/400, tilt, posi, A/C 72 Cheyenne Super K-10. 350/4 spd., posi. 72 Suburban 350/350 tilt, tach, AM/FM, A/C, luggage rack 72 GMC Sierra lwb. 350/350, A/C. medium green/olive interior

10-15-2017, 08:02 AM	#2
cadillac_al Registered User Join Date: Oct 2013 Location: Maine Posts: 2,340	Re: Truck won't start - fuel or acc. pump? A good fuel pump should be able to pull fuel from the gas tank in 15 seconds or less. I had a pin hole leak in a rubber line at the tank once that was hard to find. That made for some hard starts. I found it when I tried to pull fuel with a Mityvac and heard it hissing. __________________ 76 Chevy K20 76 GMC K15 77 Chevy C10 77 Chevy K10

10-16-2017, 09:17 AM	#3
RustyBucket Registered User Join Date: Jul 2009 Location: Space Coast, Fl. Posts: 1,050	Re: Truck won't start - fuel or acc. pump? After it sat for a day or two i'd check the accelerator pump delivery. I wonder if the float bowl is leaking. When you prime the carb. it runs enough to refill the bowl, then you're good to go for the day. Don't know 'bout Edelbrocks but Quadrajets used to be bad about draining into the intake. Caused the same problem you're having. Had to turn on the starter a long time to refill the float bowl. I wouldn't think fuel would siphon or drain back down through the fuel pump. I think if the accelerator pump was bad it wouldn't run right after you get it started by priming the carburetor. __________________ Dad always said, "Son, WISH IN ONE HAND, and ......." -------------------------------------- -------------------------------------- Current toy trucks: '71 GMC 1500 SUPER CUSTOM short/step, orig. dk. blue, 350/700r, ps,pb, A/C '72 Blazer 2wd, ochre & white, 454, tremecTKO 500 5spd. ps, pb, A/C, tilt Last 10yrs of hobby vehicles, had a FEW more in the 50yrs. before these: '66 Plymouth Belvedere City of Miami cop car clone. '70 Nova 406"sb, 13.5-1, solid roller, Brodix, p.glide/t.brake, back halved, 9" Ford, spool 4.88, cage,ladder bar/coilover, 10.5 tire....... SOLD!! '67 C10 short/step side mount spare -- SOLD!! '72 Jimmy 2wd, 350/350, ps, pb, fun driver, lots of bondo & a shiny red paint job..... SOLD!! '69 Nova 350, 4spd, A/C, ps, p.b, ...SOLD!! Last edited by RustyBucket; 10-16-2017 at 09:39 AM. Reason: typoo

10-17-2017, 10:22 AM	#4
Ironangel Senior Member Join Date: Feb 2010 Location: Falls City, Nebraska "100 Miles From Nowhere" Posts: 2,219	Re: Truck won't start - fuel or acc. pump? Next time you shut down the motor, pull the breather and see if you can see fuel dripping from the primary and/or the secondary booster venturi's. If so, it's probably time for a rebuild and if you havent done so already, get a 1/4" thick base gasket and/or a phenolic plastic spacer under the carb to insulate the carbs fuel bowl. Just the heating of the fuel in the bowl will expand it enough to push fuel past the weak or leaking check valves. The siphoning effect will all but drain the bowls while the fuel drains back down the fuel line as well. Keeping the tank full should help keep fuel from siphoning back down past the pump as well. __________________ Michael of the clan Hill, "Two Seventy Two's" 71 1-ton Dually 350 4-Speed 71 C/50 Grain Truck, 350 Split-Axle 4-Speed 02 3/4 ton Express 14 Indian Chief Vintage 1952 Ford 8N, "Only Ford Allowed On The Property" "Be American, Buy American" Last edited by Ironangel; 10-17-2017 at 10:33 AM.

10-17-2017, 02:47 PM	#5
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Truck won't start - fuel or acc. pump? Something is causing the loss of fuel from the carb. I'd take the top of after it sits for a day or two to see if there's fuel in the bowl. If there is, then the accelerator pump may not be pushing fuel into the engine as mentioned above. When you give it a shot of fuel to start it, the engine vacuum would then suck fuel into the engine to keep it running. I'm not very familiar with Edelbrocks but if it doesn't have well plugs like q-jets then about the only other thing I can think of is the needle valve not sealing allowing fuel to drain back out of the bowl. Also as mentioned above a good fuel pump should replenish the fuel in the bowl very quickly. I let my 68 GMC sometimes sit for a week and it starts back up in about 10 seconds of cranking with choke on. __________________ 68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive...



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