Start up issue - The 1947 - Present Chevrolet & GMC Truck Message Board Network

KellerMAC · 10-30-2017, 09:17 AM

I have a recently rebuilt 72 C10 and it sits during the week and on weekend when I go to start it, I have to pump the gas pedal and turn it over for about a minute before it finally starts up - I drive it through out the weekend and it starts on first turn. Then when I let it sit for the next week, it's hard to start and we go thru the same process again. I have a manual fuel pump on it. Is there anything I can do so it is ready to start after a week long layoff?

Thanks,

geezer#99 · 10-30-2017, 09:22 AM

What carb?

KellerMAC · 10-30-2017, 02:31 PM

Rochester 4 barrel - factory carb - 350 engine - recently rebuilt carb and engine

**truckster** · 10-30-2017, 02:50 PM

Did you replace the filter in the carb inlet, and does it have the flowback preventer valve in it?

Also, did you set the float level according to the instructions in the rebuild kit?

beadblaster · 10-30-2017, 02:53 PM

Leaking fuel plugs on bottom of carb. Common problem.

MARKDTN · 10-31-2017, 11:20 AM

Quote:

Originally Posted by beadblaster

Leaking fuel plugs on bottom of carb. Common problem.

agree

**Stocker** · 10-31-2017, 01:03 PM

Quote:

Originally Posted by truckster

Did you replace the filter in the carb inlet, and does it have the flowback preventer valve in it?

Not to hijack.... My Q-jet acts similar to the OP's, the longer it sits, the more it needs to be cranked over before it will start. Carb has been rebuilt, leaking fuel plugs sealed, new mechanical fuel pump, newish filter at the carb's fuel inlet.

Maybe there's an issue with the flowback preventer valve and it would help if I knew what I was looking for. Any further info would be appreciated -- pic, diagram, etc. I have never heard of it before now.

Toms67 · 10-31-2017, 01:21 PM

Is the Axcelerator pump working? When you pump it. Did you look in the carburetor and see if it was getting gas? With it not running.Sometimes they dry out. And when you get them wet again. it might work for a while.

**truckster** · 10-31-2017, 01:26 PM

Quote:

Originally Posted by Stocker

Not to hijack.... My Q-jet acts similar to the OP's, the longer it sits, the more it needs to be cranked over before it will start. Carb has been rebuilt, leaking fuel plugs sealed, new mechanical fuel pump, newish filter at the carb's fuel inlet.

Maybe there's an issue with the flowback preventer valve and it would help if I knew what I was looking for. Any further info would be appreciated -- pic, diagram, etc. I have never heard of it before now.

It's a little black rubber piece on the end of the filter. Most paper filters have them.

LSSierra · 10-31-2017, 02:45 PM

Wow my 71 with a Q-Jet also does the same thing. Where is the best place to start troubleshooting?

**Stocker** · 10-31-2017, 03:16 PM

Quote:

Originally Posted by truckster

It's a little black rubber piece on the end of the filter. Most paper filters have them.

Thanks! I'll make sure it's there... if not, I'll get a new filter and make sure it has that flap. I don't recall seeing it before, though....

*randy500* · 10-30-2017, 02:53 PM

Fuel pump is probably leaking fuel back to tank and has to refill line and carb, how old is the fuel pump.
You can check this by removing the line and seeing how much fuel is in it.
There is a check valve in the pump that when operating correct prevents drain back.

geezer#99 · 10-30-2017, 03:54 PM

Is your divorced choke new too?
Did you clean out the crossover in the intake during the rebuild?

demian5 · 10-31-2017, 03:17 PM

I believe this is just part of owning a carburated vehicle. We are all spoiled with fuel injection and all these bells and whistles. Yeah this is an issue that can be fixed, but its so common of carb vehicles that its almost like a theft deterrent!

garyd1961 · 10-31-2017, 08:37 PM

You could install an electric fuel pump. It would pump fuel up to the carb before the motor turns over.

Zogbert · 11-01-2017, 07:48 AM

Had the same issue. Replaced the fuel pump, and that ended the problem.

bandit0067 · 11-01-2017, 12:11 PM

I would bet the fuel plugs are leaking the bowls dry when sitting the short time. Then the fuel pump takes a bit to fill the bowls back up. If you want a quicker start, the bowl air vent tube, yes, that 1/4 inch "tube" that is slanted back towards the breathed stud, on top of the carb, you can squirt a few shots of fuel directly into the bowls. And then maybe a small squirt into front two barrels for a quicker fire up. I let too many of my old clunkers sit too long also.....

10-30-2017, 09:17 AM	#1
KellerMAC Registered User Join Date: Jan 2007 Location: Keller, TX Posts: 143	Start up issue I have a recently rebuilt 72 C10 and it sits during the week and on weekend when I go to start it, I have to pump the gas pedal and turn it over for about a minute before it finally starts up - I drive it through out the weekend and it starts on first turn. Then when I let it sit for the next week, it's hard to start and we go thru the same process again. I have a manual fuel pump on it. Is there anything I can do so it is ready to start after a week long layoff? Thanks, __________________ Texas - Don't Let The Size Scare You!

10-30-2017, 09:22 AM	#2
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,731	Re: Start up issue What carb?

10-30-2017, 02:31 PM	#3
KellerMAC Registered User Join Date: Jan 2007 Location: Keller, TX Posts: 143	Re: Start up issue Rochester 4 barrel - factory carb - 350 engine - recently rebuilt carb and engine __________________ Texas - Don't Let The Size Scare You!

10-30-2017, 02:50 PM	#4
truckster Senior Member Join Date: Jan 2001 Location: Orem, Utah Posts: 7,976	Re: Start up issue Did you replace the filter in the carb inlet, and does it have the flowback preventer valve in it? Also, did you set the float level according to the instructions in the rebuild kit? __________________ I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson

10-30-2017, 02:53 PM	#5
beadblaster Registered User Join Date: Oct 2016 Location: Grand forks,bc Posts: 141	Re: Start up issue Leaking fuel plugs on bottom of carb. Common problem.

10-31-2017, 01:21 PM	#8
Toms67 Registered User Join Date: May 2016 Location: Sackets harbor ny Posts: 282	Re: Start up issue Is the Axcelerator pump working? When you pump it. Did you look in the carburetor and see if it was getting gas? With it not running.Sometimes they dry out. And when you get them wet again. it might work for a while.

10-31-2017, 02:45 PM	#10
LSSierra Registered User Join Date: Feb 2017 Location: Jacksonville, NC Posts: 29	Re: Start up issue Wow my 71 with a Q-Jet also does the same thing. Where is the best place to start troubleshooting? __________________ -1987 GMC Sierra Classic 5.3 LS - -2001 Toyota Camry 175k -

10-30-2017, 02:53 PM	#12
randy500 Account Suspended Join Date: Jul 2016 Location: Tacoma, WA Posts: 6,873	Re: Start up issue Fuel pump is probably leaking fuel back to tank and has to refill line and carb, how old is the fuel pump. You can check this by removing the line and seeing how much fuel is in it. There is a check valve in the pump that when operating correct prevents drain back.

10-30-2017, 03:54 PM	#13
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,731	Re: Start up issue Is your divorced choke new too? Did you clean out the crossover in the intake during the rebuild?

10-31-2017, 03:17 PM	#14
demian5 Registered User Join Date: Aug 2016 Location: Lake Forest, CA Posts: 2,177	Re: Start up issue I believe this is just part of owning a carburated vehicle. We are all spoiled with fuel injection and all these bells and whistles. Yeah this is an issue that can be fixed, but its so common of carb vehicles that its almost like a theft deterrent! __________________ "Work hard, use your vacation days." 1970 C15 GMC Long Bed 1986 C20 Scottsdale 1983 K2500 Sierra Classic Suburban 6.2 Instagram: C10sofOC

10-31-2017, 08:37 PM	#15
garyd1961 Registered User Join Date: May 2016 Location: Henderson NC Posts: 975	Re: Start up issue You could install an electric fuel pump. It would pump fuel up to the carb before the motor turns over.

11-01-2017, 07:48 AM	#16
Zogbert Registered User Join Date: Feb 2008 Location: Falcon Beach, Manitoba Posts: 37	Re: Start up issue Had the same issue. Replaced the fuel pump, and that ended the problem. __________________ 1972 Chevrolet C-10 "Ba-Lou"

11-01-2017, 12:11 PM	#17
bandit0067 Registered User Join Date: Aug 2017 Location: South of the Mason Dixon Line Posts: 61	Re: Start up issue I would bet the fuel plugs are leaking the bowls dry when sitting the short time. Then the fuel pump takes a bit to fill the bowls back up. If you want a quicker start, the bowl air vent tube, yes, that 1/4 inch "tube" that is slanted back towards the breathed stud, on top of the carb, you can squirt a few shots of fuel directly into the bowls. And then maybe a small squirt into front two barrels for a quicker fire up. I let too many of my old clunkers sit too long also.....



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