The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1967 - 1972 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 10-26-2021, 11:17 AM   #1
skidoo
Registered User
 
Join Date: Mar 2015
Location: alberta
Posts: 23
Hard start

On my 72 gm 350 after it sits for about a month it is hard to start. It does have a mechanical fuel pump. Is it wise to dump a little gas down the carb to help it along?
skidoo is offline   Reply With Quote
Old 10-26-2021, 11:25 AM   #2
geunther
Registered User
 
geunther's Avatar
 
Join Date: Apr 2005
Location: Cheyenne, WY
Posts: 742
Re: Hard start

If you did that, I am sure it would fire right up. Mine is a right leg workout of small weight, many reps if it sits for a month
geunther is offline   Reply With Quote
Old 10-26-2021, 12:34 PM   #3
sick472
Registered User
 
sick472's Avatar
 
Join Date: Jul 2015
Location: Sedalia Mo.
Posts: 1,130
Re: Hard start

A shot of gas will help it fire up and it may keep running or not. One of my projects takes a few tries to get it to the point of it supplying its own gas. This tactic, IMO, saves some wear and tear on the starter.

Just be aware that this approach can cause some potential problems like spilled or leaked gas. If backfiring occurs along with spilled or excessive gas...a fire is possible. It is wise to pour the shot into the primaries, not the secondaries. This will help ensure the shot does not set on top of the butterflies and try to leak out the shaft holes in the sides or drop all the gas into the intake at the slight push of the pedal.
__________________
He who is without oil shall throw the first rod. Compressions 8.7:1

1972 C10
1976 C10 (parts truck)
1985 K20
sick472 is offline   Reply With Quote
Old 10-26-2021, 12:59 PM   #4
72c20customcamper
Registered User
 
72c20customcamper's Avatar
 
Join Date: Jul 2018
Location: Catskill Mountains,NY
Posts: 8,053
Re: Hard start

I keep a small catsup squirt bottle to squirt gas in . No spills and you have control of the amount you use
__________________
Mark
72 c20 custom camper Husky edition,
66 SS396 Chevelle 1964 Hawk, 63 Avanti,62 lark
1969 AMX ,
1968 c20 stepside ,85 K20
1977 Suburban sold
68 anniversary.
72c20customcamper is offline   Reply With Quote
Old 10-26-2021, 08:44 PM   #5
HO455
Post Whore
 
HO455's Avatar
 
Join Date: Feb 2016
Location: Portland Oregon
Posts: 10,752
Re: Hard start

Better to use small funnel or the ketchup bottle to fill the float bowl through the vent. A couple of ounces is all that is needed. Much safer than pouring fuel in the bores and less chance of flooding the engine.

Allow the engne to sit for 5 minutes or so after filling the float bowl to allow the accelerator pump to absorb fuel and swell up. Then the accelerator pump is more likely to work correctly.

If you have no other option but to pour fuel in the bores then make sure you hold the butterflies open so the fuel doesn't run out the butterfly shafts.


And always put the air cleaner back on before cranking the engine to prevent a fire.
__________________
Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help.
RIP Bob Parks.
1967 Burban the WMB,1991 S(stink)-10 Blazer,1969 GTO, 1970 Javelin, 1952 F2 Ford 4X4, 29 Model A, 72 Firebird. 85 Alfa Romeo
If it breaks I didn't want it in the first place
The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377
HO455 is offline   Reply With Quote
Old 10-26-2021, 09:09 PM   #6
truckster
Senior Member
 
truckster's Avatar
 
Join Date: Jan 2001
Location: Orem, Utah
Posts: 7,760
Re: Hard start

A shot of brake cleaner in the snorkel will do the same for you. You could use ether, but it's harder on the engine.
__________________
I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson
truckster is offline   Reply With Quote
Old 10-26-2021, 10:56 PM   #7
Mike C
Registered User
 
Mike C's Avatar
 
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 7,709
Re: Hard start

I keep a quart of the 50:1 TruFuel weed-whacker fuel on hand. When a vehicle has sat for a few weeks I remove the air cleaner, dump a cap full of the TruFuel in and crank. Usually have to dump in one more cap and then it will idle. Saves a lot of wear and tear on the starter. And since the TruFuel is a premix it provides some top end lubricant to help with the overly rich temporary mixture.
__________________
44 Willys MB
52 M38A1
64 Corvette Coupe
68 Camaro 'vert LT1 & TH700
69 Z/28 355 12.6's @110
69 Chevy Short Step 4 1/2"/7" drop
72 Jimmy 4WD 4spd 4" & 35's
02 GMC 2500HD 4x4 Duramax
Mike C is offline   Reply With Quote
Old 11-26-2021, 01:08 PM   #8
geunther
Registered User
 
geunther's Avatar
 
Join Date: Apr 2005
Location: Cheyenne, WY
Posts: 742
Re: Hard start

I stumbled onto a possible solution for this for those running the Q-jet. There are fuel filters that have a check valve in them to prevent the fuel from running down back back out of the carb and into the mechanical fuel pump.

https://quadrajetparts.com/short-pap...alve-p-79.html
geunther is offline   Reply With Quote
Old 11-26-2021, 02:18 PM   #9
RustyPile
Registered User
 
RustyPile's Avatar
 
Join Date: Dec 2017
Location: Elkhart, Texas
Posts: 1,512
Re: Hard start

Quote:
Originally Posted by geunther View Post
I stumbled onto a possible solution for this for those running the Q-jet. There are fuel filters that have a check valve in them to prevent the fuel from running down back back out of the carb and into the mechanical fuel pump.

https://quadrajetparts.com/short-pap...alve-p-79.html
Law of Physics: liquid cannot run up hill.. The needle and seat is located slightly above the fuel level in the carb bowl and well above the bottom of the bowl.. If fuel is leaving the bowl not through evaporation, it's because the metering well plugs are leaking..
RustyPile is offline   Reply With Quote
Old 11-26-2021, 02:31 PM   #10
geunther
Registered User
 
geunther's Avatar
 
Join Date: Apr 2005
Location: Cheyenne, WY
Posts: 742
Re: Hard start

Yes, physics involved and agree about meeting wells. Check valve would leave fuel in the filter housing and likely in the fuel line between pump and carb due to the physics of a vacuum when the check valve is closed. Being closed and less exposed to atmosphere, less ability for what fuel is there to be lost due to evaporation. Certainly slower to evaporate.

I suppose there was a reason for the check valves.
geunther is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 06:13 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com