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Acceleration but no idle. Carb prob?
#1373265 Fri Aug 14 2020 01:49 AM
Joined: Jul 2019
Posts: 41
M
morerog Offline OP
Wrench Fetcher
This topic must appear somewhere on here but I can't seem to find search results.

1951 Chevy 3600 216
Rochester B Carb

New fuel pump installed last week and everything was great until yesterday. Truck sputtered and stalled but quickly recovered by pumping the accelerator and I made it to work. End of the day It restarted and I made it home with no issue. Today same story... started right up, went to work okay but coming home it sputtered a bit then stalled, and now will not maintain an idle.

It restarts fine. Pumping the accelerator pedal keeps it going but it stalls and stops when letting of the gas to idle.

If anyone can suggest a diagnosis page I'd be glad for some direction. If you have a good inkling about the problem I'd like to hear your theory as well.
Thanks,
Rog

Re: Acceleration but no idle. Carb prob?
morerog #1373269 Fri Aug 14 2020 02:51 AM
Joined: Nov 2002
Posts: 2,068
C
Carburetion specialist
(1) Defective electronic conversion in the distributor
(2) Burr on points changing both dwell and timing
(3) Partial clog of idle circuit in carburetor.

Jon


Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify
If you truly believe "one size fits all" try walking a mile in your spouse's shoes!
[image]http://www.thecarburetorshop.com/Avatar.jpg[/image]
Re: Acceleration but no idle. Carb prob?
morerog #1373286 Fri Aug 14 2020 11:25 AM
Joined: Mar 2005
Posts: 1,716
R
Shop Shark
Gonna choose (3).

When changing the fuel pump, you might have had some trash enter the line and make it's way to carb and settle in the idle circuit.

Re: Acceleration but no idle. Carb prob?
morerog #1373298 Fri Aug 14 2020 02:07 PM
Joined: Mar 2014
Posts: 1,705
J
Shop Shark
I'll side with Roy...particularly if there's no filter between the pump and Mr. Rochester. It is possible even though the pump is new that some junk was inadvertently left inside when it was assembled. Have you had previous trouble with the carburetor and idling?


Jon

1952 1/2 ton with 1959 235
T5 with 3.07 rear end
Re: Acceleration but no idle. Carb prob?
morerog #1373309 Fri Aug 14 2020 03:00 PM
Joined: Feb 2004
Posts: 21,205
H
Boltergeist
Here's a sneaky trick that has worked pretty often for me. Open up the idle mixture screw a couple of turns, then rev the engine up close to cruise RPM and either close the choke or clap your hand over the top of the carb. Do this several times. If there's a tiny bit of debris stuck in the idle circuit, the quick shot of high vacuum will draw liquid gasoline through all the passages in the carburetor and maybe flush it out. If it works, fine- - - -readjust the idle mixture and press on. If not, you're going to have to open up the carb and put high volumes of air through every passage to clear the clog.

I hope you didn't use thread tape on any of the fittings of the new pump- - - - -tiny slivers of that stuff love to clog carburetor passages!
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Acceleration but no idle. Carb prob?
morerog #1373315 Fri Aug 14 2020 03:24 PM
Joined: Sep 2009
Posts: 321
G
Shop Shark
Jerry, do you recommend using any type of sealant on the fittings between the fuel pump and carb inlet?


-Patrick
1953 Chevrolet 3100
261 / 4-speed / 4:11 / Commercial Red

Re: Acceleration but no idle. Carb prob?
morerog #1373322 Fri Aug 14 2020 03:42 PM
Joined: Nov 2002
Posts: 2,068
C
Carburetion specialist
Not Jerry, but NO! on the sealants. New fittings will seal. If you absolutely certainly cannot sleep at night if you didn't put something on the threads of the fittings, then 1/2 drop of blue loctite.

Jon.


Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify
If you truly believe "one size fits all" try walking a mile in your spouse's shoes!
[image]http://www.thecarburetorshop.com/Avatar.jpg[/image]
Re: Acceleration but no idle. Carb prob?
morerog #1373324 Fri Aug 14 2020 03:58 PM
Joined: Feb 2004
Posts: 21,205
H
Boltergeist
Brass fittings with pipe threads in aluminum castings shouldn't require any type of sealer. Just don't overtighten them and crack the casting. A long time ago, I used to use a product called "Leak-Lock" which was designed for high pressure refrigeration fittings. It was a thick liquid that resembled blue Loctite. Using sealer on fittings that operate at the pressure of carbureted fuel systems is pretty much redundant.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Acceleration but no idle. Carb prob?
morerog #1373345 Fri Aug 14 2020 06:53 PM
Joined: Jul 2019
Posts: 41
M
morerog Offline OP
Wrench Fetcher
Thanks all;
No troubles previous and I first also thought debris upon replacing the fuel pump.
And no to tape thread.
I'll try my luck at the suggestion from HotRod
Thanks again!

Re: Acceleration but no idle. Carb prob?
morerog #1373346 Fri Aug 14 2020 07:09 PM
Joined: Mar 2014
Posts: 1,705
J
Shop Shark
Re: the thread sealer question...please remember your fuel pump should not produce more than 4 psi...5 at the very most and 2.5 is in my experience just perfect for a 235 or 216 with a 1bbl carburetor. You aren't dealing with the same 50 to 80 psi your city water supply provides.


Jon

1952 1/2 ton with 1959 235
T5 with 3.07 rear end

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