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54 chevy 235 1bbl rochester carb.

  
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54 chevy 235 1bbl rochester carb.

 
jerry68 jerry68
New User | Posts: 6 | Joined: 05/13
Posted: 05/11/13
01:19 PM

Ready to throw in the towel.This engine is in a 49 chevy pick up. It sat two years without running. When it ran it was smooth and quiet and run like a sewing machine,quiet. Well I been trying to get it running. All the long I would crank the engine just to keep it from freezing up . There was some old gas ,maybe 2 gal.I now have about 6 gallons of good gas . new plugs, gapped, checked point gap it's at 16 , it gets spark, I have a new fuel pump, and remanufactured rochester carb. Also put new fuel filter ,kind you can see through. Infact the first one collected some grit so I replaced it with another new one. When I try to start it ,it starts and dies . I have set the idle up but it still starts ,runs 3-4 seconds and dies. I dump gas in the carb , same thing. Its been in the garage all this time . I even thought maybe my tail pipe was plugged by a mouse maybe .Run a rod into the muffler, still no luck. didn;t seem to be a problem there. Wow what can I do short of calling a real mechanic out ?? Any ideas???Thanks.  PS.I also checked to make sure the carb float was freed up and not stuck.  

Steve56chevytruckUK Steve56chevytruckUK
New User | Posts: 42 | Joined: 01/10
Posted: 05/11/13
03:03 PM

Is the choke stuck in the closed position?  

waynep712222 waynep712222
New User | Posts: 48 | Joined: 04/13
Posted: 05/11/13
05:20 PM

ok.... real mechanic here... i have only been one for 33/34 years..

disconnect the ignition coil primary wire so NO SPARK WILL BE CREATED for this test...

disconnect the fuel line at the carb.... extend the fuel line with some fuel hose into a clean, clear.. 2 or 3 liter plastic soda bottle...   have a friend crank the engine for 15 seconds without stopping while you observe the pulses of fuel from the end of the hose into the bottle...    each pulse should be nice and full...   equal to all the others..   you should also have around half a quart of fuel in the bottle after 15 seconds.. this proves the fuel pump, lines, hoses, pickup in the tank are capable of flowing enough fuel...

now.. if you have one of the low pressure fuel gauges... goes from 30 inches of vacuum to 15 pounds of pressure.. hook that to the end of the fuel line and crank for 5 seconds.. you should have instant pressure and it should hold...

sediment in the fuel pump... since most people have the fuel filter between the pump and the carb.. when it actually needs to be just before the pump.. so the pump is protected from crud from the tank and lines...

once verified...

since you know how to remove the top of the carb... i am taking its full of fuel...  thats a model B rochester i am taking...

are you familiar with how carbs work...    i can link you some model B overhaul instructions...

there are 5 circuits in the carb...

idle circuit.. where fuel is pulled up and over thru the passage below the throttle plate... this is limited by the idle mixture screw... and fine tuned by the idle air bleed and idle feed restriction..

the idle transition circuit.. this is fed thru a slot just equal with edge of the throttle plate.. as the throttle opens.. more of the slot is exposed to vacuum and more fuel is pulled thru...  this is also limited by the idle feed restriction and idle air bleeds... but not the idle mixture screw...

the main circuit..  and the idle transition circuit.. above around 1100 RPMs and up thru about 2300 RPMS. both idle transition and main circuits feed the fuel to the engine..

main circuit.. is controlled by the air going fast enough thru the venturi to lower pressure and pull fuel up thru the main jet and over then out of the booster venturi... this is limited by the main jet and high speed air bleed...

there is a power circuit in most carbs.. that bypass the main circuits at lower vacuum when you are going up a hill when engine loads are heavy and manifold vacuum is lower... so there is enough fuel to have a rich air fuel ratio to make some power...

an accelerator pump circuit helps when coming off idle and the throttle plate is opening faster than the air flow can lift the fuel up and over... so it sprays some fuel while the throttle is in motion opening...  there is usually 2 check balls in this circuit.. so the pump on the upstroke can pull fuel in from the float bowl.. and on the down stroke can push it out the discharge nozzle...


the CHOKE... hmm.... this is a blade at the top of the carb..  above the air bleeds .. when you first start the engine cold.. you need more fuel.. so reducing the pressure above the air bleeds causes the fuel to come up faster and causes a richer air fuel ratio for easier starting..    if the choke is stuck closed.. it will cut off too much air and the engine will die, usually fouling the spark plugs...

please check for fuel flow.. as described above...

you could also have trash... spiders... dust. corrosion in the various circuits in the carb... preventing any fuel flowing thru them..

and yes.. i typed all this above..

i was watching nascar on fox and not keeping an eye on the forums. like i should have been...

i do check this forum every few hours...  so do post...

if you get in deep trouble... we might talk..   post what you find...  

waynep712222 waynep712222
New User | Posts: 48 | Joined: 04/13
Posted: 05/11/13
05:22 PM

its also totally possible that the 2 year old fuel has really gummed things up...

fuel stabilizers do actually work...  but not if the good stuff in the fuel has already evaporated...  

waynep712222 waynep712222
New User | Posts: 48 | Joined: 04/13
Posted: 05/11/13
05:29 PM

Idleandtransitioncircuit

64Modelb0003 Jpg

64Modelb0004 Jpg

64Modelb0005 Jpg

64Modelb0011 Jpg  

jerry68 jerry68
New User | Posts: 6 | Joined: 05/13
Posted: 05/11/13
07:35 PM

Thanks for the reply. No, the choke is free ,opens and closes fine by hand. This is a new re-manufactured carb and was certified to be tested on an engine prior to shipment .  

jerry68 jerry68
New User | Posts: 6 | Joined: 05/13
Posted: 05/11/13
07:42 PM

Wayne thanks for all your time here. This is a new carb. Certified to be tested prior to shipping. I will do the test you suggest . By the way the fuel filter level stays 1/2 full and I'm not seeing any sediment in this filter (the second one I put on } However I agree that the filter should be b4 the pump . So I will do the test to see what the pump is doing . This wont be till next week . I will be unable to do this till next saturday. Again I thank you for taking time to do all this.  

waynep712222 waynep712222
New User | Posts: 48 | Joined: 04/13
Posted: 05/11/13
08:15 PM

i should be around... post what you find jerry..

if all else fails...   log in.. check your messages to the left of where you log out at..  

sedjohn44 sedjohn44
New User | Posts: 3 | Joined: 11/13
Posted: 11/30/13
10:49 AM

Wayne, I only get half pages on the lower part of your post.    I've tried all my computer tools and can't see it all, would love to study this, looks so helpful.

Thanks, John  

sedjohn44 sedjohn44
New User | Posts: 3 | Joined: 11/13
Posted: 11/30/13
10:50 AM

Wayne, I only get half pages on the lower part of your post.    I've tried all my computer tools and can't see it all, would love to study this, looks so helpful.

Thanks, John  

sedjohn44 sedjohn44
New User | Posts: 3 | Joined: 11/13
Posted: 11/30/13
10:50 AM

Wayne, I only get half pages on the lower part of your post.    I've tried all my computer tools and can't see it all, would love to study this, looks so helpful.

Thanks, John  

wayne712222 wayne712222
New User | Posts: 37 | Joined: 10/13
Posted: 11/30/13
02:28 PM

those are actually images like a photograph...

you should be able to right click and open each of them in a new window in order to view them..

or click on them and print image.. you may have to select the scale image button on your print control panel.. so you get it all on one page..


below the bottom most image.. is a slider.. you man move it back and forth and shift the images above into the viewing window..