Carb Help Needed....

Houston Rodder

Houston Rodder

Member
My A was backfiring between shifts and I felt it was running a little lean. Therefore, I thoroughly cleaned the carb with chem-dip and carb cleaner. I put it back together like I have done before and made sure all the needles and jets were clear. I reinstalled the carb and the vehicle started right up. It ran for about 20 seconds and died. When it ran for the 20 seconds it ran smooth and acted appropriate. Now, I can not get it to re-start. What do you guys think? I have a 1/2 tank of fresh gas, the fuel line is free flowing (Just checked), and fuel lever is "on."
thanks
 
IF the new non-starting problem is even carb related, it has to be blockage...Assuming you got the screen when you cleaned it out I'd use compressed air in all passages. If air flows, gas will flow. If gas flows it should at least fire.

Check spark too. Coincidences happen.
 
If you have flow down to the carb, I would think maybe the float valve is stuck closed, tap the float bowl gently,added you may see a rush of fuel at the glass bowl when you do this.
 
Brian T said:
If you have flow down to the carb, I would think maybe the float valve is stuck closed, tap the float bowl gently,added you may see a rush of fuel at the glass bowl when you do this.
Click to expand...

Thanks, when I re-installed it did hang open and spill gas. I tapped the bowl and it stopped flowing.
I have now taken off again and blew w/ compressor through all the openings and it appears to be free from obstruction.
Ignition?
 
Points, Timing? I drove mine to the store after I first got it., it ran fine I came out and it woukld not start. The non popout wire had finaly given up, Poorly previously repaired. Do you have a pop out? I here they can cause weird issues.
 
I had a similar issue. It turned out not to be fuel related. I replaced the modern distributor plate with the condesor and points on the same plate inside the distributor so I'm not sure which was faulty, but it started and ran perfectly after that. Smurkey is right sometimes coincidences do happen.
 
Hi Houston,

This is as old as perfect horse collar adjustment among old blacksmiths who were the first auto mechanics in all of America's rural areas.

They knew the combustion chamber is the "only" place where the buck stops & did not have time to play around.

For the next three (3) weeks or so, hobbyist can check gas flow from gas line, spark at points, tire pressure, bumper height, coolant level, paint on the axle housings, spark at coil wire, toe-in, fan belt tension, etc., etc. & never find the non-starting problem.

Please try this very simple Combustion Chamber Test:

A. Fuel Problem Test:

1. Have a spark plug wrench handy.
2. With hood open, gas line valve open, choke the carburetor, & with switch "OFF" allow engine to rotate about 12 revolutions with your starter or crank.
3. Immediatelty remove plugs & look for plug tips "wet" with fuel.
4. If plugs wet, fuel getting into "combustion chamber" where it "really" counts.
5. If plugs dry, fuel "not" getting into "combustion chamber" where it "really" counts -- dry plugs indicate a definite fuel starvation problem which cannot be overlooked.

B. Electrical Test:

1. Now that plugs are out, turn plugs on sides, & ground the plugs.
2. Turn switch "ON" & crank engine several revolutions.
3. Plugs spark with a "good" spark, wonderful.
4. Plugs don't spark, this electrical problem cannot be overlooked.
5.. Good electrical test for plugs, points, condensor, & the often forgotten distributor body.

Now you know where to start looking because you already know what the "combustion chamber" "really" needs -- fuel mixture & spark.

Will also come in handy a few years from now when starting problems re-occur.

Let us know what you find -- many I'm sure want to assist.
 
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OK, thank you for the suggestions. I did a spark plug test and I am now only getting spark to the front two cylinders. I believe the plugs all had wet tips but it is difficult to tell because I am not sure how much was already there.
I believe I have a spark problem what next?
 
Disclaimer... I didn't read thoroughly all the above posts so if this was said previously I apologize.
"90% of A fuel problems are electrical" :)
 
Hi Houston,

1. If plugs are previously wet, & you are not sure about this particular "wet" plug test, please dry plugs with Q-tip or paper towel & try again -- note: gasoline on plugs will evaporate immediately; but oil mixed with gas will linger a while longer -- finding fuel wet plugs immediately after cranking is most important for combustion -- if poor lighting, your nose can be used to smell the gas.

2. Fire only to the 2 front plugs -- first swap plugs 1&2 with 3&4 & see what happens -- strong possibility 2 front plugs were not "properly" grounded as opposed to bad 3&4 plugs -- or tops of 3&4 plugs are grounded & sparking at tops & bottoms of 3 & 4 plugs are not sparking.

3. If plugs 3&4 are "definitely" not getting spark, do a multi-meter OHM continuity test on #3 & #4 spark plug diodes on the distributor body -- should have continuity in distributor body for all 4 plugs.

And please report back.
 
OK, Now my wife is home and I have re-checked the spark. I am getting spark in all four. Additionally, I can keep it running on starting fluid. Therefore, it must be a gas problem. I have re-cleaned the carb three times and all needles and jets are clear and I have run compressed air through them. I must have put something in the wrong place. Does anyone have a blown up view of the carb.
 
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Hi Houston,


1. Please refer to reply #8 again, paragraph B. Electrical Test -- Good spark -- wonderful.
2. Wife is home, wonderful also, give her a hug, most important!"
3 I would definitely go back to paragraph A -- Why?


Well, who really cares if the fuel line has excellent flow; or, if the gas is fresh; or if the gas tank is 1/2 full; or if the engine runs on starter fluid or ether; or, if the carburetor & jets have been thoroughly cleaned & even passed a highly technical CATSCAN Test at the local hospital.

"What" is happening in the combustion chamber?

Are the plugs getting wet? Yes? _______; or No? _______.


Could be a vacuum air leak at manifold/carburetor joint; or air leak between carburetor halves; or at intake manifold; or something else.

Again, think combustion chamber where the buck stops; i.e., are plugs getting wet?


Don't forget to hug your wife.


Let us know what happens with Test A -- wet or dry plugs.
 
Houston,

http://modelabasics.com/carb basics 2.htm

Try this link. Good stuff.

My guess would be the float needle valve. Everything else is "passive" if it is clear, in that as long as gas is in the bowl variations in pressures force the gas into and through the various orifices.

Float tang bent too severely,
Needle valve stuck in seat,
Gas route between inlet to bowl...blow in inlet with bottom of carb, lift and release float, you should feel the on/off of the valve doing its job...if you don't, it ain't.

P.S. I agree with you that if it will run on starting fluid, it's carburetion; not spark/ignition.
 
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Smurkey said:
Houston,

http://modelabasics.com/carb basics 2.htm

Try this link. Good stuff.

My guess would be the float needle valve. Everything else is "passive" if it is clear, in that as long as gas is in the bowl variations in pressures force the gas into and through the various orifices.

Float tang bent too severely,
Needle valve stuck in seat,
Gas route between inlet to bowl...blow in inlet with bottom of carb, lift and release float, you should feel the on/off of the valve doing its job...if you don't, it ain't.

This helps. Thank you
P.S. I agree with you that if it will run on starting fluid, it's carburetion; not spark/ignition.
Click to expand...

This helps. Thank you
 
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