64 ford 4000 gas 4cl ka pow backfiring when cold, then runs.

my old throne in the flesh...my 64 4000 gas 4cyl is acting up again.
new carb, new points, rotor, coil, plugs,wires, good battery, good timing, new gas lines, new gas filter and an in line micro filter to boot.
starts right up.
give it 1 minute, dadaddada pow pow dadada da powpow. dies.
let it sit 1 minute.
starts right up.
same kapow. turn it off.
runs 2 minutes.
kakapow pow.
sit it.
starts....kracckle dadadada pow pow runs for 3 hours like a sweating horse perfectly.
neighbor said bad gas.
tried gas additives. heat, you name it.
high test too.
no change.

any clue?
 

Too many filters and its starving for gas... due to gravity flow, cannot have any restrictions on gas flow.

After one minute, the carb fills up again, and its good to go... till it runs dry... find your fuel restriction.... Its probably the filters, but could be anything, including the float or needle valve.
 
That needle valve will stick closed intermittently. Probably stays open for the 3 hours of good running due to engine harmonics.
 
What is the reason for so many filters? Is your tank rusty?
I think I would fix the root cause and get rid of the band-aids.
If that "pow" is out of the carb, it may also have ruined the floats
in the "new" carb. If the new carb is aftermarket, it may be part
of the problem too. What did you do with the original?
 

cousin used to live at Vanzant. I'm with the "too many filters" gang for starters. That may not be all of it, but it's a start.
 

It apparently has an issue that is cured by an increase in temp. Due to air flow carburetors stay cool. I suggest a careful examination of the distributor wiring, especially the wire from outside to inside.
 

ok,, maybe the carb is flooding.. and as others said, the needle finally starts to seat and then your excessively rich mixture is now down to normal.

I was going on the carb running dry.... and killing it,, maybe it was opposite and creating black smoke and flooding out,, but a cold engine LOVES a rich mixture...

A bad wire normally does not run perfectly for 3 hours and only act up on cold start.
 
updates...

took off micro filter and hit home run with it. ran new fuel line straight from new tank petcock/internal stem filter. my ranch hand just put it in for extra protection. no other reason.
removed air from bowl. no crud in bowl.
used fresh gas from a known good gas station.
tank is clean.
still backfires out the exhaust then dies....when cold.
tapped the float bowl with a wooden mallet thinking a flaot was stuck or a needle was sticking.
starts again and dies again. then 10 minutes later, it runs fine when hot.
we are checking bad igition assy now. only problem is, if it was an igition assy, it would fail all the time. right?

it certainly is linked to a cold engine hot engine. once it heats up, everything works.
if it was wires, plugs, coil, or condenser....wouldnt it backfire always?

we checked the routing of the fuel line to ensure its not resting on a hot portion of engine. it isnt.

carb is new aftermarket, zenith. oem was 60 years old and just fell apart. rebuilt it twice and still leaked. thus, we got the new popular aftermarket carb, NIB.

cold hot is the issue. anything else im missing?
 
i'm going with a lean condition that corrects when it warms a hair.

95% of backfiring i've encountered has been run on / lean. the other were sticking valves.

Both easy to correct.
 
im so friggin embarrassed.
found it.
loose screw on the points. dwell was off. re-set it. runs. thanks guys.
you may start beating me up if youd like. lol.

but im still wondering how it ran great after a while, if the dwell was off!
 
Glad to hear you found the problem and its nice that you let
everyone know what the cause was for future knowledge.
If you still have the original carb, I'd pay the shipping to
use it as parts. My email should be open.
 
(quoted from post at 17:18:32 10/26/17) im so friggin embarrassed.
found it.
loose screw on the points. dwell was off. re-set it. runs. thanks guys.
you may start beating me up if youd like. lol.

but im still wondering how it ran great after a while, if the dwell was off!

Thanks for posting back, and glad that I pointed you to the distributor, LOL. It could have been something as simple as the position of the points changing a little as the plastic block that pushes the points open warmed up.
 
FYI:

If you install a point triggered electronic ignition (hybrid store bought or homebrew) the dwell does not matter a whole lot. Tractors cranks more easily. I used to futz around for 30 minutes trying to get the gap right until I bought a dwell meter.

The point triggered electronics came later. I know, I know, there are trigger units that totally replace the points, but not every gas tractor has an off the shelf reluctor or equivalent. Kluging a trigger work around takes time, but the hybrid unit I use to test gas tractors jumpers in (2-5 minutes) and bypasses the coil and everything but the points. Points last incredibly long. One unit I put in my sisters car kept the points going 70.000 miles until the curved flat spring broke from fatigue. lol

The main thing is you don't have to mess with points for a long, long time unless they get some sort of weather corrosion on them, because they carry very little current compared to a regular coil and capacitor system.
 
the original carb was rebuilt twice by a shop and it still leaked. finnaly, i got it to stop leaking and it kapow-bang powed on me, so i changed carbs. new carb worked for 6 months, now its kapowing. seems the internal specs must be way off or just plain worn out on the ford carb.
btw....this morning, it kapowed again. but, not as bad. so i just let it warm up and it ran after dieing 3 times. weird. seems like all of a sudden my faithful ford is acting up.
royse, let me see if i can find the oem carb. look for email or pm soon.
 
im going to try putting a new coil wire on.
and, seems all this problem started when the oem ford carb got replaced with a zenith.
whats zeniths reputation ??
 
For what my opinion is worth I think the Zenith carburetors are well rated. I cannot remember at the moment but I think the carburetor on my cousin's Super C Farmall may be one or a Carter. No carburetor is good if it gets trash or water in it.

If it ran well for six months and then suddenly went bad I would suspect water or some particles of trash or even some small bits of metal that escaped the cleaning process if it was cleaned after manufacture.

I found that one of the main problems with older carburetors isn't valve seat and needle, float or jets, its wear at the throttle bushings. I rebuilt the Super C carburetor but it still did not run great. I made a new throttle shaft and new bushings and it ran great afterwards. Even a new throttle shaft or choke shaft does little good if the bushings are worn and allow air past the shaft. I also found that the aluminum or pot metal top piece was warped a little and I had to make a special fixture to bend the housing back down so everything was flat.

I have also seen factory rebuilt carburetor jobs that were botched. One had a pinched aux jet tube. Another carburetor on a new GM car had a loose top housing.
 
Bob,

I forgot to add this. Make very sure your intake/exhaust manifold is not warped or the gasket bad. I think this will also cause some of the symptoms you listed. Do you know how to test it without removing the carburetor or manifold?
 

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