Trouble starting after warm

[79k30guy]

So I've developed a bit of an issue. I'm having trouble starting back up after the trucks been sitting 5-20 minutes.  Like the fuel drained out of the carb?    The truck lights off cold no problem, warms up good, but after I park and run into the store for a few minutes, it has trouble starting.  Or will start but dies after a few seconds and is a pain to get running again.   ...it always does, eventually. Just takes a few minutes of cranking. 
  Any thoughts guys?
Thanks

Small block 400 with Holley 650 electric choke.

[78BIG-TEN]

What do you do to restart it,just turn the key,push the gas pedal down a bit while cranking or floor it while cranking.Need more info

[VileZambonie]

Holley 650 electric choke

 - Check your ignition system, set your timing, check your choke and float circuits for starters

[79k30guy]

Yes just feather the gas a little and crank it over and after a minute or so of about 3 trys it starts. 

Thanks Vile I will start there next chance I get

[jg1977c20]

try starting it without feathering the gas - mine will start with just the turn of the key -

check timing , fuel flow when hot ( could be fuel pump wearing down when hot) , maybe time for a carb rebuild or your idle mixture is too lean just to give you some places to look .

[enaberif]

What are you using for a insulator between the carb and manifold?

[1979cheyenne]

Watch choke as engine warms up to see if it is adjusted properly, maybe adjust it and restart when it's hot, some things I've had to play around with on mine

[fitz]

Even if it don't start, just step back and enjoy the view.
That is a great looking truck.
I'm sure Vile will get the problem sorted out for you.

[rich weyand]

The choke cools off faster than the engine, because it's just this little pod on the side of the carb and the engine has huge thermal mass.  So, stone cold, they are at the same temperature, no problem.  Shut it off for a minute, and restart it, they are both at operating temperature, no problem.  Have it off long enough for the choke to cool off and the engine to still be warm, they are mismatched and the mixture is too rich for an easy start.

Be glad it isn't an early sixties Chrysler.  If you shut them off for between 15 and 45 minutes in the winter and tried to restart them, they would flood, and that was it, you weren't going anywhere for a while.  I clipped a bulldog clothes pin to a battery cable, and if I was gone for 15-45 minutes in the winter, I would have to remove the air cleaner cover, clip the choke open with the clothes pin, start it and let it (and me) warm up for 5 minutes, then go out and remove the clothes pin and replace the air cleaner cover.

Anyway, mine's the same way.  C'est la vie.

[srozell]

Thanks Rich,

That's the first time I've seen the problem explained, and it makes perfect sense now that you've said it.

[rich weyand]

OK, now I'll give you a fix for it.  Take the choke hot wire off the oil pressure switch and connect it directly to the ignition hot.  Keep track of the time when you shut it off, and note the time when you get back.  If it is in the 5-20 minute range that gives you trouble, turn the ignition on, but don't try to start it.  Just sit with the ignition on for a couple minutes, warming up the choke so it and the engine match.  Now depress the throttle once and release, and hit the key.  Instant start.

[srozell]

The current from the battery is enough to warm up the choke?

[rich weyand]

I am assuming electric choke here.  You have to understand how it works.

Basically, inside the little black cap is a spring like a clock spring, wound around and around.  The outside end is connected to the cap, the inside end is connected to the choke actuation shaft.  There is a wire connected to each end of the spring.  At rest when cold, the spring has the choke engaged.  When you start the engine, the oil pressure comes up and turns 12V onto the spring, which warms up from being heated by the current passing through it.  As it warms up, it wants to unspring, and so it turns the shaft and deactivates the choke.  It will stay warm as long as current is passing through it.  Park the car, turn off the engine, the current stops, the spring cools off, and as it does it takes up its normal shape, and turns the shaft activating the choke again.  You adjust the choke by rotating the cap, which sets the position of the other end of the spring.

Now, if you have a problem with the choke cooling off too soon, so that from 5 minutes to 20 or 30 minutes after being run, the engine is hard to start because the mixture is too rich (too much choke), it's because the engine is still warm and doesn't need any choke, or at least not so much.  One way to fix it is to connect the choke directly to ignition (NOT battery), so that, if the key is on, even though the engine is not running, it will heat up, you can get in and turn the key on without starting the engine for a bit.  Get your seat belt on, put on your driving glasses, light up a cigar, and THEN, once the choke spring has warmed up and started turning the choke off, then you start the engine.  Should fire right up.

That's how mine is hooked up.  Sometimes I remember, sometimes I don't.  When I remember, it starts no problem.  Of course, in the winter it helps if you have heated seats, because you can turn those on right away so you aren't freezing while you wait for the choke to come up to heat.

[srozell]

Got it, thank you!