doesn't start when warm

[ChrisCoccia]

Okay, I rebuilt my carburetor, and made sure there were no vacuum leaks anywhere. Now it starts great when cold, runs and drives great, but if I shut it off and try to start again-no dice. I tried turning it over without touching the gas, pumping a fewtimes, and holding the pedal down, no help. If I give it a squirt of starting fluid it cranks right up, but I don't think that is a practical solution long term.

[Reg Evans]

Could you have left the ball out of the bottom of the accelerator chamber. If so the pump will not build pressure and squirt gas into the engine when starting.

[ChrisCoccia]

I know I put that small ball in there, b/c I had to monkey around with the clip that holds it in for a while before I got it locked in. The big ball goes in under a screwed in plug, so I don't know how that could go anywhere. I blew out all the passages and jets several times with air.

[Reg Evans]

Does the accelerator pump plunge down into the carb when you open the throttle linkage to full throttle? I'm assuming it's not squirting into the engine when you do this.

[Merle Coggins]

I have a similar problem with my truck, but I learned the trick. I probably need more carb adjustment but this works for now. My truck will start fine cold even without using the choke, but once warmed up it'll crank all day and won't fire. I've learned that if I pull the hand throttle out slightly (because it's kind of hard to hold slight throttle pedal and push the starter too) then hit the starter it'll fire right up. As soon as it fires I push the throttle cable back in.

I suspect that my idle circuit is too rich but I havn't had any luck tuning that out yet. I'll have to keep messing with it.

Merle

[MBF]

Are you using good quality battery cables rated for 6 volts? If they've got corrosion inside or you're using the thinner batt cables for 12V that'll cause excessive amp draw and result in a shortage of oomph. I'd then check your batt voltage at the battery and starter-you may have excessive power draw at the starter during hot starts. I'd check the amp draw at the starter and make sure all connections on the batt, starter, ground, and chassis to engine ground are clean and tight. You may also be be experiencing fuel vapor lock when hot. Is the needle valve and seat in good shape and properly adjusted? Is the heat shield on your fuel pump intact? Had this problem w my 36 plymouth. Mike

[greg g]

It sounds counter intuitive but a lot of hot start problems are caused by a float level that it set too high. This allows for fuel to perculate out of the bowl and into the manifold where is puddles and causes a flooded start condition. Check to see if there is any raw gas around the throttle plate pivot pin. If so this, indicates this may be the problem. So try to do the hot start by holding the gas peddle at WOT while cranking, as you would while trying to clear a flooded engine.no pumping before hand. I have set my floats (have dual carbs) a bit lower (tab bent toward the front of the car).

Even at the factory setting with high underhood temps todays fuel formulation can expand enough to over flow the bowl. Depending on how long you sit, it can cycle several times as the residual pressure in the line from the from the pump will refill the bowl again and start the cycle over.

Check your oil and see if you have any gas smell from the oil. this will also confirm this condition, as the raw fuel will seep by the rings and into the sump. If you do smell gas in the oil change the oil.

I personally don't believe in vapor lock unless you are talking about at the fuel pump but we can go over that later, (if vapor can block a fluid under pressure, how can we bleed our brakes) So resetting the float bowl is quick and easy to do and just as quick and easy to undo if its not the problem.

One other thing to try is to set your timing a bit advanced from the factory spec. Todays fuels have a slower flame front than old gas, think whoomph, instead of bang. As such a bit of anticipation of TDC (where bang works best) is needed at idle/start. I am running about 4 BTC.

Keep us posted.

[ChrisCoccia]

I figured it out! I took the top off the carb and realized that the accelerator pump was doing exactly nothing! Apparently after 60 years the spring has become shorter/compressed, so I gave it a stretch and suddenly I had a spray of gas into the throat of the carb when the throttle is opened that I didn't have before. I put it back together and the problem is solved. It starts right up every time! Thanks for all your help.

[grey beard]

By the bye, gents, our Carter B & B carbonaters have TWO ball check valves inside, there. One is held in by a C clip and the other will fall out when you remove the pump plunger. Mebby one is inlet valve and the other discharge, what?

We talked about a lot of stuff on this thread already, and some of it may be confusing to other folks. The accelerator pump only squirts fuel into the carb throat when the throttle is depressed. The fuel pump may be a culprit where questions of vapor lock - usually only a hot summertime problem - is encountered. The two pumps are NOT the same.

I agree with MB about cranking rpm. Yeah, these engines will turn over and catch, and even run, but when you are spinning 'em over with the starter like they're supposed to spin, a lot of things change. Carb vacuum is considerably higher, fuel being pulled into the cylinders is at a higher volume and better vaporized, AND you likely have hotter spark, what with the extra available voltage left over from the starter circuit for the ignition system. Sure does make for a happier engine - and a much faster start each time on crank-up.