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Edwin 05-10-2010 12:47 PM

hard starting when engine is hot
I got my engine finished and adjust the carburetor today and went for a ride.
I encountered a problem.
The engine will not start when hot. Cold no problem. The car runs good on the road, no hesitation.
Engine is a 1955 plymouth 259 poly engine (P27), just ready overhauling to original specifications. Set timing to 6 degrees advance.
The carburetor is a Carter WCFB 4 barrel carburetor, type 2253S, with automatic choke. The choke operates fine, heat control valve in the exhaust is operating excellent. Carburetor has been cleaned a week ago and has new valve needles, gaskets etc. complete overhaul set installed.

When the engine is hot and I try to start, I have a good cranking engine, have enough fuel going to the carburator, have a good spark (at least I can see one when I took the spark plug out).
I tested to start the hot engine after 1 minute, no problem. After 10 minutes or so, won't start. First I didn't touch the gas pedal. After that I pumped in some start.

Thought of perhaps overflowing gas from heat expension into the intake.
Let engine cool down. Heat up again and start after 10 minutes of rest.
Tried to start with pushing the pedal very slowly to the floor before starting so vapour of the overflowing gas could get out. cranked for about 1.5 result.
adjusted the Float setting specification: prim: 1/8" lowered by 0.027", secondary 3/16" lowered by 0.02". Drop primary 5/8", sec.: 11/16" . I did not readjust the drop after adjusting the level.
This didn't help.

Can anyone help me on this problem?


DoubleVision 05-10-2010 01:04 PM

Improve the grounds. Run a ground from battery to block, from block to frame.

T-bucket23 05-10-2010 01:23 PM

Carb may be leaking down when you shut it off, flooding the engine.
Try holding your foot on the floor and see if it will start or take a look down the carb throat to see if fuel is leaking down when it is off.

Edwin 05-10-2010 02:41 PM

I have a ground cable directly to the engine block. As this is an old car (1955 lots of rusty joints) I have every part, fenders etc. ground attachment places cleaned, copper based grease in between, and measured for resistance.
The starter is underneath the engine, the starter solenoid is mounted on the side of the fender. Even when I tested with the hood opened, and let it sit for 10 min. it wouldn't start.

I just did some tread reading on this topic. I did find 4 things.
1) Carter carburetor has heat starting problem
2) plug inside the carb tends to leak ( do not know which one)
3) heat leak from the intake to the carburetor. I did floor the pedal when starting, with no result.
4) timing to much off. (on this point, I checked timing when the engine was just warmed up and hot, no difference. Mechanical advance in the dif works as higher rpm will advance more). specification is 4 degr advance (1955 fuel) modern fuel should have a little more advance I think (run 95 octane).

Do you know more about leaking fuel into the intake, how to check and what to do about it.

There are some pictures of the carburetor and engine bay in this link

Edwin 05-10-2010 02:48 PM

Could it be that the choke is in wrong opening position?
It was wide open when I tried to start when the engine was hot.

I guess when the engine is flooded by overflow, I should not appear when I stop the engine and hold down the pedal (air filter removed). This will allow the fuel to evaporate like mentioned by T-bucket23. But what is causing it. Were cars that bad in 1955 or people just that patient back then they could wait 1 hour to let the engine cool down...LOL

Edwin 05-11-2010 12:43 PM

Are these wood spacers ready available or do you make them yourself.
If I place a spacer between the carb and the intake I would need some longer studs. Any address where to get them?
I live in the Netherlands. Everything for my car is not available here, so has to come from the US.

technicaltom 05-11-2010 01:21 PM

Hi Edwin. I live in Cork Ireland . and I buy from Jegs -Summit-Speedway-Competition Products .In that order.and have never had a complaint with The Chevy parts in my case or the delivery time, usually less than a week.
In my experience hot start problems are usually Carburetor related .I would start with the float level then have a good check of all the vacuum pipes.
I am assuming that the engine is cranking at the correct speed .

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