1963 Hard Cold Start

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Choke not engaging.
 
How long has it been sitting?
 
Choke may not be closing/properly set, or accelerator pump may not be working when you pump the accelerator pedal before starting, or spark could be weak. On mine, I find that it starts best if I pump the pedal 2-4 times first then hold the pedal down about half way until it catches.
 
BillNap said:
What are some causes of hard cold start on my '63 with a 390-4 bbl?
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Describe what you call a hard start. I have a 292 4BBL and a mechanical fuel pump. Birds were notoriously hot runners. When they sit for a short time after shut down, somehow, the fuel either escapes from the bowl or is forced back and must have a lot of pumping to fire. I must pump for quite some time to ignition during cold starts. You could experiment with an electric fuel pump (they're cheap) install it and then try turning on the ignition for a few moments (without engaging starter) before attempting to add fire. (I am assuming you do your own work). Also, you can check your fuel pressure produced by your mechanical FP for spec pressure during start. Just suggestions.
 
4VE said:
Describe what you call a hard start. I have a 292 4BBL and a mechanical fuel pump. Birds were notoriously hot runners. When they sit for a short time after shut down, somehow, the fuel either escapes from the bowl or is forced back and must have a lot of pumping to fire. I must pump for quite some time to ignition during cold starts. You could experiment with an electric fuel pump (they're cheap) install it and then try turning on the ignition for a few moments (without engaging starter) before attempting to add fire. (I am assuming you do your own work). Also, you can check your fuel pressure produced by your mechanical FP for spec pressure during start. Just suggestions.
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The only problem I have with that is nothing is lubricated before firing. It's better to have several turns of the crank to build up oil pressure before it fires off. learned that from an engine builder who built race car engines. That's why they have a starter switch and a separate ignition switch. Crank it until the oil light goes out and then pump the throttle to fire it up. The worst thing you can do to an old cold engine is not building up the oil pressure before firing off. These are not new cars which are designed to fire at a turn of the key. If you have any knowledge of the old WW II rotary engines they spewed oil and clanked until they warmed up and then performed.
Instant start-up may be satisfying but could shorten the life of your engine.
 
Lots of folkslore abounds. A cold cranking issue is not the same as a "hot soak" issue; lots of 60's cars using modern gas are notoriously hard to start within 20-30 minutes of a "hot" shutdown. When a hot enigne is shut off the underhood temperature spikes and old carburetors will boil the fuel (e.g. percolation - (just like an old coffee pot) and put raw gas out of the nozzles that sits on the intake runners until it evaporates. Try to start the car before that evaporation occurs (about 30-45 minutes) and you are starting a "flooded" car - so cold start procedures apply - like holding the accelerator on the floor and "feathering" the gas pedal to move the car for a short time. You can determine this several ways after shutting down a "hot" car:

1. Look down the carb throat to see if fuel is dribbling down them
2. Use a cheap Harbor Freight IR temp gun and "shoot" the bowls, any temps north of about 140* with modern fuel is a problem.
3. Listen for the sound of fuel boiling in the carb.

Most classic cars are not driven enough for cold engine starts to produce unacceptable wear...
Moreover, most cold start wear is because of the rich fuel mixture when first started; the excess fuel washes the oil off rings and cylinder
walls. So, delaying firing up the engine is minimal help. Aircraft engines are different beasts entirely.
 
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Frankie the Fink said:
Lots of folkslore abounds. A cold cranking issue is not the same as a "hot soak" issue; lots of 60's cars using modern gas are notoriously hard to start within 20-30 minutes of a "hot" shutdown. When a hot enigne is shut off the underhood temperature spikes and old carburetors will boil the fuel (e.g. percolation - (just like an old coffee pot) and put raw gas out of the nozzles that sits on the intake runners until it evaporates. Try to start the car before that evaporation occurs (about 30-45 minutes) and you are starting a "flooded" car - so cold start procedures apply - like holding the accelerator on the floor and "feathering" the gas pedal to move the car for a short time. You can determine this several ways after shutting down a "hot" car:

1. Look down the carb throat to see if fuel is dribbling down them
2. Use a cheap Harbor Freight IR temp gun and "shoot" the bowls, any temps north of about 140* with modern fuel is a problem.
3. Listen for the sound of fuel boiling in the carb.

Most classic cars are not driven enough for cold engine starts to produce unacceptable wear...
Moreover, most cold start wear is because of the rich fuel mixture when first started; the excess fuel washes the oil off rings and cylinder
walls. So, delaying firing up the engine is minimal help. Aircraft engines are different beasts entirely.
Click to expand...
All very valid points. The modern gas especially with ethanol has a lower flash point and evaporates much faster than pure gas. Also Premium fuel also has a higher flash point to prevent pre-ignition ping. From what I've seen non ethanol gas has a higher octane rating to prevent pre-ignition which can be damaging. But that doesn't solve the cold start issues.
 
Keep in mind that with today's ethanol laced gasoline vapor lock can be an issue during hot start up, but that's a whole different subject. It’s a trial and error type situation, that's part of the fun of owning a classic car, tinkering around and hopefully figuring out a fix. On my 1955, Thunderbird I came up with a starting procedure that works best for my car.


Engine Starting Procedure​

Cold Engine - Sitting Overnight - Sitting For A Few Days

1 - Do not touch the accelerator; crank the engine over for 5 seconds.
(This not only fills the fuel filter bowl with fuel, it also builds up oil pressure)

2 - Slowly push the accelerator pedal to the floor and then slowly release the accelerator pedal.
(This closes the choke assembly and primes the carburetor with fuel)

3 - Do not touch the accelerator; crank the engine over for 5 seconds once again. If the engine starts, rev the engine once slightly. If the engine did not start, depress the accelerator 3 times, but only ¼ pedal travel each time.
(This primes the carburetor with additional fuel, but keep in mind, T-Bird engines flood easily)

4 - Crank the engine over once again and when the engine starts, rev the engine once slightly.

Warm Engine - Sitting Less Than An Hour

1 - Do not touch the accelerator; crank the engine over and when the engine starts rev the engine once slightly.

Warm Engine - Sitting More Than An Hour

1 - Depress the accelerator pedal ¼ pedal travel and hold it in that position. Crank the engine over and when the engine starts rev the engine once slightly.

doug7740
1955 Thunderbird Blue
 
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