Hard Starting When Hot

Hey all,

My stang starts up fine when cold, but when hot requires some extra effort on the throttle...I want to address this problem. I think it might be vaporlock but not too sure. Any ideas/solutions would be great. Concerning my ignition I am running points, Accel coil, new starter, NGK plugs, and single barrel carb. Thanks in advance. -Jon

Do you still have the spacer below the carb the has coolant running through it?
If you don't, this could cause vaporlock since the exhaust is right below the intake.

8) you are probably getting flooding due to fuel boiling, it is a common problem in the hotter climates. a heat shield will help insulate the carb from the heat of the exhaust manifold and help prevent fuel boiling.

Is a heat shield the same thing as a carb spacer? What works best for the stock single barrel carbs?

You may not want to hear this, but installing an electric fuel pump will clear up any hot starting issues. You flip the pump on before starting and it fills the carb with fresh fuel and you're good to go. The standard Holley red pump will be more than enough. You don't need a regulator with the red pump.

JT81stang":wdhavs26 said:

You may not want to hear this, but installing an electric fuel pump will clear up any hot starting issues. You flip the pump on before starting and it fills the carb with fresh fuel and you're good to go. The standard Holley red pump will be more than enough. You don't need a regulator with the red pump.

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Are you suggesting REPLACING the stock fuel pump, or adding the electric pump in addition to the stocker?
Joe

I've seen it done both ways. Some guys install one to help the mechanical pump and some remove the mechanical pump and install only the electric pump.
But remember, electric pumps are better at pushing fuel than pulling fuel from the tank so mounting it as far back near the tank is the key. I usually mount them on the frame where it kicks up above the rear diff.

Hasn't been too hot lately in SoCal. It runs hot when it's too lean. Also, you might have too much advance. Back it off a touch. You can route the heater hoses away from the carb. Also some guys here have put some kind of heat shield - metal flap barrier - between the exhaust and the carb.

if you have the mounting place/spacer with the heater hose nipples, make sure the hose is connected AND that you get free flowing coolant through the heater core so the base stays a constant warm but not too hot temperature.

JT81stang":11er3ppg said:

I've seen it done both ways. Some guys install one to help the mechanical pump .....

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Ahhhh! I was wondering if the valving in a mechanical pump would allow the fuel to pass when it is stopped; apparently it can?
Joe

Lazy JW":2h5i3o2k said:

JT81stang":2h5i3o2k said:

I've seen it done both ways. Some guys install one to help the mechanical pump .....

Click to expand...

Ahhhh! I was wondering if the valving in a mechanical pump would allow the fuel to pass when it is stopped; apparently it can?
Joe

Click to expand...

8) yep, does pretty nicely too.

slightly off topic.
What if you sport the elec. pump with the mech. pump and the diaphragm goes out in the mechy? pan full of gas but the carb still gets enough fuel?

rbohm":1mqmm0py said:

Lazy JW":1mqmm0py said:

JT81stang":1mqmm0py said:

I've seen it done both ways. Some guys install one to help the mechanical pump .....

Click to expand...

Ahhhh! I was wondering if the valving in a mechanical pump would allow the fuel to pass when it is stopped; apparently it can?
Joe

Click to expand...

8) yep, does pretty nicely too.

Click to expand...

Thanks, that would be a pretty easy way to have a backup pump; just keep a short piece of fuel line handy to bypass the mechanical pump if needed.
Joe

'68falconohio":uijwhil5 said:

slightly off topic.
What if you sport the elec. pump with the mech. pump and the diaphragm goes out in the mechy? pan full of gas but the carb still gets enough fuel?

Click to expand...

I know for a fact that the stock pump can do this too

Lazy JW":cx5zeezr said:

'68falconohio":cx5zeezr said:

slightly off topic.
What if you sport the elec. pump with the mech. pump and the diaphragm goes out in the mechy? pan full of gas but the carb still gets enough fuel?

Click to expand...

I know for a fact that the stock pump can do this too

Click to expand...

Thanks, Joe. I havn't had it happen to me before but a bud said they do fail. It doesn't starve the carb and alert the operator; that's almost fantastic. :|

A stock fuel pump puts out quite a bit more volume than a stock engine needs even at WOT; a pinhole leak won't starve the engine but it can fill the crankcase in fairly short order. I've seen it happen. First clue: your engine suddenly stops using oil and now is MAKING it
Joe

Ahh, I understand now. I was envisioning the failure to quickly grow from a pinhole to major leak with the number of cycles per minute that the pump makes. Sneaky little guys.
Thanks,
Stephen

If it's flooding, then holding the gas pedal all the way open will help get it going. It needs air, not gas.
Perhaps this is what you are affecting when you say you have to "give it gas" when what you are doing is giving it air.

Jackfish - I think the fuel is boiling in the bowl and evaporating so when he goes to start it, there's not enough fuel in the bowl to get it going. It's also possible that the fuel is expanding as it's about to boil and some of it does go down the carb throat into the motor. Definately more than one way to analyze this.

I've had this problem for years. I've tried timing, float adjusted lower, heat shield, and several different carbs. As built my car did not come with a water cooled base. I've found nothing to fix this problem. I'm wondering if the 5% ethanol fuel and the former MBTE additives in the fuel contribute to the problem.

I'm clueless to what will fix this problem. Mine definately is a flooding problem but not so much as to dilute the oil. Just enough to cause the warm starting issue. I've watched it boil over from the bowl straight out of the venturi. It does it for a very short time, less than a minute. If I let the car sit for a couple of hours I don't have the starting problem. Very high evaporation rate apparently.

One other reason I use a electric fuel pump is when going to cruise night or car show or going anywhere, just before I arrive I can shut the pump off and let the fuel in the bowl get me into the parking lot or wherever. This way the bowl is nearly empty just as I shut the car off. When I go to leave, I turn the key to 'on' position then turn the fuel pump on......wait a few seconds, and fire her up.......