Hard to Start When Hot.....Carb?

[grasmo]

if alcohol was the problem in this case the car would be harder to start when cold, not hot.

 

[Gary S]

if alcohol was the problem in this case the car would be harder to start when cold, not hot.

Not necessarily. Ethanol does have serious problems igniting at low temperatures and causing cold start problems, but those problems show up at very low temperatures like -20F.
Ethanol also has a much lower boiling point than gasoline which causes vapor lock problems. Ethanol boils at 173 degrees F which is easily reachable on a hot engine that is sitting for a while. Pure gasoline's boiling point is around 425 degrees F. It can be made to boil much lower than that using additives, but good automotive gasoline won't have additives that make is useless as motor fuel.

 

[ZHUGGER]

Usually I take the car for a spin and come home and park it for the day. Recently I have been driving the car on weekends for whatever is going on.

I've noticed that if I turn the car off after it is up to normal operating temperature (180*) and let it sit for a while.....I have to hold the gas pedal to the floor and crank the engine for about 4 seconds before it will fire up.....Then of course, when it fires the exhaust smells like gas until it burns off.

Carb or timing?

I have a 1000A battery, a CS130 alt, and a MSD6AL so I know I have plenty of spark. Carb is the Holley SA 770. Mechanical fuel pump.

FWIW, sometimes I notice that when the car is cold and has sat for a few days/weeks, the fuel filter is empty but several people have said that is normal.

Exactly what mine does, still havent figured it out. I'm going to find some fuel without the ethanol!!!

 

[Jrod79Z]

Real Gasoline where are you?

Thanks for all the input folks! I think I heard fuel actually boiling after my Z had sat for a few minutes after driving home one day. I need to move my fuel line away from the intake too (Aluminum with Edelbrock 650) and might try insulating the fuel line up there too. Real gasoline. Who would of thought we could not get it.

Jeremy

 

[tacotoy]

ive seen this happen alot with mechanical pumps, the heat soaks thru the pump after it sits for a while and boils the fuel since its not sitting under pressure.

people have fixed it more often than not with the addition of a small electric fuel pump in line back towards the tank. alot harder for the unpressurized fuel to vapor lock if the line is pressurized thru the whole engine compartment.

 

[MrAzzhat2U]

Many things can and will contribute to this problem!If your car has headers and it's a heat soak problem,try this,when you park the car,open the hood to let the heat out.If it solves or reduces the problem there isn't a lot you can do short of installing an after blow fan setup to cool it off.

As others have said,todays fuel contains a lot more ethenol than years ago and it will boil at a lower temp,a cool can will fix it.Also,someone mentioned lowering the float level,that can help,but might cause a WOT problem,this could be a trial and error method.

I have seen a lot of this lately and think it's more of the fuel quality than anything else!This is just my opinion!