"72 Hot (110 degrees) start up

[Jerome P.]

Today it was 110 degrees in the Phoenix area and I took my '72 out for a short run. Initial start up was fine. Stopped at a friends for 30 minutes and the car sat in the direct sun during that time period. Upon restarting the car cranked and cranked before finally turning over. I did pump the throttle once when it did not fire up immediately. After the one pump of the throttle it continued to crank, but ultimately did start.

Have not had this problem in the past, but then again I do not think it was 110 degrees.

Any comments or thoughts as to what may have been going on?

[Edward J.]

Re: "72 Hot (110 degrees) start up

Jerome, I am not sure about the gasoline in AZ. but if you have ethanol this is a typical issue in very hot weather. Long crank and hot re-starts are common.

[Ken R.]

Re: "72 Hot (110 degrees) start up

From our recent experience with a certain 63 on the TX road tour that had a similar happening; his fuel line was installed right next to the lower radiator hose. Thus a lot of heat soak when he stopped or slowed down in traffic. Insulating his fuel line and pulling it away from hose fixed his problem. Heat soak into the carb base and the fuel mixture is summer problem.

[Michael J.]

Re: "72 Hot (110 degrees) start up

On hot starts, I always hold the accelerator pedal 1/2 way down during cranking (as shown in the owners manual, page 7) it usually starts right up after a few turns. But, I am also usually using ethanol free premium too.

[Duke W.]

Re: "72 Hot (110 degrees) start up

The engine was probably "flooded" due to hot soak fuel percolation. This is a common problem with modern E10 fuel in hot weather. Follow the "flooded engine start" procedure in your owner's manual. If there are no security issues where the car is parked, open the hood or pop the hood latch to allow the hot underhood air to escape.

There have been many discussions on this issue including schemes to insulate the fuel lines with before and after temperature readings that showed significant temperature drops.

Duke

[Domenic T.]

Re: "72 Hot (110 degrees) start up

I have a similar problem here in Palm Springs when the temp gets in the 100's and I use our 91 pump gas. I find that it starts faster when I hold the pedal to the floor when it sits for a while after a it was shut down at operating temps. Same as what Michael is describing 1/2 pedal, but I use full pedal, kinda what Duke is saying about flooding, it starts better using the flooding procedure.
DOM

[Don W.]

Re: "72 Hot (110 degrees) start up

Hi Jerry...for my '69 big block, it starts fine cold. If I start it again within several hours, it's either I don't even touch the gas pedal or I hold the pedal to floor to get a 2nd start...Don

[Duke W.]

Re: "72 Hot (110 degrees) start up

The flooded engine procedure in typical owner's manuals says to hold the throttle pedal to the floor and crank the engine until it starts. If you stop cranking after a few seconds, keep the throttle pedal on the floor and crank again. Repeat until the engine starts. Keep the throttle continuously on the floor between cranking events.

Heat soak percolation can cause a very rich mixture in the air horn that is beyond the rich ignitability limit, especially in hot weather. By cranking with the throttle full open there is insufficient manifold and venturi vacuum to pull in more fuel, so the engine is just pumping air, and once the A/F ratio drops below the rich ignitability limit, the engine should start.

If you lift off the throttle between cranking events and then floor it again on the next attempt the accelertor pump adds more fuel which will just exacerbate the flooded condition.

Flooding is almost impossible on modern cars, but it was fairly common back in the days when nearly all engines had carburetors.

Duke

[Jerome P.]

Re: "72 Hot (110 degrees) start up

Thanks for the input Duke.

In your opinion is the problem attributable to "heat soak" from fuel in general and/or does E10 fuel aggravate the problem?

[Dave C.]

Re: "72 Hot (110 degrees) start up

The flooded engine procedure in typical owner's manuals says to hold the throttle pedal to the floor and crank the engine until it starts. If you stop cranking after a few seconds, keep the throttle pedal on the floor and crank again. Repeat until the engine starts. Keep the throttle continuously on the floor between cranking events.

Heat soak percolation can cause a very rich mixture in the air horn that is beyond the rich ignitability limit, especially in hot weather. By cranking with the throttle full open there is insufficient manifold and venturi vacuum to pull in more fuel, so the engine is just pumping air, and once the A/F ratio drops below the rich ignitability limit, the engine should start.

If you lift off the throttle between cranking events and then floor it again on the next attempt the accelertor pump adds more fuel which will just exacerbate the flooded condition.

Flooding is almost impossible on modern cars, but it was fairly common back in the days when nearly all engines had carburetors.

Duke

Thanks for that explanation Duke I have been going through the same problem, car starts on first crank when cold but after that ( usually when a bunch of people are watching ) very excessive cranking with 3/4 throttle and finally starts. this is happening to my 67 tri power, my old 66 450 horse never had this problem , single 4 barrel though.

[Duke W.]

Re: "72 Hot (110 degrees) start up

Thanks for the input Duke.

In your opinion is the problem attributable to "heat soak" from fuel in general and/or does E10 fuel aggravate the problem?

Heat soak percolation is more of a problem with E10 than most straight gasoline blends because E10 has a lower by up to 20 degrees 40-60 percent boiling range.

Gasoline is a blend of hundreds of different hydrocarbon species. The "distillation curve" is the percent of species that are at and above their boiling points. Ethanol boils at 170F, and it is the culprit in lowering the mid range distillation curve in modern gasolines. Modern engines are not affected because all have pressurized fuel systems.

Duke

[Jerome P.]

Re: "72 Hot (110 degrees) start up

Duke and others,

Thanks for all the good info and your thoughts.