356 B won't start when hot

[Joseph Jablecki]

Drove the car 20 miles to have steering adjusted. Left the shop and ate breakfast. Topped of tank with 93 octane fuel. Drove 6 Miles to planned meeting. 1 hour 15 minutes later car started fine and drove 20 miles toward home. Stopped to get a soda. Outside air temperature 105 degrees. Got into car, started fine, backed it out of parking space, drove it 50 - 75 feet and engine quit. Will not start. After I let it sit a while and try it the engine sputters but quits and will not even sputter again. Until I let it sit a while and then same thing. Engine sputters but quits and will not even sputter again. What is going on????

[Mike Wilson]

Spitballing: Fuel selector rod on Zu; vapor lock...depending on model, blocked gas tank vent; floats stuck...

Mike

[David Jones]

105 degrees is hot and modern fuel vaporizes quickly. Hold your foot to the floor and spin it over till it catches. When you stopped the fuel in the carbs boiled over and all the fumes in the intake manifold made for a super rich mixture and you have to blow them out before the engine will start. Also you don't need 93 octane in a "B" car unless it has been rebuilt with a higher compression. 85 octane would be OK if you could find it.
Failing that it could be vapor lock, a weak fuel pump or a restriction in the fuel line causing the fuel to vaporize over the restriction when hot.
Look down the carbs with the air cleaner removed and see if there is fuel coming out of the accelerator pump jets when you actuate the throttle.

[Joseph Jablecki]

Thanks! After I got it home (Tow) and left it in Garage it started right up. The consensus is: When I turned it off at the last stop, it ran on what was left in the carb bowls for the 50 feet. Then too hot (vapor lock) for fuel pump to refill the bowls. So, if it happens again, I will do the trick of holding the pedal to the floor until it kicks over and save the tow charge. Also, thanks for the advice on the fuel quality. I can get 87 Octane here. Joe

[Richard Shilling]

This really brings home the advances in automobiles over the last 50 years. Vapor lock, overheating, etc. were common "back in the day" but unknown today to where it's easy to forget that our tubs are obsolete and have to be treated as such.

[Mike Wilson]

Wouldn't an electric fuel pump starter kit solve the problem?

Mike

[Martin Benade]

I have heard some disagree with this, but my 356s always have become flooded after a hot soak. Extended cranking with my foot on the floor always makes it start, unless it was 6v and the battery ran down first. Same story with an electric fuel pump, it was flooded just the same. I have never had vapor lock on mine.

[Martin Bruechle]

The old school trick for vapor lock was to put a bunch of wooden clothes pins on the metal fuel line to dissipate the heat.
That would look great on a 356. lmao

[Mike Wilson]

German clothes pins of course! Ha!

Mike

[C J Murray]

Joseph, does your car have the early fuel pump with the filter screen under the lid on top or the late style pump without a filter screen?

After having a couple of vapor lock incidents with early style pumps and never ever having that problem with the later style pumps I do wonder if Porsche changed that part to avoid vapor lock as well as eliminating the set-up complexity of the old pump. The new style pump also does a quicker job of filling empty carbs after the car sits unused for a long period of time.

[John Clarke]

Hi Joseph
Ron Ladow of Precision Matters has designed a fuel/gas purging system to stop this condition.
Look him up, no affiliation.
Cheers Jay

[Ron LaDow]

Hi Joseph
Ron Ladow of Precision Matters has designed a fuel/gas purging system to stop this condition.
Look him up, no affiliation.
Cheers Jay

Jay,
If you mean this:
http://precisionmatters.biz/auto-prime-primer-kit.php
It won't help a flooded or rich condition. It refills float bowls emptied by evaporation between uses, making starting much easier.

[John Clarke]

Sorry Joseph and Ron
I thought that was the problem, modern fuel evaporation, ie fill the float bowls with gas and you're ready to fire up?
Jay

[Tim Berardelli]

To preclude "hot soak" flooding turn the fuel OFF 45 seconds prior to engine shutdown to lower the float levels-this will also help eliminate the "honey your car makes the (pick one) garage, house, universe" stink of gas.

[George Walling]

Joseph, I had the same problem with my speedster here in Oregon with the ethanol modern fuel I'm lucky lots of stations offer non-ethanol fuel so I use nothing but it. What I did was carry a spray bottle of water in the car like we use to do back in the day when vapor lock was a problem. when it happened when the temp was hot usually around 90+ outside and a run of about 10 to 16 miles and I stopped for a short period and the car wouldn't start I would just spray the fuel pump and metal line running up to the zenith carbs. car always started then with very little cranking. The way I knew it was a vapor lock is I have a clear fuel filter inline running up to the carbs and seen the fuel bubbling in the filter I had a bottle of drinking water with me so just poured it down the fuel line and on the fuel pump. might try that trick until you find a better solution, if it fixes the start problem great plus bottle of water is cheap way to trouble shoot the problem. Good luck