12V on/off switch for fuel pump cut off?

[lars1965]

anyone who have made this:12V on/off switch for fuel pump cut off? so you can cut off the fuelpump when engine is running, just before parking to prevent fuel boiling... when you park shortly.

Thanks

rg.Lars

[edmayo]

Even here in Texas have never had to do that, even when shutting off engine between autocross runs on a 100 degree day. Are you running carb insulators between manifold and head? Unless your gasoline is worse than ours!!

[lars1965]

Yes , I run with 4mm phenolic spacers between heads and manifold and 3 mm between manifold and carbs , so total 7mm and both with gaskets on both sides. It have improved but not enough, i`m starting to go crasy, when I start between 5 min- 11/2 hour after last drive in hot weather, I let the starter crank about 5 sec without touching the gaspedal and then slowly depresseing gaspedal about 1/3 , and when it start I hold rpm on 2000-2500 in 10-15 sec to let the rich mixture out of the tailpipe...

but sometime I forget , and the engine dies, sometimes it feels like a air or steam pocket in the weber 40 ida carbs( the are in very nice conition, and run with partsklassik cdi) sparkplugs look great.

Anyone who have done the upgrade for the boiling issue that performanceoriented offer?

I would really like to get this problem done for good, as I use the car a lot in Europa during summer.

[edmayo]

Have you ever removed the air cleaner to see if you observe fuel dripping onto the throttle plates after a hot shut off?

[ibmiked]

Lars, I have installed a fuel pump cut off switch which I use when having hot start issues. I too have the phenolic spacers along with a hot-start relay, and a high torque starter yet still experience difficulty sometimes. This may have no basis in reality, but I shut off the fuel pump and then crank the motor a few times before engaging the pump again. It seems to clear the cylinders and perhaps has the added benefit of drawing cooler air into them before reintroducing fuel.

Anyway, it seems to work for me when things get stubborn.

[lars1965]

Hi ed, no but I will check...

Hi ibmiked, thanks can you show how you have wired the cut of switch to the pump...? and do you also shutt the pump of just before parking?

rg.Lars

[edmayo]

I'm curious, Mike, Lars, do both of you as a matter of procedure open the throttles when starting, hot or cold.

[lars1965]

COLD: turn the key 1 stage , pump runs, slowly press the gas pedal to the floor 3 times. tun the key to start, let the strter run, slowly press gaspedal 1/3

HOT: turn key 1 stage, pump runs , turn key to start, I let the starter crank about 5 sec without touching the gaspedal and then slowly depresseing gaspedal about 1/3 , and when it start I hold rpm on 2000-2500 in 10-15 sec to let the rich mixture out of the tailpipe...

[ibmiked]

COLD: turn the key 1 stage , pump runs, slowly press the gas pedal to the floor 3 times. tun the key to start, let the strter run, slowly press gaspedal 1/3

HOT: turn key 1 stage, pump runs , turn key to start, I let the starter crank about 5 sec without touching the gaspedal and then slowly depresseing gaspedal about 1/3 , and when it start I hold rpm on 2000-2500 in 10-15 sec to let the rich mixture out of the tailpipe...

Ed,

Cold: 2 pumps then hold to the floor when cranking

Hot: hold to the floor without pumping

[lars1965]

Hi ibmiked
What car do you drive, carbs, mfi , year, just so we compare the same troubles...