Thread: Engine Start

Tweet

If the O.P. is using the stock engine driven pump, it indeed would have check valves.

not necessarily, the diaphragm may have a hole/tear in it.

Godspeed
MrC.

then the gas above the diaphragm would drool into the motor. but the line above (going to the carb) would remain full. The inlet side check valve would prevent drainback.

no update yet proly be this weekend before I get a chance to look at again. Lot of overtime right now

One more thing I have a electric fuel pump in the tank.

JMHO;
The float bowl is vented and needle valve (fuel inlet) is above float level and will not allow the fuel to siphon from the float bowls. The fuel line could siphon back, but there should still be enough fuel in the bowls to start and run until the fuel line is re-charged. If the float bowls are empty it is either heat soak or a cracked float bowl.

If it is heat soak, the car will also start hard when it is cold as there will be no fuel in the bowl to prime the accelerator pump charge that's needed for the cold start until it cranks enough to fill the bowls. If the float bowl is cracked or damaged fuel will leak all the time, again hard to start when cold and most likely fuel on the motor.

Unlike EFI, carburetors are not self priming. If you're not giving it a little gas at a warm start, you will have to crank it until the venturies pass enough gas to prime the motor.

Again, JMHO, but sometimes we overlook the simple.

What fuel pump?
If its carbed you need to set pressure to 5 - 6 lbs & use a return style regulator

Originally Posted by t-top havoc

What fuel pump?
If its carbed you need to set pressure to 5 - 6 lbs & use a return style regulator

He can also use a deadhead regulator and set to the 5 pounds. Then he won't need a return line.
But until he verifys that he's lost fuel after sitting there hot, it's all a guess.

.
Erased post.

are you people making this up as you go along? What float bowl check valve (needle and seat) is so low it would empty the bowl? and what diaphragm leaks in the motor instead of on the motor? which would be easy to spot from the flames.

What is his timing set at? where is the coil mounted and most important if you wait til it cools down a little more does it start?

Actually, I've seen fuel pump diaphragm failure result in fuel in the crankcase. Oil pressure really gets bad. And no, the motor didn't blow up. More often, the fuel will vent out the weep hole; that's what it's there for. Of course I'm talking about mechanical pumps mounted on the side of the motor.

Originally Posted by MalibuChevelle

and what diaphragm leaks in the motor instead of on the motor? which would be easy to spot from the flames.

What is his timing set at? where is the coil mounted and most important if you wait til it cools down a little more does it start?

Way more common that fuel goes into the motor in my experience. So common that whenever we checked oil in the service stations I worked for, we automatically sniffed the oil on the stick. Probably saved dozens of folks their engines.

As for the rest of the questions.. we're all standing by waiting to ask the O.P. once he has time to investigate and come back with findings. Sometimes it's a slow process as daily life still happens...

Update, I done a couple checks opened up the gas cap as someone asked while it was running shut it off bout 20mins made no differance. I also took the breather off to see if there were any vapor coming up didn't see anything or any gas dripping down. I do have a regulator that is set between 5 an 6 also with a return line to the tank. I'll keep looking.

I read it as an accelerator pump diaphragm which leak to the outside of the carburetor on to the engine and could result in fire. Either way there should be an obvious gas smell.

sure on AFB style or Quadrajets can leak from plugs into the engine, but they don't have diaphragms they have plungers that can only leak back into the bowls . Do we even know what kind of carb 39 chevy has?