Engine seized from excessive fuel. Why?

Running a Holley 750 Street HP and 110 gph electric fuel pump.

I had cut away most of the fuel lines and was replacing with new hard lines and new braided stainless. Before I started it up, I wanted to check for leaks, so I turned the key to ON, fuel pump pressurized the system, and I spent maybe two minutes checking the lines and connections for any leaks.

I have never let the pump run this long before starting the car.

Anyway, no leaks, fuel pressure steady at 6 psi, tried to start the car. Two pumps on the pedal and didn't immediately start. Turned the engine over a few more seconds and it stopped. It wasn't a hard stop, as if the engine had oil starved and seized, or like something solid was dropped in through the intake.

So I pulled all the spark plugs and turned it over again, and tons of gas shot out everywhere.

Plugs back in, started up almost like normal after a little bit of turning over.

Why did this gas dump into the intake?

Do I have some valve or other broken or malfunctioning in my carb?

Floats were ok last time I checked, but that was well over a year ago.

Anything else I should check out?

 

6 Psi shouldn't be enough to push the needle off the seat. It is usually caused by a stuck float or high float setting.
Turn the pump on and look into the carb to see where gas is running in. A stuck float will usually cause fuel to come through the vent tubes.

 

Btw you should change the oil as soon as you figure out the problem.

 

With all of the new fuel line installed you more than likely have metal particles stuck in the needle and seat. I'd unscrew the needles and check before I ran it again.

 

Due for an oil change soon anyway.

I will check all of the above. Hoping it is just a float set too high or something simple.

 

And run a compression check just to be sure you didn't damage any internals with that "hydraulic" stop...

 

X2!
I have had the same thing happen. All it takes is a little piece of old hose, rust, or grit to get stuck in the needle valve and cause flooding. I would (in addition to what "Maverocket" said, remove your fuel line at the carb and let the fuel pump run fuel into a container for several seconds. This high volume flow will help to flush any crap out that's in the system.

 

I believe my Holley black pump is pre-set at 8psi

 

A non-metallic container -FOR SURE...

 

Pull the carb apart. Im betting you have debris in the needle and seat. Clean it up and reassemble. Replace fuel filter depending on location and flush the lines. I got a tiny piece of fuel hose stuck in my secondary needle after doing my line change. Not a big job but annoying.

 

Everything mentioned above is exactly right. This is a common problem after working on fuel lines. Flush the lines like simple man and Darren already mentioned. Don't be surprised if it happens again.

 

why do you pump the pedal with an electric fuel pump? the gas dumped into the intake because the pump was pumping it had to go somewhere

 

No choke. So I prime the engine with two pumps of accelerator pump. Otherwise, won't start. Especially when the weather is cold.

 

Pretty common, done that a few times myself and it can be a real pain. Your lucky it didn't fire that would have been bad. Remember to look down the carb first and be thankful you had a smaller fuel pump because it don't take long to fill a motor up.

 

So, to prevent this in the future, just don't let the fuel pump run without the engine running?