Gas going wrong way

When trying to start this engine it runs but raw gas is pushed out the top of the carb and some vacuum plugs are pushed off. Never had this issue in over 60 years of working on old cars. What do you guys think? Thanks

 

Floats stuck open, or way too much fuel pressure.

 

Way too much fuel pressure. What car/engine/carb/fuel pump/fuel pressure regulator are you dealing with?

 

needle valve stuck open/floats sunk and vacuum plugs pushed off by backfiring through carburetor.

time for carb rebuild

 

If the engine has been setting idle and not run for a long period of time, you may have a couple of intake valves that are sticking and not closing fully. This can allow combustion pressure to back-feed into the intake manifold. Pressurizing the intake can push vacuum hoses an caps off their fittings. Can also damage the power valves if the carburetor is so equipped. Doing a compression test can also help narrow down problem areas.

A bit more info like engine make and style, carburetor, etc. would be helpful also.

 

The engine is a 74 Ford 300 inline 6 with a one barrel carb.. Both carb and fuel pump are new aftermarket stock replacements. Going to do a compression check to check intake valves. Thanks again.

 

I had a friend that owned a '67 Camaro, he put a new Eddy carb on it, installed the gas line to the PCV fitting, the fuel fitting to air cleaner. Called me up and said it won't. Went over to garage and told him he was lucky it wouldn't start, oil pan was half full of gas!

 

“New” Aftermarket carburetors are usually Chinese copy’s of the original and problematic, rebuilt OEM carburetors are the way to go.

 

Compression checked out good 130 -145 so valves, rings etc good. So what else causes vacuum plugs to blow off? Thanks!

 

timing way early,
plug wires out of order or cross firing

 

The worst mistake is to assume that a new part is automatically good, you have to check to verify that it is good or discover that it is faulty! That's why they have warranty on new parts, because there is a percentage of new parts that are faulty.

 

^
And that percentage of defective new parts is a lot higher now, then it was 5 years ago.
A part being new no longer means the part is good.
These days, with some new parts, it may take 2-3 tries at a new part, before you get a good one!

 

Fuel coming out the vent is covered. The needle and seat are not shutting off flow, either won't fully seat or too much pressure.
When the carb doesn't shut off fuel supply, the fuel pours down the intake into the engine. Take care to not hydraulic lock the engine and check the oil for contamination.

Well, that's interesting.
What causes things to blow off is pressure. Normally they have atmospheric pressure on both sides (engine off) or a lower pressure in the port (engine on). You've got higher pressure in the port, so it pops the caps off.
Fix or replace the carb, then crank the engine over without ignition. If it pops off, valve timing or a stuck intake is the cause. If not, recheck the ignition timing and introduce spark. If it pops off, recheck ignition.