Fuel System: Do I need a pressure regulator?

[BShaw]

Tried starting the hawk tonight for the first time. Turned over well and oil pressure jumped right up there. Pretty sure we stabbed the Unilite in correctly. However, it won't fire and it sure seems like it is getting a LOT of fuel. I am using the electric fuel pump sold by S.I. and many other Stude vendors (don't recall which one I bought this from). I was under the impression that this pump puts out the 5 psi or so that I should have. Is this correct or should I be using a pressure regulator to ensure what pressure is being delivered to the carb?

When cranking it over, fuel is literally bubbling out of the top of the carb (edel 1403) in a couple of spots.

Any thoughts appreciated.

[jclary]

Bob, is this the only fuel pump or are you using it as a supplemental back up as many do? Could be that your float adjustment is not right in the carb. Do you have a manual switch where you can switch the pump off? (Mainly thinking out loud here?)

[BShaw]

Only have the electric pump. The carb/intake came straight from my old motor where it started/ran well (fuel-wise) albiet on the original mechanical fuel pump.

To clarify, the fuel I'm seeing is coming up under/around where the step-up pistons are located.

[jclary]

I was just wondering if you were pumping so much gas that you were overwhelming (flooding) the engine causing the spark current to simply dead short in the engine...thus, no spark to ignite the fuel. One way to test whether or not the engine will fire would be to shut off the fuel pump and simply pour in a small amount of gas to prime the carburetor and see if it fires up.

Today, I had to prime a carburetor on a small tractor just to get it going while freeing up a stuck needle valve.

[JoeHall]

I doubt very seriously that it is due to excess pump pressure. Sounds like sticking float/fuel inlet valve. Tap on the side of the carb with a screwdriver handle, around the area where the fuel line plugs into it. Sometimes that will free it up, at least for a little while. Might need to pop the top of the carb off and clean & polish the inlet valve, bore & seat. I use a piece of green scrub pad.

You do not need a PR with that pump.

[jclary]

OK, so according to Joe's theory, you may not be getting fuel through the carburetor. If it is due to a stuck inlet valve...let's hope it is not one of those with the rubber tip that has fallen prey to the ethanol curse. I have had those to crumble when freed up.

[PlainBrownR2]

Hopefully not with the needle valves. You'll know it's the needle valves from a couple different ways. If you can take the rubber off of the steel line going into the carburetor, and either blow through it or blow through it with the air compressor, and it feel restricted, it might be a stuck needle valve. If you can also prime it by putting gas in the vents that go into the bowls, and it will run for only a minute before dying(needle valve is stuck and preventing fuel from coming into the bowls and they run dry), that's also a way to tell that they are stuck. In this case, it seems fuel is getting into the bowls, so it doesn't sound like they are stuck. Just for haha's sake, and with the spark plug out, rotate the engine around so the #1 piston is at TDC, and that the mark on the damper is aligned with the pointer. Drop the Mallory back in with the vacuum advanced pointed at the passenger side, and get the rotor to align with the #1 spark plug terminal under the cap, give that a whirl. I know, this is all academic, but it sounds like it's not doing it's hiccup, so seems like it's getting fuel(a whole lotta fuel!), but it's not getting any spark, or the advance needs to be adjusted.

[Milaca]

I would also guess that the float needle/valve is not closing the inlet port (where the fuel line enters the carburetor), thus allowing fuel to enter the carburetor uncontrollably. It could be due to varnished gas in the carburetor or a speck of dirt between the needle and seat.

[BShaw]

It appears Mr. Clary hit the nail on the head in post #4. My wife called me in for a sandwich and upon my return to the garage, the ol gal fired right up! Woo Hoo! I still have some issues to sort out but IT LIVES!!!!!

Back To The Fifties Weekend starts tomorrow so I will be going to the MN State Fairgrounds with out of town friends Fri, Sat and Sunday. But, Monday a.m., back to work on the Hawk (with renewed vigor)!

[JoeHall]

Based on the PO's description of symptoms, "literally bubbling out of the top of the carb", I was thinking the inlet valve may be stuck OPEN (not closed), thus allowing gas to flood high enough in the float bowl to seep out around the top of the carb.
I recently cleaned up the inlet valve on an old AFB, that's been on the 56J forever. There was nothing wrong with the rubber point of the valve. I cleaned it as described above, with a green scrub pad. Unless the carb is near new, it wouldn't hurt to pop the top off and clean the valve anyway, though they seldom really need it.

[rodnutrandy]

Edelbrock claims you want no more than 6 lbs. pressure to carb. a stock mechanical fuel pump on my 350 was pushing 10 lbs. . I installed a regulator and am more at ease. You might check pressure of your electric pump.

[ROADRACELARK]

Just to be on the safe side, you might pull the dip stick to check the oil level, but more so to take a whiff to see if any of that gas over flow found its way to the oil pan. It wouldn't take a whole lot of gas mixed with the engine oil to do some major damage to the bearings! ! ! ! Just a safety thought. Hope this helps.

Dan Miller
Auburn, GA