Carburetor Boils Fuel and Hard Restart

[Doug]

When I park my jeep when hot and try to restart ten minutes later, it is hard to start.   When I say hard to start, I mean I will have to keep massaging the gas pedal for 2 minutes until it settles down to keep if from stalling. �I assumed this was due to the fuel boiling in the lines. �Today, I also notice when I had the hood up that I could hear the carburetor pressurized by the boiling of fuel and slightly overflowing when parked hot and engine off.

Is there a setting or adjustment that may be off in my carb that causes this?

[Carls_jeep]

What is the temperature of the thermostat your using and what pressure radiator cap? You should be using a 160-170 deg F thermostat and a 7 psi radiator cap.

You may have to much fuel pressure also.

If the fuel boiled in the lines that is called vapor lock and it likely would not start at all. I suspect what is happening is the fuel pressure is to high causing the fuel to leak past the needle and seat at the float flooding the engine. Running a high temp thermostat and high pressure rad. cap adds to the problem.

EDIT: you could also have a bad needle and seat.

[rocketeer]

Some questions:

Carter or Solex carb?

Stock or electric fuel pump?

If stock fuel pump, with or without vacuum?

Is your heat riser stuck or free?

How close to the exhaust are your fuel lines?

Larry

[Doug]

Carter WO, mechanical fuel pump, 2-3/4 PSI fuel pressure, without vacuum. � �Heat riser functions. � Fuel lines not particularly close to heat riser. �However, I do you an oversize fuel line from pump to carb ( 3/8" in lieu of 1/4" so that it fits a ford fuel filter at the carb). � I am running a 180 degree thermostat. �Jeep operating temperature is 185 degrees with the higher thermostat. �However, it did this before when I ran a 160 degree tstat.

Issue only occurs when the jeep has been run and then parked and then try to start up ten minutes later while still hot. �Then it wants to stall unless I pump the gas pedal for a minute or two. �

I am guessing that the slightly larger fuel line plus the fuel filter (metal) hold more fuel than stock.   Then it probably expands when heated up and overwhelms the float valve.  That would then flood the carb.  What I can't understand is why does it take one minute of running to straighten out.

[Carls_jeep]

If you just hold the throttle open instead of pumping it does it die? I mean, hold it wide open when you try to start it and as the engine picks up rpm's then let off the throttle easy until it smooths out. Or, does it refuse to start if it is held wide open?

It very well could be a defective needle and seat.

[rocketeer]

I think Carl and I are confused by the same thing. If it's boiling over then the issue would be flooding which would make for hard starting. The answer would be to simply hold the pedal all the way to the floor until it starts AND until the flooding is cleared. Don't pump, but don't let it over rev once it starts either.

I'm wondering too about your fuel pressure. Stock, it should be about 4.5lbs at 1800rpm.

As for the flooding, the size of the fuel line and the filter should have no effect. Here are some things to look at:

As mentioned, needle and seat. If the needle is an older one with a neoprene type tip it's possible ethanol has damaged it.
Float set too high. Self-explanatory
Fuel lines too close to exhaust. The line from the pump OUT should go straight towards the fender, then make a turn upwards towards the carb inlet.
Leak in the float. Sometimes the floats develop pinholes (if metal) or get saturated (if composite).
Missing or incorrect insulator gasket between carb and manifold. (Fuel diffuser and gasket).



Larry

[Carls_jeep]

After my last post I got to wondering about that thick gasket and if it got replaced some time along the way with a thin gasket.

How long has it been doing this and what changes have you made before it started doing it.

[Doug]

I have the thick gasket. �Not sure if it has the v or not but it is definitinely the extra thick gasket. �This is my fuel line setup  

[rocketeer]

Lines look good. Just out of curiosity, do you have the spacer between the fuel pump and the block?

Did this just start? Did you change gasoline brands (sounds stupid, I know) by any chance?

Aside from that, it sounds like the prob is in the carb. Take the top off and inspect the needle and seat. Check the float, see if it has fuel inside. Check the float setting making sure the gasket is moved aside when setting it.

Larry

[Doug]

I do not have a spacer under fuel pump.   I may have recited the fuel pressure incorrectly.  I remember when I checked it a year ago it was within spec.   The issue is not new, it has always done it, I just wondered if there was a cure so I would not have to keep tolerating it.  i did not change gas brands.     I will check the carb settings.   You say when measuring float level, do not include the gasket thickness in the measurement.

[rocketeer]

Those Mexican replacement pumps are usually OK so I think we're back to the carb. Yes, set the float without the gasket.





Larry

[Doug]

Thanks

[Carls_jeep]

I got to wondering about the needle and seat problem with the 10% and 15% Ethanol gas so I called Walck's. I told him I had one of the expensive original Carter kits I bought from them and asked if the Ethanol was an issue with the old rubber needle. He said of all the kits they have sold over the years none have given trouble. I had to agree because my carb may have never been rebuilt and it is doing ok so far too.

[rocketeer]

Not all needles have rubber/neoprene tips. Most are just metal. My current carb has an all metal needle as do each of the spares I have.

Larry

[Carls_jeep]

I would prefer the all metal but I have what I have.