fuel

[bobsmanstuff]

Hey Guys, About a month ago we took a ride on a warm day to fill the tank. It's been in the garage since. I went out today and it won't start. I pour gas down the carb and it runs until thats used up. Could there be a vapor lock? It's not getting gas. Thanks Bob

[ford38v8]

Not vapor lock. Pump gasket, diaphram, or check valves, or blockage in the line. Remove flex line from pump, blow air to tank to hear bubbles. Replace flex line, remove line from carb, and with ignition OFF, direct line to a container to check function of the pump.

[51 MERC-CT]

This is a common problem after a long time not being used due to evaporation and drain-back.
Do not remove any fuel lines until you have confirmed that the choke is operating.

If after considerable cranking and with no signs of fuel to the carb., then further exploration can be done.

[drolston]

If it will run for a few seconds on prime in the carb, that should be enough for the fuel pump to get fuel up from the tank. After doing that and still no start, disconnect the fuel line at the carb and crank with ignition OFF to see if the fuel line spurts fuel. If no spurting fuel, crank for a few more seconds; still no fuel flow - time to check out and maybe rebuild the fuel pump.

If you get decent spurts (about a tablespoon on each cycle) then you probably have a carb float valve stuck closed. Not uncommon for an engine that has set for months. The fuel in the carb evaporates leaving a little residue which might be sticky, particularly if you add MMO or anything else to your gas.

To unstick the float valve: First, while the fuel line is disconnected, squirt a blast of carb cleaner into the fitting on the carb. Then tap sharply several times on the fuel fitting on the carb with the handle of a screwdriver or a plastic face mallet. Do not tap on the carb top itself, only the brass fitting. Try blowing through the fuel fitting using a length of hose. It won't flow much, but you should be able to sense a little air flow.

Then try to start it again. Should fire up after a few seconds of cranking to fill the float bowl. If not, time for the top of the carb to come off. If the float bowl is near empty, remove the float valve and clean or replace. If the float bowl is near full, then you have a carburetor problem.

Footnote: I know a few flatheads that simply will not start unless you apply a lot of choke. Be sure you have a working choke.

[bobsmanstuff]

Thanks guys. If that doesn't do the trick I do have another pump.

[bobsmanstuff]

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One more question, if I change out the fuel pump should I put anything on the gasket or just put it on dry? Thanks

[51 MERC-CT]

Originally Posted by bobsmanstuff

One more question, if I change out the fuel pump should I put anything on the gasket or just put it on dry? Thanks

Dry!

[bobsmanstuff]

Thank you Sir.

[Desoto291Hemi]

Now I guess I am wrong,,,,,,but if he pours gas down the carb,,,,,,and it runs until that is used up,,,,,,then how could the choke possibly be the issue ?
I’m not good on these carbs,,,,,,but the choke shouldn’t keep it from getting fuel,,,,right ?

Tommy

[34PKUP]

Originally Posted by Desoto291Hemi

Now I guess I am wrong,,,,,,but if he pours gas down the carb,,,,,,and it runs until that is used up,,,,,,then how could the choke possibly be the issue ?
I’m not good on these carbs,,,,,,but the choke shouldn’t keep it from getting fuel,,,,right ?

Tommy

Pouring gas down the carb. does not put gas into the carb fuel system, it goes into the intake manifold.
Try starting a cold engine with the choke wide open that does not give a vacuum assist to draw fuel from the carb. fuel system.

[bobsmanstuff]

My choke is working fine.

[51 MERC-CT]

Originally Posted by bobsmanstuff

My choke is working fine.

Perhaps a pump replacement is in order.
As part of that process I would check the pump push rod for movement
( appox. .200" )

If you are running a double-pumper fuel pump, there have been, over the years, reports of the fuel pump lobe on the cam being worn down partly due to the excess pressure on the cam lobe.
( I got rid of my double-pumper years ago. )

[drolston]

Originally Posted by Desoto291Hemi

Now I guess I am wrong,,,,,,but if he pours gas down the carb,,,,,,and it runs until that is used up,,,,,,then how could the choke possibly be the issue ?
I’m not good on these carbs,,,,,,but the choke shouldn’t keep it from getting fuel,,,,right ?

Tommy

Choke will not keep carb from getting fuel, but even with fuel in the carb, some flatheads will not start without some choke, especially when the engine is cold.

[bobsmanstuff]

Got it going Guy's. It all came down to the carburetor. Some new gaskets and fill the bowl and it popped right off. Thanks for the help. Bob

[Tinker]

Adding choke will increase the amount of fuel by decreasing air input and diverting engine vacuum. I run a little lean on my 38 till it warms up and atomizes fuel. Run the choke shortly (1/4 out) till it warms up. Once it's warm I lay off the choke. Also a good way to know if your carb is running lean if it preforms better with some choke.


If it hasn't been run for a while bottle feeding it till the pump picks up is normal. If needed. If you have to do it every time you want to drive it, it's probably a bad check valve in the pump.

I don't know if anyone remembers when you had a car that you had a starting procedure. two pumps on the accelerator, 1/2 choke, and then tapping the dash twice, made it start every time! haha

[rotorwrench]

A person can prime a dry carburetor if they have a squirt container of fuel. Find the fuel bowl vent and squirt some fuel in there. Sometimes it takes a bit for the fuel pump to break its cavitation and start pumping properly. With a float bowl full of fuel, it can start and run a bit using the throttle carefully to prevent back fire as the fuel charge runs out. The fuel introduced in there might help free up a stuck float valve too.

Running the engine every 14 days helps to prevent stuff like this.