no fuel in the carburetor after a day

[madrat]

hey guys.

i have a second hand datsun 720p king cab and after a few days off not being used there is no fuel in the carburetor, can someone please tell me if/how to fix this

thanks

[datzenmike]

How do you know it's empty? Did you remove the front cover with the round glass for checking the fuel level?

 

Chances are it's leaking around the outer seal, possibly the float is set too low also. You might notice a gas smell if it was. There are not many ways for the gas to get out, no gaskets seal it in but the front cover.

[banzai510(hainz)]

unless yu have a sight glass its hard to tell.

 

one way is to cycle the linkage and see if gas squirts in the carb via the accell pump if yes it squirts then the bowl has gas.  Be honest after a few days mine(weber 32/36 is hard to start also till the pump get gas in the bowl

[madrat]

ive had a mechanic tell me it is going back to the tank

[Lockleaf]

I had a Nissan dealer mechanic tell me my timing had skipped a tooth. Turns out my cam shaft was busted in half and only running 2 cylinders.

 

Point being, they can be wrong, so find out how he concluded that fuel loss at carb is your problem.

[datzenmike]

Absolutely impossible for it to run back into the tank. Everything in the line filter and fuel pump ... might siphon back.

[datsunaholic]

It fills from the top.  Can't siphon back out, since there's an air gap.  Can leak through the jets, or evaporate (Hitachis are pretty sealed so it takes time, but my Webers evaporate in a day since they're open to the atmosphere at the top).

 

Now, the lines themselves, if there's a small air leak they can easily drain back to the tank.

[madrat]

It fills from the top.  Can't siphon back out, since there's an air gap.  Can leak through the jets, or evaporate (Hitachis are pretty sealed so it takes time, but my Webers evaporate in a day since they're open to the atmosphere at the top).

 

Now, the lines themselves, if there's a small air leak they can easily drain back to the tank.

so there could be an air leak in my fuel line, would that also explain why it'll back fire whilst driving?

[datzenmike]

The fuel pump may suck in air from a loose hose clamp. This would only mean less fuel going to the carb fuel bowl. The carb draws it's fuel supply from the fuel bowl not the pump. The fuel pump merely tries to keep the fuel bowl full. If it ran dry the engine quits like running out of gas.

 

Backfire out exhaust or the air filter?????

 

Check your fuel level by looking at the glass window on front of carb. Fuel should be at the line or dot on the glass if you have the round window.

[weldingrod]

Return line has a check valve; if that fails then could siphon back to tank. Valve mounted on top of fuel tank. Dealer told me 6 weeks because nobody has ever ordered one and it has to come from Japan, by slow boat I assume. Pull check valve and if you can blow through it both ways probably toasted. Don't know why any gasoline fuel check valve wouldn't work, just OEM filter fits bracket on fuel tank. Thinking zap strap.

[datzenmike]

Theoretically gas could siphon back from as far forward as the inlet of the carb, but not possible to empty the fuel bowl.

 

The check valve on the tank should be on the vent pipe that goes to the charcoal canister. As the fuel line and return lines are sealed to the carburetor only the vent line needs a check valve to prevent gas getting out of the tank in a roll over