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Gas Leak From Carb Float


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Hello Everyone!


I have a hitachi carb. In the past I had start up problems that were corrected by pouring gas into the carb. Unfortunately my '76 620 refuses to start. I have removed the air filter and poured gas directly into the bowl, resulting in a the truck running for 15-20 seconds and then the engine died. The truck has sat for a month so I don't believe it's flooded. Today, I poured a small amount of gas directly into the carb resulting in the gas leaking from the throat of the carb. Prior to the leak there was no gas in the chamber window. 


Should I remove the whole carb & utilize a rebuild kit? Should I douse it with Carb Cleaner? Could it possibly be a bad float, I tried the banging on the side of the engine strategy with no success. 


Pics of Carb if it helps: https://imgur.com/a/ugihFzn


Plz bless me with your guidance so I may impress my woman & cruise around again,




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Bad float?


Well if the float is brass it could fill with gas and not 'float' causing the carb top over fill and flood. Most floats now are phenolic plastic and can't sink.


If no gas in the float chamber possibly the float is stuck in the closed position or there is a blockage.


The carburetor should be able to hold gas in it for several months. Certainly for a week in hot weather. Even so a few turns of the engine with the starter should refill it.



Get a funnel and direct the gas into one of those diagonally cut vent pipes and you can fill the float chamber. The engine will start and run much longer doing this.

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Alrighty! So I funneled some gas into the float chamber, it seemed to raise up. I slapped all the parts back on & got this result: 



Right after I got out the truck Mission Success Mode Activated, it died 😞  I reintroduced gas into the float chamber & then got this result: 


A super weird heavy turn, kind of a groan from the engine. 


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 Well seems like one cylinder is close to hydro locked. So just take out the #4 (rear) plug and spin with the starter. By hand may not be fast enough. If nothing, take the #3 plug out and work forward. I expect if there is gas in a cylinder it will spray out the #4. Have a handful of rags to catch it but remember this is a very flammable spray. Get the plug wires away from that side. Geez be careful

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  • 2 weeks later...

Hey guys, finally got some time to work on the truck. Turns out the groaning noise in previous videos was due to bad terminal connection from the battery. I cleaned up the battery terminals & have solid electric connection now. 


The carb is still not getting gas from the fuel lines. Perhaps my fuel pump went bad...so I replaced it. I blew air from the carb's gas intake line & had someone verify they could hear air/bubbles from the tank & sure enough they could. There was so air leakage from the fuel filter but it has since been tightened down. 


So new pump, about 5 gallons of fuel in the tank, tight fuel lines, & still a crank with no start.


Here's what it sounded/looked like today after I attempted to start with some starter fluid. 



Side note: how many cranks does it take from the engine to move fuel with a mechanical pump? I read somewhere online that you should try for 30 seconds but that sounds like bad advice lol


Thanks for all the response so far

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Look at the sight glass on the front of the carb. If the fuel level is at the dot then the pump is delivering and the float is set properly. If there is gas in the carburetor it should start.


If level is not showing I guess the easiest thing to do is check the pump. Pull the plug wire off so no chance the engine will start. Connect a hose to the pump outlet and direct it into a suitable container. Have someone turn the engine over with the starter. Gas should shoot out in strong gushes.


If it does, perhaps the float is set too high not letting fuel in or the needle valve above the float is stuck closed or the brass screen is plugged.



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Then pump is having a hard time sucking gas up from the tank.



Take the needle valve out and fill the float chamber with gas. This will get the engine started and revved up. This will work the pump much faster than turning the engine with the starter. This should suck gas up to the pump and prime the system.

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Tightened everything down. The needle valve body was a wee-bit loose. Poured about 2 oz of fuel into the float chamber with some spill over into the carb bowl. She ran for about 8-10 seconds then died. I then checked the Fuel filter & there was a small portion of gas in the filter, YAY! 


I repeated the process once more, amount in fuel filter stayed the same. There was an atrocious grinding noise this time around.. similar to grinding gears.



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to me its a weak battery cables/starter????.  my oct 6th post


Yes this has happen twice to me also. over tighten then the battery cable end will crack and make look like the starter is bad


if the output of the fuel pump there is not gas shooting out then its OBVIOUS. whats wrong.


just going by the vid its hard to tell. Its shounded like it wanted to start so you must have had poured soem gas in the carb to get it to run for a secound or so. But If the vid was shorted I say the truck runs on start then shuts off when the key snaped back to the ON position. this would be also a Ballast resisitor open. as the bypass wire on statrt get the 12volts to coil but when key back to run it runs thru the ballast and if OPEN does not make it to the coil

I had this happen on my 510 when it would run in the START position but not in the ON.  I reconnected the plug in back and was done


But sinece no gas to carb this is simple.


I see a Weber Carb in the future. alot simplier

Edited by banzai510(hainz)
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Went for another round and she stayed alive! but then I smelled strong stench of Gas..I peek over the hood and gas is spraying everywhere from the fuel pump. New pump doesn't fit? Maybe I'm missing a bracket or something.. Here is the pump I ordered https://www.oreillyauto.com/detail/c/import-direct-fuel/fuel-delivery/fuel-pumps---tanks/fuel-pump/fuel-pump/83db8e3f0135/import-direct-mechanical-fuel-pump/idf0/m23077/v/a/8232/automotive-truck-1976-nissan-620-pickup?q=fuel+pump&pos=2


So I swap out to my old pump, fill the float chamber & boom we're back to her dying after she uses the float chamber fuel. 



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does this truck use a return line.


well where is it squiring out of the pump?

I have run those pumps before and never had a bad one but I always get a stock one to put in cause I hate looking thet them. but you put the white spacer between the head and pump.?


you can always pump it by hand and see if it shoots gas out and just leaks out the side i guess.


clamps tight????

Edited by banzai510(hainz)
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2 hours ago, banzai510(hainz) said:

but you put the white spacer between the head and pump.?





Smokey as hell exhaust & my stereo no longer has power but the engine is alive!!!

Thank you to everyone, seriously couldn't have done it without y'all cause i'm mechanically retarded.



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