"My Carb Needs Priming" Issue

[retread]

Hello All,

I followed Pinhead's awesome Youtube Vids and rebuilt the original carb on my 1978 fj40. His tutorial and guide is amazing and really helped me get this done.
However, I have two issues. The unit has to be primed by hand to start. Once started it idles and runs better than before. But, once stopped and sat overnight, it must be primed again.
Before the rebuild, the carb would start without priming. So, what have I done incorrectly? Any help would be appreciated.
Also, the bolt/vacuum port that attached the base to the body was just a replacement bolt someone had used over the years. We tried drilling it out, to no avail. Anyone know what this port facilitates?

 

[php74]

Can you hear the fuel pump working?

 

[retread]

Thanks php74. Once the carb is primed, the engine idles continuously, it stays running. I assumed the pump would have to be working for the vehicle to stay running.

 

[php74]

Oh gotcha, I get it now, bad reading comprehension...if you shut it down and say, wait 1 minute, would it start again?

 

[php74]

Also can you drive it or have you only had it at idle?

 

[Michael Hanson]

Hi, Any vacuum leak between carb and its base ? Float sticking ? Mike

 

[retread]

It will start after several minutes. I have not driven it. Just idle, but the engine will rev. I see fuel in the view window and it is about half of the window. I imagine the float could be sticking. How could I test if there is a vacuum leak? Thanks for your help.

Mike

 

[thebigredrocker]

I have't tried it yet but I've read Pin_head say he likes to use an unlit propane bottle to search for vac leaks. Obviously while your rig is idleing you can kink the hose to the brake booster and get instant confirmation if it's leaking.

also you could try this

 

[Curt]

What do you mean hand primed? pour gas down the carb?

 

[Pin_Head]

Fuel creeping out of the bowl is a common problem even in carbs that have not been rebuilt. My guess is that it is due to the increased surface tension of reformulated gasoline. It drips out of the idle port, so my next experiment would be to press a small piece of teflon tubing into the idle fuel hole at the top of the bowl side. It can't creep over teflon. Maybe polishing the inside of the hole with 1200 grit silicon carbide would help too.

 

[retread]

Yes Curt. Thanks Pin_Head. I just feel it might be something I did during the rebuild in that we did not have the problem before the job. I guess I can try the Teflon Tubing. I hate to keep asking, but mechanically, what holds the fuel there in a perfect world? Perhaps that could help me realize the problem if it stems from the rebuild.

 

[Pin_Head]

Gravity holds the fuel in.
There is also a vent pin hole at the top to prevent siphoning. If the vent hole is plugged, it will siphon but you checked all the vents holes, right?
I have seen it enough on good carbs that I think it is creeping over the top by surface tension, just like when you put a strip of paper into a glass of water with the end hanging over the side. Water will wick up the paper and over and drip on the table. It is possible that cleaning it out left the surface more rough so that the fuel is more likely to creep up and over.

 

[retread]

Thanks Pin_Head. The surface is indeed much rougher from the dip. I will take the top cover etc.. off and see what it looks like. I have seen some folks say an electric fuel pump helps this issue. As a final thought, would that be worth considering?

 

[Pin_Head]

No, but obviously it would prime when you turn the key on.

 

[pb4ugo]

Is your accelerator pump working?

 

[Curt]

Is your accelerator pump working?

That is what i am thinking, look down your carb and press the accelerator. You should see a stream of fuel. This could be blocked by some debris during rebuild. Pass mono filament through there to ensure its clear.

 

[Pin_Head]

There is no fuel left to pump when the bowl is empty.

 

[Curt]

He claims the carb shows half way on the sight glass, not sure if that is before or after trying to start the vehicle though.

 

[sggoat]

Do you have the orig exhaust manifold? If so, does the truck have a heat shield to disperse manifold heat away from the carb? My 77 suffered from heat related boiling of the fuel out of the carb(even after the rebuild following Pin_Head's vids){not related, by the way} Caused a lot of excessive cranking to finally get fuel back into the bowl and past the apparent vapor lock in the feed lines.
The ultimate fix for this was headers(even after installation of a carb cooling fan that worked so-so), and a secondary, parallel elec fuel pump.
Now, if the rig sits idle for more than a couple of days, I just start the elec pump for about 15 seconds, one pump on the accel, and she fires right up. If the truck has been driven for more than a few miles(well up into oper temp) and then shut down(even for just a few minutes) the underhood heat dissipates quickly(usu. drops below 190 in less than 5 minutes)--restarts usually in less than one full revolution

 

[algeeba]

Kind of hijacking here.

Pinhead, are those long flexible spray nozzles like for carb cleaners made out of Teflon or plastic? Can they be used?
Also, what about the fuel hole on the secondary side, polish that one also?