Vacuum fuel tank

[WPVT]

I rebuilt and reinstalled the Stewart Warner vacuum tank in a 1929 White truck. I turned over the engine for 20 seconds or so several times, but no fuel has reached the tank. The line between the vacuum tank and the fuel tank is clear of obstructions and leaks. The vacuum line to the manifold is only about 20" long and it is also sound and free of leaks. Can anyone suggest a troubleshooting  test while the tank is still installed on the truck?  The tank and internal mechanisms were in very good shape when I disassembled it, and I was pretty careful during reassembly. The float looked perfect as did the brass parts. Is it reasonable to expect the engine vacuum while cranking to be sufficient to draw gas up into a dry vacuum tank, or do things need to be wet to function?  I didn't want to put gas in the vacuum tank first; That way if I saw gas in the sediment bowl I would know it was working.  

I suppose I could put a vacuum gauge at the fuel inlet, and that might narrow things down. How much vacuum should I have at the fuel line?

Thanks.

[Spinneyhill]

Go down a few topics to Dodge1934's topic about the Stewart fuel pump. There is plenty of information thee.

[dictator27]

Fill the vacuum tank before attmpting to start the vehicle.

[Rusty_OToole]

You have to start the engine for it to work unless you have a vacuum pump to test it with. As Dictator said put a cup of gas in the vacuum tank, once the engine starts it should suck the gas into the upper chamber.

[WPVT]

Thanks. I didn't notice the earlier post since it referred to a Stewart fuel "pump".  In reading the PDF (very helpful) I found reference to the valves possibly not working if the tank was dry. I'll add a little gas and see if that seals things up. 

[Rusty_OToole]

The engine won't run without gas and there is no vacuum unless the engine is running. You can easily pour a little gas into the vacuum tank, be sure it goes into the bottom chamber so it can reach the carburetor.

[WPVT]

Thanks. It was my understanding that the vacuum generated by cranking was sufficient to draw gas into the tank. But maybe I am wrong. Certainly a running engine would do a better job of creating vacuum.

[Wheelmang]

Just had a similar issue on a 26 DB. Make sure the small hole in the gas cap is clear.  

 

Edited January 4, 2018 by Wheelmang
added jpeg (see edit history)

[WPVT]

I did some testing and found that cranking the engine with the starter produced very little vacuum at the tank. Certainly not enough to draw gas. So I checked vacuum at the intake manifold and found the same. Conclusion...starter cranking cannot generate enough vacuum to draw gas, even with everything working as it should. 

So...I primed the vacuum tank, and started the engine. Everything is working fine. Idle isn't quite as smooth as before, but maybe there's a tiny vacuum leak somewhere. I'm off the electric fuel pump and running on the vacuum tank. First time in many years.

Thanks for all of the helpful hints.

[MikeC5]

Some of the SW vacuum tanks have a threaded plug in the center of the tank cap which makes it easier to add fuel.  If yours doesn't have one,  you may be able to find one that does that will fit your tank.  Perhaps if you cranked long enough with a healthy engine, it might get enough fuel into a dry tank to start but why run down the battery?  I find that I can usually go 3 weeks without starting and enough fuel will still be in there for engine to start right up.  

[old car fan]

Prime the tank,full.,You can hear the float.If your car runs,you should be hear the cycle of the tank.Pm me,i can rebuild it it ,or tell what most people miss

[a sell]

You usually will know when it is drawing gas from the tank.  The engine will run smoother.  When the vacuum tank is full and float releases - it will direct the vacuum to vent.  This creates a small vacuum leak and the engine will run a little rough.  This is normal.  While helping a friend diagnose his vacuum tank I installed a section of clear hose in the inlet piping from the gas tank.  This was on an original low milage inline 8 that ran very smooth.  It was interesting actually "seeing" the process as the tank worked so its actions were no longer such a mystery.

[WPVT]

Thanks. I appreciate your posting the reply. 

[jrbartlett]

My '29 Packard Super 8 has a vacuum tank, and I've run it out of gas a few times. After refilling the gas tank, it will pull fuel up to the vacuum tank and start the engine with a little cranking. Perhaps your White will too with a fully charged battery and good tuning.