Vacuum Tank performance

[Wheelmang]

My 1926 DB 6V continues to have trouble staying running. All electrical, coil, primary wire, plug wires, points, condenser are replaced new. My carb is totally rebuilt. It will start up just fine although I need to keep it running long enough to get to the distributor and fine tune timing. It runs just long enough for me to get it off choke and timing advance/retard and smooth out. It then starts to race up and sounds like it runs out of gas and will not start again. At some point a PO has placed a fuel filter in line. When I get ready to start it up I pour a couple ounces of No E fuel in the top of the vacuum tank and replace the cap. This is done as it does not appear to have run long enough to pull gas from the back to fill up the fuel filter. The gas tank has been removed and is completely clean. The gas line is clear. I have blown it out from the front and the back ends and there is no restriction. 

What are the characteristics of a failed vacuum tank?

Should the vacuum tank have sufficient draw to pull fuel through a filter?

Should I be looking at a 6V electric pump?

Thanks all for your valued opinions.

Paul

[JFranklin]

You need good vacuum to pull gas from the tank. you could remove the line from the tank and affix a gauge in its place to check.

[R.White]

I hesitate to criticise the vacuum tank set up because I know that if you have a good working example they are very reliable; more so than an electric pump... but I too have been having problems with my (Stewart Warner) vacuum tank.  The problem that I have (I think) is neat fuel being drawn down the vacuum line directly into the inlet manifold so a lack of suction is not to blame. In my case  I suspect the inlet valve in the top may be faulty.   If you have air tight fittings there should be no problem in drawing fuel from the tank  - after all, that is what it is designed to do and was successful for many makes of car over many years.  

 

Ray.

[MikeC5]

I do have one of those clear case fuel filters spliced in the line from fuel tank (under rear floorboard for access) on my ‘25 and vacuum tank has had no problem pulling fuel.

[JFranklin]

Ray you may need to check the float for leakage. the float rises to shut off the fuel.

[JFranklin]

here are some pages of info to look at.

[zeke01]

My two cents worth: check the unit for air leaks and check the flapper valve. Pot metal tops are notorious for leaking air. Zeke

[Taylormade]

Why not hook up a small, gravity fed fuel tank?  If the car keeps running, you'll know it's the vacuum tank that is the problem.

[Wheelmang]

On 12/29/2017 at 1:26 AM, Taylormade said:

Why not hook up a small, gravity fed fuel tank?  If the car keeps running, you'll know it's the vacuum tank that is the problem.

I keep forgetting the simplicity of these cars. That just makes a whole lot of sense! Thanks.

[hddennis]

[Wheelmang]

Special thanks to JFranklin and HDDennis for posting the manuals. After reading through them a couple times each I stumbled onto what is likely the problem. When I removed cleaned and reinstalled the gas tank I replaced the disintegrated cork seal under the gas cap. Did not realize it was supposed to have small holes in it. 

Can someone also tell me where the vacuum line for the windshield wiper is supposed to connect?

Thanks for your assistance. 

[Ron Lawson]

Most that I have seen have a T piece in the top where the pipe from the intake manifold goes to

[stakeside]

IF AN ENGINE IS GETTING TIED AND WORN DOES THE VACUUM DRAW ALSO SUFFER? IF SO THIS WOULD EFFECT THE VACUUM TANK.

SEEMS THAT POOR VALVES WOULD HAVE AN EFFECT.

[platt-deutsch]

I would remove the filter and see if that makes a difference. It requires very little vacuum to raise the gas 4 ft.