Dodge Brothers Club

Having trouble figuring out why fuel isn't being drawn from my fuel tank into my Stewart Vacuum Tank on my 26 DB Sedan. No restrictions found in the fuel line, no inlet filter screen.I have tried two sets of tension springs and this hasn't corrected the problem.In comparison with my spare vacuum tank mechanism ( thks Al ) the only difference I can see is mine doesn't have the tension spring on the float shaft (see photo). All fuel and vacuum lines had been replaced by the previous owner and along with the fittings appear in good repair.The vacuum tank top gasket appears in good shape (paper though not cork) as well as inner tank and flapper valve. Have a nice original gas cap that came with the used tank I purchased a while back (thks JT) the vent hole is open and the cork gasket redone. The engine makes good steady vacuum and runs well when I manually fill the vacuum tank with gas but runs out before switching to vacuum mode, no gas showing in the clear glass in line filter I installed. Before I attempt removing the pinched expanded end of the brass pins to better inspect the needle / passage blocking valves appreciate any suggestions on diagnosing the reason for this problem. Thks Ken DBC 7051( thks Howard with help in posting photos )

Get the reprint of instructions from the DB club store, it explains how to troubleshoot vacuum tanks.

When the vacuum tanks is full the float should open the vent valve and relieve the upper chamber of vacuum so the fuel can drain into the lower chamber through the flapper valve. A leaking vent valve won't permit suction to the fuel line. If the vent valve is good but the flapper is leaking, the vacuum will be equally directed to both the carburetor fuel line and the fuel tank line.
Try putting a pint of fuel in the vacuum tank. starting the engine and plug the vent tube with your finger. If the engine continues to run but loads up with too much fuel until you allow the tank to vent, the trouble is probably the vent valve or mechanism that trips it.
On speculation I'm thinking that the flapper valve could be tested by plugging the (1/8"NPT), port that goes to the fuel tank and attaching a vacuum cleaner, (duct tape and ingenuity?), to the engine side vacuum port. Once done, an empty vacuum tank should not suck a, (small), piece of paper against the carburetor outlet port.
It may be too late for this year but remember that nothing will please Mum and the Munchkins more than finding a big box of DB parts under the tree.
Happy Festivus.
Nat

Thanks Nat, I did some more testing and vent valve wasn't sealing. When I took the vacuum tank top off there was a brass valve seat on top of the vent valve ?

It's hard to see the vent valve seats in the shop manual pictures. I was thinking this valve seat was a correct part, but was on the wrong side of the valve head ! My oldest son ( over for a Christmas visit ) determined this part didn't belong and the small valve seat (correct part ) was still in place.

The vent valve was getting stuck in the open position ( valve stem is bent; not sure how that happened, possibly jamming on the incorrect valve seat ? ) see photo

Anyways, filed the top pin and removed the washer and did the same with my spare vent valve. Switched out with the straight vent valve ( soldered washer back on). Made up new gasket ( Fel Pro 1/32 Rubber-Fiber sheet ) and reinstalled with out that brass valve seat and problem fixed. Thanks to Doug for letting me run the steps I was trying by him and also to Rodger Dodger for his thoughts and encouragement to get it fixed.

Ken