Reply To: Fuel primer pump

[Gregory Long]

To repeat and to add to the above information;

This is a valve. it was used from the ‘teens’ up through 1928.

The teen’s and Series 33/36 cars had a pressurized fuel tank and fuel delivery system. As stated above by Miles, if the fuel system is pressurized, whether the engine is running or not, if the primer’s shaft is pulled, fuel WILL squirt down the intake manifold and drip onto the throttle butterfly.

On the Series 80/81 cars, the fuel system used a Stewart Warner vacuum draw system with a reservoir on the firewall. The fuel level in the reservoir is well above the level of the primer-valve. if the reservoir has fuel, and the valve between the reservoir and carburetor inlet is open, then the primer will dribble fuel into the intake manifold and dribble a lot of fuel onto the butterfly of the carburetor.

So, even the Series 80/81 cars can have some primer-fuel delivered into the intake manifold if the engine is not running or turning over.

If the series 80/81 engine is being cranked by the starter, significant intake manifold vacuum is created, if the primer needle is pulled, the volume of fuel being drawn/sprayed into the intake manifold is greatly increased. The engine can easily be flooded by too much primer use.

Also, if the primer leaks, the excess fuel causes significant problems.

Greg Long