Re: 1938 Super 8 1605 - adventures with a newbie

Posted by HH56 On 2023/8/14 12:48:16

I am also a believer in having a switch controlled electric pump located near the tank. There are two type pumps and both work well. The solenoid type will allow the mechanical pump to pull thru when it is off whereas a rotary type will generally require a dual bypass path with a check valve in the bypass line so fuel can be pulled around the electric pump. Downside to the solenoid type is noise, and to the rotary type, the extra plumbing needed.

As to your mechanical pump, one thing that has caught others is diaphragm tension. Not knowing exactly how the diaphragm is actuated in your specific pump it may be a non issue but on other pumps it is not. In addition to extreme wear and possible damage to the diaphragm, a tight diaphragm is unable to move full range and can provide too little fuel delivery per stroke or with one having extreme tension, the fuel delivered to the carb is often at too high a pressure for the float valve to shut off reliably.

If you did not have the arm pushed fully down to position the diaphragm at maximum travel before tightening the screws holding the halves together that might be something to try on the rework.

If your pump is the type where the arm is directly worked by the cam you might measure the lobe for any wear to make sure the cam is moving it full stroke. If there is a pushrod involved also make sure it is not worn so not delivering a full stroke.