Old and new Briggs & Stratton Pulsa Jet carburettor fuel pump diaphragms.
The old diaphragm was off a 30 year old 5 HP Briggs & Stratton L-head engine that refused to start after sitting in storage for several years.
The cause was simply due to the old pump diaphragm stretching and losing the ability to compress the spring and in turn pressurise the fuel. The flapper valve over the inlet port had also stuck closed, which would have prevented fuel from flowing even if the diaphragm had not been stretched.
I always like to flush out the fuel tank and change the diaphragm on all second hand B&S engines I get. Saves trouble in the future. Also diaphragm's and gaskets are cheap.
I also like to do a cylinder leak down test on second hand engines to see what condition they are in. I often find they need the head removing and require a good de-carbon and clean up of the valves.
Yes, I agree. Preventative maintenance will always maximise engine life and is a greatly neglected service task in this day of throw-away, maintenance free products.
These diaphragms were certainly used on B&S 8, 10, and 13 Series engines. They were a Code 1 part - meaning, they were required in any general overhaul of these clever carburetors.
As you and beantin have said: the diaphragm and gaskets are part of any service on these carbies.
After diagnosis of fuel problems, the diaphragm was the first port of call after contaminated fuel.
