Engine Primers in P337H - Are they used ?

[SierraYankee]

Hi Folks;
Please refer to attached picture. The two lower knobs [below the T-handles for pressure dump valves] are listed as Engine Primers in POH. No mention in any checklist. Did not use for engine start, or air-start. Aux Fuel Pump is used for priming before starting engines.

Anyone know a definite answer ? Are they for standby use if ship power lost & handprop ?! Were they disconnected per SB ?

THANKS