Electro Pneumatic Start Valve - OVERHAULED
On Yak 52 this valve is located ahead of the pilots left foot and is mounted against the rear of the firewall, above the voltage regulator.
If you are having trouble with yours, it's no secret these were a 'marginal' design - by which is meant you'll need a solid 28v in the battery and at least 40 bar of Air Pressure to make a successful start, because the spring is only overcome by a combination of Electrical and Pneumatic force, simultaneously applied.
(The unit pictured is a used example and does not depict the true appearance of a Factory overhauled unit in its original packaging.)
A version of this valve exists without the manual lever shown in the second photo. Being mounted on the firewall, this WAS something you could operate with your foot in a 52, but could not reach in a 50, hence Yak 50 start valves ( while interchangeable) don't have the lever.
All Electrical Items are sold without warranty and cannot be returned. All sales are final. Thanks for your understanding.