Troubleshooting a Triac Motor Control Circuit
Be sure to use plastic caps ( polycarbonate or similar ) for low impedance filtering of spikes from motor when switched off at peak voltage.  THis would likely be random and determined by timer in pump circuit. An improved design would also have zero-crossing triac cut-off connected to manual switch for solder iron pump. So 1) verify Plastic cap is same 2) check for pump motor shutoff spikes

Scope to verify.