Bought a Troy-Bilt 2550 from Lowes today. Working fine until I put the detergent siphon in a proper mixture, made sure inlet was submerged. Pressure relief valve 'popped' almost immediately and now NO flow while engine is running. With engine off and water still on it will flow at garden hose pressure. Removed detergent siphon from pump, no change. Let it sit to cool, no change. After cooling and restarting still no pressure and relief valve opens after 20 - 30 seconds. Guess I'll return it tomorrow, but any ideas in case I see it again?