I am a mechanic specializing in American and Japanese cars; this is the first time I work on Mercedes. Problem was that car was passing water to the oil pan. I changed both heads and all gaskets but upon finishing the car doesn't start. If I push the accelerator pedal to the floor it starts but if I release it the car stalls and doesn't start. I take the spark plugs out and find them full of raw gas and if I clean them the car starts. There is good current to the spark plugs, the fuel pump has good pressure. Can anyone help me please?

yo soy mecanico de carros americanos y japoneses pero es primera bes
que trabajo en merzedez el problema fue q paso agua al aseite y lecambie las dos cabesas ytodos los empaques y ya lo termine pero ahora no prende solo sile detengo el pedal asta el fondo prende siselo suelto se apaga y ya no prende le quito las bujias y estan llenas degas silas limpio buelbe a prender ay buena coriente enlas bujias la bonba tiene presion de gas algien que me ayude por for