If the engine was pressure washed, chances are good something got wet that shouldn't have. When ever I clean my engine I only use hose pressure and let the water run where I want it to. So it takes a bit longer to cut through the crud, no biggie. If your Dad did use only hose pressure, he may have watered something accidently, it happens. Good news is it should dry out.
Make sure there is no moisture on the inside of the distributor cap or rotor, not sure if the trigger points can be affected by water or not, make sure there is no water under the plug resistors cause spark to go to ground. Same for the coil wire ends. I think it is all related to the washing.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.