2.5tdi not starting

[Kevin o'neill]

I washed my 2003 a4 2.5tdi in a car wash for mot, the wash was less than five minutes from the test centre but when it came out it wouldn't start, rac tried but to no avail, their computer says no communication with fuel injection pump, when I discovered that the ecu tray was flooded, this car had engine replaced, the original injectors and fuel pump were fitted to the replacement engine, iv been driving it for two months with no problem, can anyone help, iv dried out and replaced the relays

 

[Sturat]

If i understand you right. You found out the relays were in water after the rac guy had looked and now after drying out the original relays it still won't start?
If this is correct I'd get replacement relays.

 

[Kevin o'neill]

Blew them out with Compressor and contact cleaner, three times, bled her, and she started, just a bit of information that my son discovered, no'28 fuse to the tank pump has no power going to it when the ignition is turned on, it gets power as soon as you crank the engine, this was very misleading as you'd think that as soon as you turn the key it'd have power

 

[Sturat]

As far as I'm aware, the crank and cam sensors have to be working whilst cranking engine for the injectors to work. Maybe the fuel pump is the same?
Would help if someone with more technical knowledge than me can say if that true or not.