355 No start no check engine or slow down light

Hi My 1997 UK F355 GTS wont start Motronic 5.2

Battery went flat over holidays and after full recharge car fails to fire.

Battery fully charged and cranking as normal
Alarm dissarmes light solid and not flashing
Engine check & Slow Down light NOT comming on with ignition
Battery voltage at engine ECU Fuse 30 and swapped relay M
Air pump starts when ignition turned on? (now disconected)

Everything works on vehicle as it should except lights from engine ecu?

Am I missing a simple ECU reset? car did it last summer and corrected its self and has been ok since. Battery isolator off over night tonight will try again tomorrow

Appreciate advice before I start stabbing in the dark.

Many thanks in advance...

 

got spark?
got fuel pressure?

 

No? because engine ECU appears dead?

Even before cranking?

 

check spark while cranking. is it there?
check fuel pressure after key on. is it there?
That is the first step in diagnosis. Until you do that, there is no direction as to how to proceed.

 

The engine ECU, is dead...

No engine management lights on dash with ignition turned on

 

Was the car jump-started in the process of trying to get it going? I've heard sometimes jump-starting takes out ECU's.

 

update; car now repaired and running

Corroded electrical connection on fuel injection relay terminal. Found while doing pin out and jumper tests, although relay clicking it wasn't supplying voltage to ECU

Cleaned fuesbox with electrical contact cleaner & water dispersant

NB if air pump starts with ignition turned on before engine being cranked, it may signal no power being supplied to injection ECU?

Many thanks to all on forum for help and advice

 

Thanks for sharing