The chamber volume is around 50cc, and the injectors are 540cc/min.  Therefore the injector could supply enough fuel to hydraulic lock in 5.5 seconds.  The inlet valve opens every second rev, so if it's cranking faster than 22RPM then it can't lock.  It should be cranking 10 times faster than that.
 
There isn't enough accumulated volume in the fuel system to supply 50cc with the fuel pump not running, so it wouldn't be dribbling in overnight either.  I've hot and cold started and driven (to get it home) a 3SGTE with a mechanically stuck open injector, and it never hydraulic locked.  It just blew a lot of smoke and smelt like crap.
 
Are you sure it's all fuel?  Coolant seeping through the head gasket or a cracked head/block overnight could and often does lock an engine, and fresh fuel injected when attempting to start will give it a fuel smell.

It definitely seems like fuel. There was 4liters of fuel added to the oil in the sump and it smells strongly of fuel. When it happens you can smell fuel coming out the exhaust and basically everywhere. Also when the issue happened and I cranked it with spark plug out, it was definitely fuel coming out the plug hole. When the car is started and running I've never had it hydraulic lock, only on starting up. It's definitely isolated to the one cylinder too. Does anyone know for sure if the Gen3 Turbo's run batched injection 1&4 or if its sequential?

Im pretty sure its batched.
 
If your worried about the injectors its pretty cheap to get them flowed
Was it your car that has extra injector added?

Mines not running any extra injectors but I've got a whole new list of problems now.
I haven't been able to get the hydraulic lock on start up to happen again. So I put the piping and all back on and took it out for a drive.
The ECU has started to register error code 47, which I can't find any info about. I clear it drive and it comes back. Also the exhaust temperature light comes on after about 1minute of driving. I pulled out the plugs and all of them are white so now its running lean when driving. Also it wont rev past 6,500 - 7,000rpm. I tried on low boost 10psi and high boost 16psi and it wont rev past 6,500rpm to 7,000rpm. I've got a new ignitor, coil, spark plugs, leads, distributor cap and button. If it was spark related I would expect it to happen earlier in the rev range when trying high boost. Might be the knock sensor kicking in because of the engine running lean? Any ideas why the exhaust temps are going crazy? The pipe is not glowing red of anything. Could it just be my ECU going nuts? It's a mines chipped ecu so no rev limit etc...

by continuity i mean checking to see if there is a circuit. usually when you check for electrical issues you usually check resistance in a wire rather than voltage.

turn you multi meter to the ohm (omega) symbal. then put 1 pointer on the ground wire for injector 1 and put the 2nd point on the ground wire for injector 4. if the multi meter has an ohm reading it means the 2 wires are connected at the ecu. if the meter reads blank or nothing it means the ecu has individual triggers.

error 47 on most toyota is traction control tps issue. and since most toyota codes are universal.....

would be weird to have traction contriol on an mr2

Cool got you on the continuity. Definitely no traction control on the car. Only the one throttle body.
I'm thinking I'll have to drop it off to an expert. Can you see any reason for why the exhaust temp light will come on now? Is it because of the heat from the lean condition? any idea why it could be running lean now? I'm really thinking the EU has gone off its nut......
 

Try a stock gen 3 ecu and see what diff that makes? You don't know what that Mines ecu has been setup for.

The car used to run perfect before the last track day at Winton. Was a 45 degree day. The Mines ECU was running fine, would rev to 8 or even 9k if I let it.
The problem is I don't have another ECU to plug into it. Otherwise I would just swap it over and see if that runs lean too. It's very odd that it was running rich enough to put 4litres of fuel not the sump and now its running lean. Without full workshop equipment its really hard to tell what is going wrong.

i have found this exact fault on 4 and 6 cylinder camrys but never on a SW20.  in all cases it was a dead ECU
the easiest way to test the injector firing pulse is with a NOID light. any good auto tools shop sell them for very little $