MK3 Golf GTI not starter/runner help needed.

Does it flood all 4 plugs , or just 1 ?

Could it be a stuck fuel injector or fuel pressure regulator ?

Coolant temperature sensor busted and making the ECU think it’s much colder and thus over-fuelling?

Also, have you tried a noid light on an injector to confirm that they are pulsing and not just “on” when cranking. Used to be a thing with GTIs (though possibly mk2, not mk3) that if engine earth was lost it would earth via injector wiring and cook the injector drivers with exactly that effect.

did you hit the OK button?

I've found what happens with my old car is as follows:

1. Leave it sitting for 6 months without starting

2. Try to start it, does not start on the first few cranks so keep trying

3. Dump a ton of fuel into the cylinders

4. It will never start


The fix is to:

1. Disable the fuel pump and ignition system

2. Take out spark plugs and burn the tips with a blowtorch or on a gas cooker. Initially the flame will be yellow which indicates you are burning off the petrol. When the flame goes blue like the gas flame the plug is clean and ready to refit.

3. Before fitting the plugs spin the engine over 10-or-so times to blast all the excess fuel and any other curse word out the holes.

4. Refit the plugs, reenable fuel and spark and try to start it again. Hopefully successfully!

Back to basics then... you've done the compression test so that's good.

You may have checked these things already but have you verified that:

1. Exhaust is clear all the way through and no blockages?
2. Intake is clear all the way through and no blockages?
3. Fuel return line is not blocked and can vent fuel back to the tank?

Like the easy-start suggestion. Have you ever had so
much as a cough from it?

We did own a P-plate one of these for several years which was mostly fairly well behaved, but did go through a period of random refusal to restart when hot. That was eventually tracked down to a dry joint on the fuel pump relay/engine management relay (though not before its eviction notice had been signed), so unlikely to be the problem in your case. I don’t recall any ECU pond/wetness issues while hunting down the problem.

Only other thought is that I’ve found dome NGK spark plugs to be rendered useless by a single fuel flooding event. New/lightly-used being worst affected.