ECU location? water? engine wont start

[manc]

Hi, Could someone tell me where the ecu is located on the MK3?

My petrol 1.4 stopped on me after driving through a deep puddle and wont start, it has fuel and a spark at the leads, I've checked the pressure regulator and every connection I can find under the bonnet and all the relays but think it's maybe water on the ecu connection, if I can find it!!!!!

This happened before in torrential rain and I fitted a new fuel pump and filter which seemed to cure it but I now think that water on the ecu might have been the cause and dried out while I was waiting for the pump.

Help please

[adamjowens]

isnt the ecu unit thing under the rear seats on the inside of the car? in my mk3 theres something there anyway! looks like an old radio unit
maybe u got water in the other bits n bobs like the air filter or the force of the water pulled a sensor out of place?

[Crasher]

The ECU is under the windscreen in the plenum chamber and they don’t get wet. If you have fuel and spark it should run so how about the possibility that it pulled water into the engine and hydraulic locked? What about getting a fault code read done?

Adam, the ECU under your back seat means that you have a pre 95 car with ABS or an automatic.

[manc]

Hi Crasher,

The engine turns over OK I have a spark and the plugs are dry which makes me think it's water in the ecu playing games with the single point injector, plus my cover doesn't fit that well of the said plenum chamber.

Short of taking the carb/injector cover off and seeing if it will try to run on some cold start squirted in there I'm thinking it's the ecu???...

... but I'm open to suggestion, I did have an ignition coil fail but that was a couple of years ago and then it would start but not drive off.

[Crasher]

If it was water in the ECU you would not get a spark. What about a fault code read? Can you hear the fuel pump running? The most common failure is the distributor hall sender but you say you have a spark.

[adamjowens]

Adam, the ECU under your back seat means that you have a pre 95 car with ABS or an automatic.

ah your spot on mate, automatic all the way

carry on!

[Crasher]

That's the box ECU.

[manc]

The problem seems to have been water on the ecu contacts as I had the ecu out, disconnected it and sprayed the connector with an electrical contact cleaner and it started!!!

The rubber edge has perished on the cover over this area (VW want a fortune for one of these covers) and I think it had let water in, plus the loom was also sloping downhill towards the connector so any water falling on the loom would run towards the connector so I have altered it's route to provide a drip loop and put a bead of silicone sealer on the edge of cover for now.

Very happy at solving this one.