Lister LR1 will not start after a catastrophe

Hi all.

I made a silly mistake today. My Lister LR1 was running sweet this afternoon and after just over 30 minutes I suddenly remembered that I had not topped up the oil in the air filter (its an oil bath type). Without further ado, and while the engine was still running, I whipped the top off and poured some in. When I replaced the top the immediate effect was that the engine suddenly speeded up to somewhere approaching twice its normal sped and immense clouds of white smoke billowed from the exhaust. I immediately guessed that I had over filled the air filter and the excess was being drawn down into the combustion chamber and was being burnt together with the normal diesel thus causing the over speed.

Panic. How to stop the engine. The stop lever had no effect. In retrospect it wouldn't would it. At the speed the engine was running – and still, it seemed getting faster I did the next thing that came to mind. No, stupidly I did not remove the offending air filter. I operated the pressure relief lever. This holds the exhaust valve open. Eventually, this worked and the engine slowed down and eventually stopped. I say eventually as it must have taken about 15 seconds.

Now everything has cooled down and I have the air filter oil level correct the engine will not start. I have bled the fuel system, in case I had somehow let air get into it although I don't see how. So now I am thinking the worse. Have I burnt the exhaust valve out? All (sensible) suggestions welcome. Adverse comment expected.

Help!

Cheers

Alan