We all love the diagnostic treasure hunts we regularly feature in these pages but sometimes the faults are more basic – and not at all electronic.

I was reminded of this today watching a YouTube video on the restoration of a WWII Grant tank (at the Australian Armour & Artillery Museum). They had previously started it (rebuilt engine) and it ran fine. Next they did a run outside to “stress” test the engine with some load. It was the builders who got stress tested though as when the engine had any load applied huge clouds of black smoke came out the exhaust – unburnt fuel. Not a good look!

Back to the workshop remove the new exhaust (in case there was too much back pressure) and the air filter. Back outside and a very similar result producing an effective smoke screen.

Back in the workshop again and remove the first section of the intake manifold and there is a very dirty and very stuck piece of rag. Turns out someone diligently stuffed the turbo intake with a rag during the rebuild to prevent any ingress of foreign material and it never got removed when reassembling. Luckily it was in the turbo outlet and got jammed in the intake manifold, so no long-term damage done.

Cloth removed and the tank ran as expected – simple solution after missing a rather obvious step in the process – which I am sure most of us have been guilty of at some time in the past.

If you want to watch the video, the link is https://youtu.be/6wwVj29CW60.

There are a couple of other goodies in their channel where they visited a vast yard in Victoria full of old military gear and recovered three more Grants to rebuild or use for parts – literally chainsawing out trees growing up through them!