I have fitted a secondhand engine to my 2015 mk7 1.5tdci, I had the engine running, once I joined the cat to the rest of the exhaust, I started it, it ran for a few seconds the died on me and now won't start, what have I done wrong?

What happened to the old engine?

Just wondering whether there's potentially a blockage in the exhaust before we start looking at the engine itself.

The cam belt went, and as it's a interference engine, I opted for another one with 70k miles less, lol, it was running ok before I pot the exhaust on, I've just taken it off from where I connected it and it won't start either, I am not getting any codes either, I am at a loss, thinking about getting a mobile mechanic out if I can't work it out

1 hour ago, NDavies said:

The cam belt went, and as it's a interference engine, I opted for another one with 70k miles less, lol, it was running ok before I pot the exhaust on, I've just taken it off from where I connected it and it won't start either, I am not getting any codes either, I am at a loss, thinking about getting a mobile mechanic out if I can't work it out

I feel like the exhaust is probably just a coincidence.

Has the battery charge dropped while you've been working on it?

Can you hear the tank pump priming?

Yes the exhaust was just coincidence, 2 10A fuses had blown in the engine bay, I have managed to sort it out, and it's running again now 😁so I am nearly ready ti send it for the MOT and get it back on the road, thank you for replying to my message