A Replace solenoid

Q - There’s a solenoid that appears to have something to do with the starter motor circuit on my old diesel engine. It looks in poor condition externally and I’m wondering if the vehicle will start if it stops working, or if I should buy one as a spare just in case?

A - After travelling through very remote parts of Australia over the years I have learnt one thing and that is to ‘bin’ suspect parts. In the instance of this solenoid I would do so. Worse case if it failed on a trip you could probably jump a bit of metal across it to start the engine but this would be emergency style. Best to replace new now.