Have you ever fired up an engine that sat for a year? What about five years? What about 10? What about a motor that you’ve rebuilt yourself? If the answer is No, then you’re missing out on the single greatest feeling in all of car-dom. If you’re not convinced, just watch this.

I recently found myself watching the , run by friends of mine. In the latest clip, which chronicles their full restoration of a Land Rover Defender 110, Lisa and Jacob fire up the off-roader’s 2.5-liter 300Tdi turbodiesel engine for the first time in two years. Their excitement is palpable:

Why do we feel this way when we fire up an engine? What is it that brings Lisa so much joy that she jumps up and down and yells with excitement?

“Oh mein Gott, oh mein Gott,” Jacob exclaims, placing his hands on his head as he smiles. Lisa looks into the engine bay at the now healthily beating heart of her machine, claps, and drums on the vehicle’s fender in excitement. It is truly special moment.

Watching this clip reminded me of the times I’ve experienced this euphoria. There was the time my friend Freddy and I got my 1948 Willys CJ-2A’s Go-Devil engine running

More recently, there was , a vehicle that I’d bought sight-unseen and non-running. The first time I heard that van’s VM Motori 2.5-liter turbodiesel idle was magical:

Then there was my , which needed a fuel pump and some ignition bits to get going:

Here’s my pickup after it had sat for five years, and I’d finally gotten the ignition and carburetor dialed in:

Here’s how excited I was when I managed to get , my 1976 Jeep DJ-5D Postal Jeep, running for the first time after I’d replaced the cracked cylinder head:

Here’s my friend Brandon with me and a reader named Matt firing up Matt’s Jeep Cherokee Briarwood, which had been making some terrible noises prior to my tightening the flex plate bolts. :

No matter how stressful your life might be, once you’ve heard an engine run for the first time under your ownership — or for the first time since a major overhaul — your worries disappear for just a few moments, and your brain becomes saturated with pure elation. Here’s I am with my friend Brandon firing up my ’s new engine last week:

Driving The Jeep Cherokee Golden Eagle For The First Time In Years

That brings me back to my question: What is it about firing up a long-sitting or recently rebuilt motor that instantly fills us with joy?

Obviously, the simple answer is that it means you’re closer to driving the car; of course it’s exciting to drive a car for the first time in years. But there’s more to it than that. The reason why people yell, high-five and jump up and down in joy has quite a bit to do with mystery, I think.

If, just prior to my trying to start the cars shown above, someone had told me, “David, this engine will 100 percent run perfectly as soon as you turn the key,” then I don’t think the situation would have been nearly as thrilling.

There are so many components in an internal combustion engine, so many ancillary bits and thus so many failure modes. Does the ignition switch work? How is the wiring from the switch to the starter motor? Speaking of which, how is that starter motor? How are the teeth on the flywheel? How’s the engine’s valve timing? What about its ignition timing? Does the ignition module work properly? How are the spark plugs, plug wires and distributor? What shape is the carburetor in? Is the intake manifold sealing properly? Are the accessory drive belts and pulleys in decent order? What about the engine internals? Are the bearings and cam lobes worn? What about the rings? Is the exhaust system tight?

The list goes on and on.

Given so many different things that can go wrong, hearing an engine run for the first time brings relief that manifests itself in true joy. Along with the knowledge that your car is one huge step closer to being driven for the first time in a while, it is the greatest joy in the whole of automobile enthusiasm.

Everyone should experience it.