Yeah, I'm with HDR and Bullfrog, you shouldn't need to install sparkplugs just to diagnose a no-start. Perhaps if needed for maintenance, but I'd suggest to diagnose the problem first. Do you know if the engine ran when it was parked or was the van parked because it didn't run back then? The diagnostic process is still pretty much the same, but we'll just know more if a possibility of a hard failure and it might point us somewhere. Knowing the history just helps to narrow thought processes. For example, it would be helpful to know if the previous owner went through a bad breakup and an ex sugared the gas, put water in the tank, or some other shenanigans. Did anyone try to do their own tune up or disassemble something and couldn't get it back together right, etc.? Do we know if it had an overheating problem before parked? If it was running absolutely find when parked we can eliminate certain issues and look elsewhere.
A gas engine needs fuel, compression, and spark at just the right time to start and run. A squirt of quickstart into the throttle will examine the possibility of fuel as the issue. Adding quickstart, if it starts briefly or sputters and dies that tells us the ignition system is good, you'll know the problem is fuel delivery or engine controls and can look more into that. If it doesn't even sputter or pop, then we check for spark. Pull a wire or coil at the sparkplug and hook it up to an old sparkplug clamped to ground, then crank the engine and watch for spark. A spark means ignition is most likely good (trigger/coil are working), although timing might still be suspect. Last thing and least likely would be to check compression. If compression is bad that would indicate a hard mechanical failure (bad news). Again, if you know it was running fine when parked we can eliminate mechanical failure as a possibility.
Fuel pumps are usually pretty quiet and only get noisy when they go bad, or if the filters are restricted and the pump is laboring. Pumps and filters are a pretty common thing. Since you're hearing the pump running, at least that means we're getting power to the pump. Instead of buying sparkplugs, I'd look to change out the fuel filter and check the contents for any flecks of metal. Just tap the filter with the inlet down and as the residual gas comes out you'll see flecks of metal or just clear gas. Clear gas is good, but the presence of metal flecks means the fuel pump is chewing itself up and needs to be replaced (before it fails and leaves you stranded). Unfortunately, if you see metal that would mean dropping the tank to change the pump.
