mystery sound

Can you get under there and pinpoint the noise.

looks like it is coming from something under the van at the point where you put in the gas.

Could it be coming from your tank? As in your fuel pump buzzing or humming? Pump will run for a few seconds after you shut the vehicle down.

the noise begins about 10-15 seconds after I shut off the van...sounds like a generator beginning to run.

Does the vehicle have air shocks in the rear, possibly a compressor running? Maybe the van was modified for handicap accesibility and was equiped with air shocks.

How long does the sound last?

I don't know if it has air shocks. This just started happening about a month ago. It runs for about 5-10 minutes then stops. Another post asked if the van had a self-leveling suspension and this is the compressor runnng until the air pressure is boosted to the point that levels the van...said to check for leaks in the hoses to the rear shocks. This sounds like what you are asking also. I'm obviously not fixing this myself...just hoping it isn't a major thing and wondering whether to ask the mechanic or go to the electrical repair shop.

Yes, more than likely it is the compressor running overtime, it is normal to run for say, 5-15 seconds but 5 minutes is way too long, have it checked out for possible leaks, bad shocks, level sensor etc.