I've had quite a few PITA jobs over the years, some harder than others. Heater cores can be a problem. I laugh now but cursed Ford and the mechanic the prior owner of my 93 Aerostar who changed the spark plugs. He decided he couldn't do the right side and left side rear spark plugs. They were tough no doubt, but not tough enough to change only 4 out of 6 spark plugs. Morons like shouldn't be in business. I know it was professionally done too because the prior owner had the receipt for the "tune up." I took out 4 Autolite plugs and 2 Motorcraft plugs when I tuned it up.
Around 20 years ago, my wife's friend's husband
had a no-start on their Aerostar with the 3.0. He was sure it was the fuel filter, and had bought a new one. Of course this was in the winter, and a fair bit of snow had drifted under the van, and the fuel filter was underneath. At least the clearance was pretty good. So I changed the filter, but the van still wouldn't start.
So, on to troubleshooting. The spark was very weak. There was this little hatch near the bottom of the centre console that gave limited access to the distributor from inside. I changed a very worn rotor. Can't remember for sure if we changed the cap too, but I think so.
Then it was on to the plugs. With some difficulty, I changed the two front ones.
With two new plugs, the van started fine.
Conversation back at home was something like this:
Me: Got it going. Changed the two extremely difficult spark plugs. Didn't change the other four.
Her: Why did you change the two extremely difficult ones?
Me: Because the other four are impossible!
A couple of months later, I changed the other four from underneath. It was tricky, but not impossible.