87 XJS V12, started up just fine, drove it to the local gas station, put in $50 of 91, now it won't start. Luckily it was only 1/4 mile from home, we towed it home.
Here is what I've checked so far,
Fuel pressure, 35 psi at the rail, holds pressure well.
Wire 18, has continuity, not shorted to ground
Checked all the ECM grounds, no issues
After it's sat for a while, when you try to start it it will fire on a couple of cylinders but after that, just cranks
Checked the coolant temp sensor from the ecm end, normal reading for the prevailing temperature
Cleaned the power resister plug and terminals
Replaced the "new" ignition amp with an unknown used one, no difference
Plugs, plug wires, cap and rotor are all new, timing was set to 18 degrees at 3000 rpm, all over the winter
What did I miss? ECM?

 

Bad fuel? Injector loom failing?
Try diabling the fuel pump and squirting lots of easy start down the intakes and see what happens.