I have a feeling this is going to take awhile to figure out
yup. it can, but it doesn't have to. electrical problems are always tricky. At this point, I wouldn't worry about the spark plugs just yet. Your lack of fuel pressure is your main concern.
why? because there aren't nearly as many factors that control whether your fuel pump turns on. If you get that working, and your car starts, then you're good to go!
Do you have a factory service manual? It's got the wiring diagrams, troubleshooting steps, harness pinouts (for reference) and other good stuff like that.
i just deleted a paragraph i was writing on how to go about troubleshooting that the relay is getting power, and that the fuel pump itself is good by applying power directly at the pump, but it's really impossible to walk though the needed troubleshooting in a forum post.
Honestly, at this point, I wouldn't rule out the possibility that the PCM(ECU) is somehow dead. I say this for two reasons:
1) the PCM not only turns the fuel pump on, but it also controls all aspects of both injection and spark. If
none of that is happening, then it's
possible that it's because the PCM isn't doing its job.
2) Here's the kicker. the coolant temperature sensor signal goes directly to the PCM. The PCM then sends that signal to the dash. So if the dash is getting a bogus signal (super hot temperature, in this case) when the engine hasn't run in a while, then the PCM is definitely giving it a bogus signal, and that means PCM trouble.
Do you have a way to connect an OBD2 scanner to it to see if there are codes? rent one from an auto parts store, borrow one from a friend. anything? If a scanner can't establish comms with the PCM when the key is in the ON position, then that's invariably bad PCM.
If you haven't done it already, then you might try disconnecting the negative batt terminal for like 10 minutes (give time for all residual voltage to drain from capacitors and such) to give the engine a full reset. Wipe its memory to ensure it's not hanging on something. If you
can get a scanner, then you might not want to do this just yet until you connect the scanner, as it will clear codes that might be helpful in finding the problem.
good luck, and keep us posted.