im not familiar with the regina system . with the 240 and 740's I have they have the pere pump. If the fuel is lower than about half and the pre pump fails it can cause problems that go away with a full tank. dead main pump , car wont start.

you can check it , pull the fuel line off the fuel rail , into a jar. pull the fuse I think it was fuse 11 but check your book.. the idea is the pre pump will pump fuel into the jar and so will the pre pump but the main pump is way more powerful. by pulling the fuse you can tell which is running , you can hear it through the gas cap too.

I'd see if you have adequate fuel flow but be careful of starting fires with gas.

I was just fighting some issues that led to a bad fuel injector, once I pulled off the fuel rail and connected the ground wires back up and tried starting with the coil unplugged I could see the injectors spray but one was stuck and it was continuing to run fuel into cylinder 3 until the fuel rail was out of pressure. that caused a huge amount of fuel to collect in cylinder 3 and upon startup it was basically running on 3cylinders with one flooded until it coughed up enough gas to fire up in that cylinder.

after all that I'd look at that sooner in my troubleshooting sequence. there is a leakdown test you can prerform with a fuel gauge connected. that's more the "correct way" basically the fuel rail should maintain it's pressure not leak the gas into the engine upon shutdown. if you can connect a fuel pressure guage that's probably better and a way a mechanic would approach it but you can check those things with out it.

careful if you pull the fuel rail open and then turn the key, It'll pump a LOT of fuel out quite quickly , if you wanted you could pump it into a gas can and get an estimate of the flow rate.

with having the regina system I could be feeding you info that is inappropriate. I'm not sure what the differences are exactly and it is a different animal.

the relay for the fuel pump caries quite a large amperage and every time it shuts off it makes a spark across those contacts. over time the contacts get blackened. you can likely clean them in a pinch, but best to refresh that relay. I made myself a jumper with a fuse that will run the pump if it is installed.

if the car is ever in a crash you dont wan't it to e pumping fuel after the engine stops so there may be some protection to shut off the fuel if the engine stops. I think in my 240 there is a black relay on the inner strut tower on the passenger side but I could be confusing my 740 , they are very similar. If that relay is pulled the engine will immediately quit as it will shut down the ignition system. with Regina , I dont know probably they have something similar in there.

I don't think it fails as often as the fuel pump relay, maybe because it isn't conducting much amps like the fuel pump one. less amps means the contacts fare better.

I had a no start issue from a bad coil wire, the prmary winding, one was corroded. there may be an engine fuse in around the left inner fender area near the coil. Ive seen the plug for the AMm go green even though it has a boot , I found a bad conection cause me grief there before.

on my car there is a transistor on the inner fender near the airbox , it can fail. I mounted a spare in my 240 so I can just swap the wires over if I suspect it failed. regina may be different. I think it basically amplifies the signal from the ICU to deliver a larger amperage to the coil. Ive never had one fail but evidently they can.

dont forget the obvious, make sure you dont have a loose battery post connection, sometimes it is that simple.