I for about 2 years have been getting an intermittent low fuel pressure light on my ‘74 Spider. It would be fine when cold in the morning, but driving home at noon the light would flash. I believe the car has a light to protect you from running the Spica mechanical injection system dry which I would presume would damage it.
I diagnosed it through some intuition. I noted the rear electric fuel pump is silent when cold, but sounds gravely/rough when the light is on, I pinched off the discharge hose and noted no difference in sound. I pinched off the supply hose and it got worse. My theory, pump is starving and I am hearing cavitation or vapor from flashing fuel going through the pump. I turn on my air compressor and wrap a rag around the air chuck and put it in the tank, A quick hit of air and the pump quiets and the light shuts off, diagnosis confirmed
Since the tank was full, I squeezed off the line upstream of the filter and pulled the filter, I rapped the filted on the ground and you can see all the stuff that came out, I blew brake cleaner through it and got more of a fine gritty material. I re-installed the filter and it is good as new,
I’ll wrap this up with a mention of some of my favorite tools. First is my 20 year old or so track mat mechanics mat. It makes laying in the ground a lot more tolerable. One of my best presents ever. Also, I love my Showa gloves. Protects your hands and keeps them clean, Beat of all is they are so sensitive you can pull a dim out of your pocket with them on, They really are nice.