If you think it could be fuel pressure, this is what I did to check it. I replaced the Schrader valve at the fuel filter canister, with a 1/8 pipe thread nipple with a hose barbed end at the other end, from Home Depot, and slipped a hose about 6 ft long and a cheap mechanical fuel pressure gauge at the other end, clamped everything tight, and that way I can start the engine and see if the pressure comes up while cranking and upon starting. If you do that you can run the hose in the cabin through the window and drive it, or just let it idle until it stops while you watch the gauge.
Eventually, I am going to replace the Schrader valve with a nipple about two inches long, and use a female T fitting to leave the gauge on one side, and the Schrader valve on the other side permanently. Possibly later, Iíll run an electric fuel gauge into the cabin.