mystery starting/fuel issues
So I recently pulled the engine out of a '87 Platinum that had been largely neglected by a previous owner but was running well. I cleaned it and swapped many parts (mounts, belts, plugs, water pump, lines and hoses, etc...). Upon reassembly it started very briefly, and has only occasionally started for a few seconds since. I am at my wit's end trying to figure out what I got slightly wrong on reassembly!
I feel it must be something very minor and silly as the car can start occasionally and sounds healthy until it sputters to death. This indicates to me all the major stuff is right, and leads me to believe that there is most likely a fuel issue.
Most times I have tested it, moving the AFM flap causes the fuel pump to activate, but friday and this morning it didn't. I wanted to confirm the fuel pump was still good, so this morning I jumped 12V to the fuel pump directly and it ran fine. After this, the car started and ran for ~5 seconds, its longest run since the engine out work. It seemed that the car was functioning perfectly except for the fuel pump and died when the fuel in the rail was exhausted.
After some more electrical checks and parts swapping I have the pump working as expected again, but the car won't start. The cold start injector seems stuck open though, as when I ran the fuel pump fuel poured out the intake hose.
My guess had been that I have a situation where I either get the injectors to fire or the fuel pump to run but not both. Since I don't know how this is possible and the CS injector runs whenever the fuel rail is pressurized, I now think I may have a bad ground situation that keeps all injectors open at all times, but I'm not sure how to further diagnose as the grounds I know of seem secure and I have misplaced my multimeter (I'm borrowing one for my next stab at this!). Any pointers would be much appreciated to get me back on the road!
I can provide pictures or photos if needed, let me know what you need to see!