After you get the fuel system cleaned, try to move the throttle linkage on the injector pump up, I'm betting its not going to move. The plunger inside the pump always gets gummed up and if its at the lowest position when starting, it will break the plunger guide. Then you have to disassemble the pump to replace the guide. I always fill the last fuel filter canister with acetone or carb cleaner, then turn the fuel pumps on. As the fuel starts mixing with the acetone start rotating the engine over by hand while moving the throttle linkage up and down. You can also take the large nut off (in between the hard fuel lines), then remove the cap, spring, and other pieces to gain a view of the top of the plunger, then rotate the motor over by hand and see if the plunger moves in and out (if it moves in and out you're good). You can use a brass punch to hit the plunger if its stuck in the high position, to move it. Worse case, you may have to pull the pump off to clean it.