i have a 1970 280 sel,the injector pump is not pumping fuel into injector lines.the cold start solenoid is not hooked up ,i don't know which wires go to it.fuel pump is working,fuel filter is clean,fuel is going into pump,no fuel coming back out to return line.all the pistons seem to work fine.the push rod goes in but returns very slow.with the 6 injector lines disconnected and i turn the motor over no fuel comes out.if i need to rebuild the pump i am unable to find anyplace to do it.i have called several m/b shops and they dont know where i can go.thanks,robert martin