what is the serial number of the unit? does it show any codes after cranking? are all the wires on the starter? by power on neg side do you mean battery volts? that don't sound correct to me.might want to check to be sure your wires are correct, also whats your oil leval like if oil pressure is to low at start up your unit wont start might want to check to see that there arnt any blown fuses and if this unit has the two large ones on top of valve cover check them as well make sure your oil pressure wire is connected if this unit has a sensor in the top of the radiator (rh side) check leval if its to low unit wont start or will start then shut down