im installing my rebuilt injection pump and im having trouble getting the gear back on the shaft there isnt enough threads to get the nut on it. and i was told to pre lube the pump does that just mean to put diesel in it or what

 

You have to have the slot in the gear aligned with the key on the pump shaft. Make sure the shaft is unlocked. Some shops lock the pump shaft after rebuilding the pump. You can't install it out of time. It will only go on one way. The gear is keyed, and the shaft is keyed. Turn the engine over til the keyway in the gear is about 1-2 o clock position. More than likely the shop set your put to cylinder number one is straight down. Make sure the shaft is unlocked, then turn the shaft over to the 1-2 o clock position so that it aligns with the pump gear. You can thread the nut on the shaft, then with a big set of pliers turn it over.

 

Also make sure the woodruf key didn't rock back in the slot and is blocking the gear from going all the way on.

 

This is a common problem.. do as the other have said.. rotate it to the top.. get a good mirror... If the key is not very tight in the shaft.. I take the key out, and lay it on one side and put a dimple in one side with a center punch.. this will little distortion will keep it tight in the shaft when you install it..
Just don't drop the key inside the front cover... Just take your time... You'll get it..
Bryan