HELP

I have a 93 freightliner with an n-14 engine. I am sitting at a rest stop now and desperatly need help. The truck was running fine until this evening. Now it stalls whenever I come to a stop and attampt to take off. I have to wait for about 1/2 hour then it will start and take off ok. It will run down the road fine until I have to stop again be it 5 minutes or 2 hours. When I stop it will idle but as soon as I give it some fuel it dies. Whats going on?

 

Additional info. I had a shop replace a leaking gasket on the fuel pump about 2 weeks ago. Is it possible that could be causing this problem. Also I checked the codes, nothing showing.

 

More info. Checked and topped off coolant level. I am now going to clean battery terminals.

 

Fuel filter was replaced 2 weeks ago. Just checked codes again after cleaning battery cables and I am getting code 121 engine position sensor circuit. What is that?

 

more info. When I pull the codes I get 222. I know what that is and have had it for 6 months with no effect on the running. Now when the engine stalls and I try to restart it the check engine light flashes 121 code. But then when I pull the codes again it just gives me the 222. I'm lost.