my friends rb25det swapped s13 has been running good since the swap was completed 3 weeks ago, yesturday he drove it home from work and parked it then tried to start it today and all it will do is start and act like it is going to run but immediately just shuts off then it will just turn over, if you let it sit it will do it again and act like it is going to start but then shut off. we have swapped ECUs, checked the fuel pump made sure it was getting gas, checked connectors, checked for vacum leaks. I dont know what to do we are stump and need some help anything would be appreciated