1993 Nissan Pickup D21 Won't Start!

I have this truck as a daily driver (130,000 miles, 2-wheel drive, KA24E, 2.4 L) and just recently on my way home from work the rocker arms or lifters, I couldn't tell which, started knocking extremely loud when I was in fifth. I made it home and took a look at the truck everything seemed to be in order. It had done this in the past for the previous owner a.k.a. my brother, but it seemed to be because the rockers were not getting enough oil and the oil pump was replaced. I went to the library to get the repair manual and on my way home I put it in second and went to give it gas and the engine bogged down like it wasn't getting enough fuel. It did this also in first which made driving on the main roads a hassle. I looked it over again at home and found nothing wrong. It was getting spark, fuel and air and on top of everything else there were no CHECK ENGINE lights on the dash. When I got to the fuel filter it was pretty dirty so I changed that out and checked fuel pressure and it seemed good. I gapped and cleaned the plugs and now I can't get the engine to start at all. I thought that it may be the O2 sensor but the O2 sensor only affects the E.C.U. during WARM or CLOSED LOOP operating conditions but it would not have any effect on the engine when starting from a COLD or OPEN LOOP operating condition. The next thing I will check is the camshaft position sensor I have heard that this sensor can cause some of the symptoms. If anyone else has had a similar problem please, by all means respond to this posting I really would like to know why this is happening. I am unsure of the relation between the rocker arm noise and the bogging down of the engine but I will keep at it!