I have a 1989 ford f150 300 straight 6 ,i got gas one day and drove home everything was fine i parked it and the next day it would turn over but wouldent start.I could turn the key and actavate the fuel pump 4 to 5 times and it would start and run for about 5 seconds.i changed the fuel filter and checked the plugs 3 out of the 6 were coverd with oil and smelled of gas i cleaned them and it started and had more power than before but would blow out white smoke. i let it idle and it went dead now it will crank but wont start again.what could the problem be?