2000 rodeo 2.2 l will not start. Hellp

i have a 2000 isuzu rodeo an have had nothing but problems with it. i just replaced the starter, water pump, oil pump an it still will not start. i need any help i can get to fiqure this out please. it has new head gaskets an spark plugs also, it acts like it wants to turn over but doesnt. thanks michelle