We checked the code said number 1 injector was bad so we replaced it and no dice. Replace plugs and wires still nothing. Pulled oil filler cap everything i can see is moving. Compression in number 4 was only at 40psi! He just bought the jeep three days ago and seller said it had a rebuild 1000 miles ago and no problems with it... All the gaskets up top and below apear to be new. Does anyone have any ideas?