4 suppose to be 8
 

i have just rebuilt a 302 that i pulled out of a junk yard and swapped it into my truck, which is a 90 f150 302 and i am having a prob with a firing issue... can anyone tell me what to check out or do to see why i only have 1,4,6,7 firing and the rest seem to be dead. i pulled the plugs off all and seems the 2,3,5,8 arn't firing cause there is no change and dont die when there off. if anyone can tell or explain what i need to do from here would be great help. thanks

Are you sure you have the firing order right, are the 2,3,5,8 getting spark to the plug . You need spark , fuel , & compression for the cylinder to fire, i would start there....Lew

yes i checked the firing order it is a HO motor and have the wires ran right. htat was the first thing i checked. i do have spark to the sparkplugs. compression is there the only thing is to check i guess for is the operation of the injecters. maybe i dont know just seems odd that its not one bank out its staggerd around the motor. and being half of it also.

The injectors on that motor are batch fired and you could have a broken wire which would disable 4 injectors, the pairs are 1,4,5,8 and 2,3,6,7.

where do i start to check that out what am i looking for would it be in a haynes manual?

Maybe.. but if not pin 58 at the EEC connector is tied to 1,4,5,8 and pin 59 is on 2,3,6,7, test for continuity with a DMM between this pin and each of the injector connectors(with the computer and all injectors disconnected) and if it is open simply patch in a new piece of wire. Be sure to disconnect the battery before doing any of this.

Are you sure it's an HO motor? I thought the trucks didn't get the HO until 1992 or 1994?

The trucks didn't get a HO at all.. only mustangs. The truck motors did get a new roller cam in 1994 but that still doesn't make them a HO.

positive its a HO motor the firing order for the 351 works and the firing order for the 302 doesnt so i would have to say it is. i will have to check the pins and see keep you updated

The roller 302 truck motors uses the 351 firing order to , the main difference in the HO is the cam & pistons , up till 93 the HO had forged pistons , 93 & after hyper pistons ....Lew

BTW make sure your distributor has a steel gear on it . The roller cams are steel...Not sure what dist you used ....

it is the original distrb and it is a hydro roll cam

i also replaced the wires cap and rotor when i droped the motor in