hey guys i just picked up a 89 f-250 5.0L 4x4 project that somewhere down the road has had a "mustang" 5.0L swapped into it, the PO said he tried and tried and could never get it to run right (he did not do the swap himself, he bought it that way) when i got it from him, it was in shambles. i just finished plugging in the wiring harness for the EFI as well as the 40+ damn misc vacuum lines
i bought a new battery (everything gets power and seems to work as it should) i gave it a spits of starting fluid and she fired up and ran on like 4 cyl. honestly.. it sounds like some wires are backwards and/or the distributor is out. but what else would cause this? is it common for this swap to run poorly for any reason?

and what 2 firing orders could it possibly have? or is there only one for the truck and the mustang 302?

after i hear from you guys what the firing order is, i'm gonna re-stab the dizzy and double check the wires for my own security before moving any further.

thanks guys!

-Nate

 

Mustang 5.0 has the 13726548 firing order.

 

okay i redid everything and it still runs the same, it will idle and run but it is definitely not firing in cylinders #5 & #6. (every port on the manifolds is hot except for these two.

i did confirm that they are both getting spark, and have GOOD reason to believe they are getting fuel too (smells very rich/white smoke) i took the DS valve cover off to check the rocker arms/valve springs and it is all nice and tight.

why the hell else would this be happening???

thanks

-Nate

 

What computer is in it? Did the PO try to convert the truck to mass air and only get half way through the wiring or do something really stupid like plug a mustang computer into the truck harness? That won't work because these older truck are wired for batch fired injectors while the Stangs were sequential injection.

 

i don't know for SURE which computer is in it, he said it was the original truck computer (but who knows ) is there any way of telling?

it sucks because the damn thing acts like it wants to run but it is dragging those two pistons on its back

 

Before anything else, you need to do a compression test to make sure the engine is sound before chasing any other issues. All spark plugs out, check each cylinder with the throttle plate wide open. Let us know what numbers you find.

 

You will have to pull the computer to see what it is, should be a tag on the side of the connector with an alpha numeric code that we can decode. And while it's out you can buzz out the injector harness, injectors 1,4,5,8 go to pin 58 on the computer and 2,3,6,7 go to pin 59.