I'm looking for anybody that has ever had this happen or might have the solution.


About a year and a half ago I had a local shop rebuild a 351 for my 89 Ford F-250. Because I was sitting behind a desk dispatching at the time, I paid a friend likes playing mechanic to put the motor in. Out the door it didn't seam it ran right but was going down the road ok so I just went with it. Then the truck ended up getting parked because I was still sitting behind a desk and didn't have much time to mess with it. So at the beginning of the winter I started driving it more, and have put close to 2,000 miles on it when I noticed it was definitely missing.


So about 2 months ago now (I'm guessing) I start looking it over. First thing I noticed is that the firing order was wrong. The idiot had it ordered and timed to a 302 (15426378) instead of the correct order of 1-3-7-2-6-5-4-8. Once I straightened that out and restabbed the distributor a couple of times to get it in the right spot and set the timing I was still noticing a miss. Actually 2. Cylinders 4 & 5.


To this point I've checked everything, vacuum is 15 inches and steady, fuel pressure is steady at 35 psi and jumps up to 40-45 when the vacuum line is removed from the regulator, compression on the cylinders runs pretty consistant in the 180-200. Only cylinder that seams low was #6 with a readying of 175 and then 165.


I've replaced with new the plugs, plug wires, complete distributor, new coil, I've checked the wiring harness from all ends, replaced the ecm with a new one. The fuel injection wiring harness doesn't look great but I'm not getting any indication of their being a broken wire. I can hear the injectors clicking and can smell fuel. I replaced the injectors anyway with rebuilt ones and blew out the fuel rail with air to make sure there wasn't a clog or something. There have been no key on engine off codes til today when I got a code 95 indicating Fuel pump secondary circuit failure. Only code I get when I do a KOER test is 42 indicating No HEGO switching detected always lean (right side).


I did figure out that my rear in tank pump is dead but my front in tank pump is good and I can hear my high pressure frame rail pump working. Fuel pressure also maintains for at least a minute after the key is off.


What am I missing? Its always 4 & 5. The misses don't change even if I swap the plugs and wires. I even pulled the intake manifold up and put new gaskets in and resealed it thinking that might have been the problem based on the cylinders locations. Anybody have any ideas that I've missed?


Thomas

 

Have you checked spark on those 2 cylinders?

Your compression readings seem exceptionality high. Did you perform the test with the throttle body plates closed or open?

Another idea is a leak down test. Perhaps the rings weren't staggered and all 3 rings gaps are the same allowing for compression lost.