I've just completed a body swap on an E350 van with a 6.8L (you can see the whole project at https://www.ford-trucks.com/forums/1...on-a-99-a.html). I've got it all back together and it will barely run. It starts, and will barely idle, sputters, backfires and will barely rev.

My first thought was that I've missed hooking something back up. But, I've been through it several times and am confident there is nothing that I've missed.

It acts like a massive vacuum leak, but I've checked all of the vacuum lines, emissions hoses and connections, including the PCV hose and elbow under the throttle body. I've also sprayed carb cleaner on the intake and vacuum hoses and connections. I'm fairly confident it is not a vacuum leak.

While the body was off, I replaced all spark plugs with new motorcrafts. And I replaced all of the COP boots. I initially discounted the idea of it being a COP issue since the plugs and boots were new and the engine ran fine prior to the body swap. However, not having many other ideas of what to check, I started unplugging the COPs one by one...or rather one after another. I now have five COPs unplugged that have not affected how it runs. Any that did affect it, I plugged back in. Thinking that I somehow (maybe the power washing of the engine) damaged a bunch of the COPs, I started replacing the ones that were not working with spares from the other van. That has made no difference.

So, I have at least five (four of which are on the driver side) cylinders that are not firing. What would cause this? I'm wondering if a fuel issue has caused the ECM to shut down those cylinders.

Any ideas/help would be appreciated.

 

Hmmmm....111 views and not a single idea yet. Let me bump this along a bit. The current thought is that there is some difference between the engine wiring harnesses on the '97 vs the '99. If anyone has access to part numbers/manuals, could you please look up those respective part numbers to see if they are the same or different? The expectation is that they are different, slightly, and that I'll need to pull the '97 harness off of that engine and install it on the '99.

At this point I have only determined that unpugging some of the COPs doesn't affect how the engine runs. But, that doesn't mean that there is no spark...could be that there is no fuel to ignite. So, a bit more diagnostics will be required to confirm whether it is the COP that isn't firing, or the injector that isn't providing fuel. Need to confirm proper fuel pressure as well.

 

Hmmm...I really thought someone here would have access to part numbers or something to be able to determine if the harnesses were different or not. I guess not.

So, I started doing continuity testing to see if the COP wire's pin locations were the same on the two harnesses, and they were not. In fact, some of them were on different blocks!

So, that pretty much solves the mystery. The harnesses are indeed different. Also, they have different style plugs for the fuel injectors. The '99 has a black plug with a single black release tab, whereas the '97 has a grey plug that releases by squeezing both sides inward. Here's a couple of photos:


So, I've swapped the harnessses, and I had to swap out all of the injectors so that I was using the '97's injectors that would plug into that harness. Now the engine starts right up and purrs like a kitten! Problem solved.

BTW, the newer, black style injector plugs that are on the '99 (and presumably newer) are crap. EVERY one of the locking clips broke off as I was trying to unplug them. I think that the older, grey style plugs are a much better design.

 

Glad you figured it out. That is one thing that sucks about newer cars is that parts seem to be really reliant on year and model to where you cant change a lot of parts over unless the part numbers match.