My truck went back into the shop on Wednesday. The truck had a miss at cruising speed on the highway. When I got back to town, it was idling rough and would fall on it's face above about 2000 rpm.

So the tech diagnosed that return fuel pressure was leaking into the cylinders, and replaced the injector to head sealing washers. This is the second time in 3000 miles that these washers have been replaced. I drove the truck out of town this weekend and am still having the same problems.

Can someone explain how the injector to head sealing washers would prevent return fuel from leaking into the cylinders? This does not make sense to me, but I have never had one of these apart in my own hands. Any idea what else could be causing the return fuel pressure loss? The truck has about 21,000 miles on it now, and this will be about the 6th time back to the shop for these symptoms. The dealer seems to be going in circles on this issue.

 

The washer is a copper washer, if they are going bad on a regular basis the head probably needs to be replaced because the sealing surface is not flat enough for the washer to seal.

 

The injector has a copper sealing washer and an O ring further up the body above the high psi fuel feed passage. The return fuel is actually routed from the injector to a cavity in the cylinder head surrounding the injector from the copper washer near the tip, up to the O ring. It's important that these two points seal to A: keep the fuel in the return system and not let it bleed into the intake tract, or crankcase. B: to keep air from entering the return system which can result in long crank time.

Personally I would think if you had a sealing washer issue you would have a bit of a smoke show when you started the engine. I have not to date replaced those sealing washers or O rings for an "engine miss" issue.

 

Thanks for the replies, so it sound like bad washers could actually cause these problems but in this case, two sets of washers haven't fixed it. I suppose a bad head sealing surface is possible. I haven't had smoke at startup since the #1 injector was replaced about 7,000 miles ago.

Is there something else that could cause fuel return pressure to drop? I should also note that these problems are much worse when the engine is hot, like after driving 30 minutes on the highway.

 

Anyone have any other ideas? Dealer has had truck all week and they can't seem to figure this out.

 

Dealer finally called on Friday and said they have a new ECM on order.

 

Yeah - I'm sure that's gonna do it!

 

I dunno...I am getting discouraged with this truck. I really like it but I need it to run right. If this doesn't fix it, I am going to have to start talking about a buy back.

 

Well they finally got my truck done today. According to the tech the truck set a P0606 Internal ECM Processor code while he was driving it. So they put in the new ECM. He also said he noticed some fuel knock while he was test driving it after replacing the ECM and ended up replacing the #4 injector also.

Hopefully this is all over with and I can enjoy driving my truck again.