I'd love to know how the rumor got started that the lowest point in the fuel rail is somehow holding air.

 

I'm with you on this one. If I have all of this straight, many people are under the impression #8 has issues with air in fuel because the air reaches it - being the last on a dead-head.

What I believe I've learned: The firing order finishes up with #6 then #8 (right next to each other). #6 snorts up the goods out of the trough, the fuel pressure has a dip - and 8 gets table scraps. If there is too much air in the fuel line leading to the pump, you get cavitation, as well as other issues that diminish fuel flow. The 6-8 combination is the only pair of cylinders in the firing order right next to each other. As for the air... #2 and #7 would get first shot at inhaling that - but #1 and #2 are the highest point on the fuel rail. Flip a coin on #1, but #2 is going to be your problem child with air.

Everybody looks at #8 (and sometimes #3) because OBDII code readers and scan tools tell them to. The original Cam Position Sensor was a black one, and it did a beautiful job of sensing the timing wheel "doors" (window is nothing to sense, door is metal in close proximity to the sensor, triggering a pulse). Ford had to change the sensor for more reliability, but the new part sucks at reading the smallest doors on the timing wheel. I will allocate exactly one guess as to which two doors are the smallest, and a clever person can even figure out which one door is smaller than the other small one.

So you have a changed sensor, but the electronics that used the original sensor signal are still in place. The electronics/firmware were not designed for the new sensor, so it just tries to sort it out as best it can - dishing out #3 and #8 fail codes and/or high PERDELs. We are left assuming the code reader is gospel, but I know from experience computers can lie - if they are unwittingly programmed to do so.

"It says right here I have a bad #3 and a bad #8, so I'll spend my hard-earned money on whatever it tells me to." Question everything.

 

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