6.0L air in fuel, runs rough at cruising speed.
 

I have Excursion with 6.0L that I cannot figure out where the air is coming from in the fuel.

Started out with a no start condition, replaced HPOP, IPR, and icp sensor. Started fine after this. However it has a miss while cruising 60-70 mph. i can also feel the miss when running the engine rpm up while parked, it starts missing at 1700 rpm to 2300 rpm.

I have found the fuel is aerated from the Fuel pump on the frame rail which is a new pump. Also replaced the pressure spring in the upper fuel filter housing. I removed the fuel tank and checked the pickup tube and checked the lines with vacuum.

The question i have now is, can an injector oring/copper washer failure cause the fuel pump to draw air into the fuel system from return line via the filter housing while the engine is off?

The copper Oring won't let air bleed in when it is off but it can let combustion pressure right into the fuel "rail" that is machined into the head causing the problems.

Thank you for the response bobfbigman,

I re-tested the copper washers just now by removing filter, topped off filter housing with fuel to cover the stem and cranked engine with remote starter, no bubbles. This after the engine was at operating temp. However when I cycle the key to run the frame rail pump I get aerated fuel in the bowl.

I guess I will figure out how to test the return line from the filter housing to the pump return inlet. Its the only one I have not vacuum tested.

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Collected some AE data for diagnosing 6.0L miss between 1700 rpm and 2500.
Would like to hear some opinions on what you think.


KOEO - icp -31.72psi IPR - 14.84% FICM 48

Idle - Icp - 635psi IPR - 23.05% FICM - 48

2500rpm - Icp - 1380psi IPR - 47% FICM - 48

My truck had little bubbles in fuell in bowl . . I think it's actually normal. I switched to an airdog2 since I had 175000 miles on stock pump anyway. You may have a stiction issue with an injector. Can you get a scanner that will graph your injector pulses?

I have an AE and the Balance test does not indicate any particular cylinders being bad. the graph will vary up and down slightly.

I would run some good cleaner/ cetane booster like power service and see if you notice a difference. Also what are you running for oil? As injectors age they get dirty and worn. . .anything to prolong their life has to be good for the wallet. . .i just tried 2stroke outboard oil in fuel for a little lube. It's made to be burned and a little bit seems to make it a little smoother. . .im no expert, just looking for longest possible fun time between repairs. :tu:

Great this helped me as we'll thanks

I sent the injectors on the driver side out to be bench tested, 3 good, 1 failed. They said that the nature of the failure would have caused a cold start miss. Passenger side had 3 brand new Ford reman injectors...so I guess I will go ahead and pull the one injector on that side and have it bench tested as well. Maybe, just maybe its the one causing the miss.

FYI on the 4 injectors I pulled the orings were perfect and the copper washers showed no sign of any combustion gases leaking by.

Thanks for the ideas, much appreciated.

Got the injectors back. One was repaired for a faulty solenoid that would have been a cold start issue. Installed them and test drove...SAME OLD SAME!. Still missing between 1700 to 2300 rpm.

If anybody has got any ideas I would appreciate it.

UPDATE: Took this truck into Ford to have them run a diagnostic test. They came up with Injector 5 and 7 low. 5 was already changed with a Ford re-man unit. I replaced both #5 and #7. Still same problem.

Today I ohm tested the injector wiring harness from injector to FICM plugs all good. no chaffing that I could find. Ohm tested each injector coil, cold and warm. All measured from .6 to .8 ohms. Pressure tested the HPOP again, no leaks. Rechecked fuel pressure, 60psi minimum at WOT. Swapped out FICM with another unit that is known good. There is a gurgling noise from the oil filter stand pipe when I pressurized the oil system with air. This is probably air leaking back through the HP pump. I don't know what to check from here.

Are there any known problems with PCM??

Still looking for a little advice or comment that may cause a break thru on this little gem.