f150 problem after fuel filter change

[lakelife]

F150 was running high end fine but searching for Idle at dock fluctuated 500-900. Changed separator and on board filter and all hell broke loose. Started chugging at higher rpm's and breaking down like a bad coil symptom. Idle not fixed.

IAC valve was very hot and failed testing- replaced and got back the smooth idle. Water tested still breaking down around 4000.

Cleaned VST, injectors and tested fuel pump pressure(40lbs).

Water tested and it ran very well for about 1mile or so then started acting up again not going above 4300 and only if I feather the control at top rpm's.

Still idles well.

Hooked up computer and ran under load no obvious issues and no codes past or present.

Feels like fuel issue now. Injectors clogged again from loosening debris when cleaning etc?

Motor is 2004 with only 300 hrs.

[99yam40]

did you monitor the fuel pressure when problem shows up to make sure the pressure is not dropping?

air leak at filter might cause the VST to run low of fuel on high RPMs

[TownsendsFJR1300]

Did you change out the Yamaha, under cowl fuel filter (right in front of the balancer)?

If so, that cup swells and the black seal will NOT seat FULLY when re-installing. The large black nut will feel tight but un-less that cup IS FULLY IN, you'll suck air.

If you squeeze the primer bulb hard, you may get fuel leakage when the cup meets the mount. Freeze the cup for about 30 minutes, then work quickly.

Or replace the cup for $10.00-They expand over time, ever so slightly & turning yellow...


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[pstephens46]

Have you been using Marine non ethanol or ethanol?

I would guess fuel issues as apparently it has been stored for long periods.

I know you just changed the boat mounted separator but wonder if it has water or contaminates from the short period you have run the motor. I would dump it in a glass jar to check. If so, you need to clean tank.

[lakelife]

99yam I have not checked under way. Just cleaned injectors again and synced intake pressure. Runs well on trailer- water test today.

Townsends- I did have issue initially with filter cup. Figured out thanks to this forum. fuel underway seems to fill bowl correctly.

Pstephens- not sure what was run in it before me I also feel from reading it may be fuel residue that may have moved when I have disturbed the old fuel separator etc. Not sure how to approach cleaning the tank. Just drain it as clean as possible or is there a cleaning method?

Thanks!

[TownsendsFJR1300]

That filter bowl will STILL FILL, even if NOT SEATED. You should be able to feel all the way around the edge, that it is indeed fully seated.

Couple years ago, after replacing the filter, THAT bowl was NOT fully seated. It ran for at least 6 months before it started acting up and stalled... Squeezing the primer bulb hard, forced fuel out of that area where I felt it.

[lakelife]

Back up and running!

After cleaning the injectors again and before the water test I did the ball pressure test and the on board filter (new bowl) held pressure with no leaking. seated well.

drained down tank and filled with fresh fuel, nothing obvious in old fuel but wanted to start fresh.

Water test went awesome- runs better than ever!

Thanks to you all who contribute to this forum!