T&T: Vacuum in fuelm lines

[Phil Little]

It is possible that the inner lining in a fuel hose is collapsing and restricting the flow. You might replace any rubber fuel hose if you have already done so.
   
  Phil Little

john brees <breeswood at hotmail.com> wrote:
  Greetings everyone,

I've been having an issue ever since I have owned Huckleberry and I would like
the groups opinion whether it is a problem or just an individual idiosyncracy
of my engine.

The engine is a Perkins 6.354 Range 4 M135, 1991 vintage, the last
modification before discontinuing the series. It runs well when it has clean
fuel without air bubbles but that was another issue. I had noticed that the
vacuum gauge would show 2.5 -3.00 -psi at normal operating speed and temp., it
would remain at that vacuum for 2-3 hrs or more then slowly creep up to 5,
then 6 over a period of several more hrs. The engine continues to run
normally. When it first occured, I switched Racors and changed filters, but
the with the new filter it would do the same thing. Also, when I ran the next
day with the same filter it would start out at 2-3 then creep up to 6-6.5

I concluded that my fuel was badly contaminated (the boat had laid idle for
about 2 years in Texas before I bought it ) and in fact there was a lot of
crud that started showing up in the filters as the fuel level became lower. I
had filled the tanks in Texas, about 700 gal total, and put about 200 hrs. in
the past year. I had about 250 gals in the tanks when the crud started showing
up. I also condidered that my vacuum gauge might be inaccurate.
I had a professional fuel polishing/tank cleaning outfit, PetroScrub, out of
Olympia WA come and open up my tanks, completely clean the tanks and polish
all the fuel with a 0.3 micron filter before returning the fuel to the tanks.
I also installed 2 new vacuum gauges on the Racors, the ones that replace the
T handles.

I thought that would solve my high vacuum problem;but, no, the same thing
occurred on three days cruising from Port Ludlow to Friday Harbor to Anacortes
back to Port Ludlow. I did not change filters when the vacuum rose because I
couldn't imagine that the fuel would have any more crud and visual inspection
of my filetr bowls looked clear. Each day the vacuum would be lower then rise
during the day and I assumed that if the filter was plugged that the vacuum
would remain the same.

I also thought that I may have an occluded air vent to the tanks. I had
previously checked the vents by flowing air from the shop vac exhaust through
the fill holes and got good air flow out the vents. Even so, opened the
fillcaps while underway and I heard no whooshing sound as if the tanks were
under vacuum. The gauge remained at -5.

What says the group? Do I have a problem? If so, what is causing it and what
should I do to correct it? I have followed similar theads and most report
vacuum gauge readings of 0 to -2 or -3 as normal.

John Brees

Huckleberry KK42

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