F225TXRD "VST filter" and Command Link fuel flow

[fairdeal]

I was away from home for about six weeks - so the boat sat unused.
got back and ran it a few days ago.

started fine, ran great for about 10 miles and then - whoosh -
lost power, and wouldn't get above 3,000 rpms.

played around with the primer bulb,
determined that the VST was not running low
so figured the problem was the HP pump screen.

but I could still *****, so I did that for a few hours.

On the way home, I was able to make ~3800 rpms and keep the boat on plane
I noted that the NMEA display was showing atrocious fuel economy:



,
So at 2,126 engine hours, I opened up the VST:
(Had not been done since October 2014 @ 1050 hours)




Today its back together, boat back in the water, running great
and the MPG is showing normally:




So - point of the story.

as I see it:

- the clogged HP pump screen was reducing rail pressure

- the ECM increased the injector "on" time to obtain rpms

and then the ECM via CL/NMEA 2000 output reported an "assumed" fuel flow

which was actually incorrect.

[walleye1]

You sir are good.

[boscoe99]

Where is the sensor that measures fuel rail pressure?

If the VST filter, being somewhat clogged, reduces fuel rail pressure why didn't the pressure regulator make an adjustment to keep rail pressure within specifications? Or, was the regulator at the end of its limits and unable to make any further pressure corrections?

[fairdeal]

Where is the sensor that measures fuel rail pressure?

ha. that is one of my "always on the back burner" projects;

I bought a "generic" 3-wire, 5-volt-reference fuel pressure sensor from Amazon (only $15.00 IIRC !)

and have tested it with the engine's CL "speed'' input (pitot pressure)

I can display the NMEA 2000 on my Garmin as "water speed" -
but of course have to then do a "mental conversion" to psi

now dragging my feet on actually plumbing it in to the fuel rail Schrader....

was the regulator at the end of its limits and unable to make any further pressure corrections?

that is my assumption;

[HMBJack]

Good diagnosis and outcome Fairdeal…

Question - Is the HP Pump screen normally accessible and serviced as part of a VST cleaning?

If so, I suppose another point of the story is to simply have the VST cleaned every 750 - 1,000 hours. Yes?

And if not, I guess it's wise to have the HP screen cleaned at the same time as the VST. And maybe clean the fuel injectors while you're at it. Yes?

[fairdeal]

Is the HP Pump screen normally accessible and serviced as part of a VST cleaning?

If so, I suppose another point of the story is to simply have the VST cleaned every 750 - 1,000 hours. Yes?

And if not, I guess it's wise to have the HP screen cleaned at the same time as the VST. And maybe clean the fuel injectors while you're at it.

well, "cleaning/changing the HP pump filter/screen" and "VST cleaning" are pretty much the same thing
(plus brushing/blowing any remaining debris from the tank)

I agree about the injectors - which is why I just sent my "spare set" out to be tested/serviced
when they come back I will swap them in

(I recognize that a sensible person would keep a "spare set" in already cleaned condition - not "used & unknown")

[rodbolt17]

bogus test, bogus assumptions.
YDIS has had the capeability to display fuel rail pressures for at least 5 years.
the transducer can be added.
injector on time is determined mainly by MAP and TPS.
lose pressure and your going to increase on time via TPS and map.
MPG is a teat on a boar hog. to many variables.
GPH is what I want to see.

[boscoe99]

bogus test, bogus assumptions.
YDIS has had the capeability to display fuel rail pressures for at least 5 years.
the transducer can be added.
injector on time is determined mainly by MAP and TPS.
lose pressure and your going to increase on time via TPS and map.
MPG is a teat on a boar hog. to many variables.
GPH is what I want to see.

Are you referring to losing fuel pressure?

[rodbolt17]

what is the first thing that happens when rail pressure drops?
the operator pushes the throttle adding air and throttle angle.
the ECU responds by increasing on time.
rail pressure now drops even further.
operator nails it.
I have witnessed it to many times.

[boscoe99]

Got it.

Too bad fuel system output pressure is not monitored. Of course if it was then there is one more system to fail.

[rodbolt17]

why it is not monitored is beyond me, oil pressure gets monitored.

[fairdeal]

YDIS 2.0 is very nice I’m sure
but I cannot buy it
and would not spend that much anyway

given similar speed, load, sea and wind conditions MPG is a direct indicator of and valid comparison of what the ECM map says is the engine fuel flow

[boscoe99]

When I had my F200 I monitored the vacuum (hate that word) reading from the Racor fuel filter outlet port, using a Cyberdyne vacuum/boost gauge.

As well as monitoring fuel flow from a Floscan system.

I would have probably have added fuel pressure monitoring on the fuel pressure rail had I kept the boat and motor.

There is no such thing as too much information. Fun to watch gauges. IMO.

I shoulda been a flight engineer in the good ole days when there were such.

[rodbolt17]

similar aint enough.
tides,crosscurrents,winds hull condition all play a role. as the hull slows down it displaces more water thus taking more fuel.actually we are running 2.33 now.
MPG and MPH are rather worthless on a water craft.
couple extra coolers can make a difference in MPH and MPG.