Musings on Yamaha stuff for Rodbolt

[boscoe99]

There have been several posts here and on other websites recently that appear to be about fuel flow (or the lack there of) from the lift pump to the VST pump on F200/F225/F250 models. The pressure relief valve between the outlet of the lift pump and the inlet of the lift pump seems to be the problem in a number of cases. Presumption is that it opens too soon, or has failed open, which prevents adequate fuel flow to the VST.

Any way, I got to thinking about other things that might cause insufficient fuel flow to the VST. Maybe a pump is getting weak and is not up to snuff. Maybe the pump is getting insufficient voltage to run it at a speed that will flow sufficient fuel. Maybe the F filter is getting clogged. Maybe a hose is failing internally. And maybe the pressure relief valve is failing open.

Anyway, have you ever thought of a fuel pump flow performance test? For instance, the pump must be able to provide nominally 25 gallons per hour to support an F250 that is running at WOT. Would there be any value in letting the pump send fuel to a clean container while measuring the flow of fuel over a period of time to see that all is copacetic? (Engine off, fuel pump powered by a battery with the hose that normally connects to the VST being placed in a container) Yamaha offers a similar test for an oil pump but makes no mention of testing the fuel pump in a similar fashion.

Just wondering if this would be a test to help someone pin down a particular problem.

Thoughts from and and all are appreciated.

[rodbolt17]

that pump should be able to flow about 105 LPH at less than 6"HG.
its the same pump the Yamaha fuel system test kit comes with.
I typically use a long return hose and place the fuel back in the tank.

that relief valve failure ONLY shows up below 1200 RPM.

[boscoe99]

that pump should be able to flow about 105 LPH at less than 6"HG.
its the same pump the Yamaha fuel system test kit comes with.
I typically use a long return hose and place the fuel back in the tank.

that relief valve failure ONLY shows up below 1200 RPM.

If it fails completely open above 1200 RPM is the thinking that the pump (in good working condition of course) is capable of both bypassing fuel and supplying fuel to the VST at the same time? I can see this happening if the flow path within the relief valve is small. Which I believe that it is.

Just trying to think of some simple tests that users can try without needing some expensive test equipment. Like the gizmo that Yamaha recommends which uses an FMM, a valve, and vacuum transducer I believe.

[zenoahphobic]

A hose with a tap preceded by a pressure gauge. Tap is adjusted to create backpressure (resistance) as specified and then the volume pumped over significant time (say 1 hr) is measured to see if meets horsepower flow rate requirement add margin say 50% (?).

To put pump into simulated workload and over some running time.