High or Low FP ? with YDS results

[orionn72]

Working on buddies 2001 Z200TXRZ
He lost RPM's and limped it home since then this what we did so far:
sent injectors to the injector man for service
replaced the MYSTERY filters
cleaned O2 sensor
cleaned VST and found no screen on pump filter (not sure if it was removed by previous owners or mysteriously disappeared)
replaced canister
replaced water/ fuel separator

engine will run for only a few seconds before dying
connected the YDS and Engine Monitor results:
all sensors - Normal
Fuel Pressure (5.0+-0.8) 1.2 MPa
Fuel Pressure (725+-116) 174.29 PSI

My question is what fuel pump is measured by the YDS? Could this issue be from the High or Low or BOTH FPumps.

Thanks for any input...

[boscoe99]

YDIS provides the HP pump output pressure.

A regular fuel pressure gauge is used to measure the VST pump output pressure.

Are you monitoring VST pump and HP pump pressure as the motor dies? If so, what do you see?

[orionn72]

Have not used a pressure gauge to measure VST.

Motor turns over then dies.

We tried pumping the bulb when starting - bulb stays hard with no help in starting/running.

Before my buddie shells out big bucks to replace the HP pump are there any other ways to test the pump besides the YDS reading?

Thanks

[rodbolt17]

what YDS is telling you is there is simply not enough fuel pressure on the HP rail to run.
nothing more nothing less.
that's all folks.
from there its up to the technician to figure out is it lack of pressure on the medium pressure side ,a restriction between the VST and the HP or the actual HP.
there are NO mystery filters.
there is a filter mounted before the lift pumps.
a filter on the VST pump, a filter between the VST and the HP, two filters in the HP and one filter in each injector.
no mystery here.
if the 50 psi medium pressure system is working and the HP filters are clean the engine will run on just the 50 psi side.

[boscoe99]

Don't buy a replacement pump if the one in question is defective. It can be rebuilt. Or, serviced with just the "not so mysterious" filters being replaced, if they are what is causing the problem.

I have read of one guy plumbing a 1500psi gauge to the pump output to measure HP pump pressure. Yam suggests using YDIS.

Fuel pressure gauges for measuring VST pump pressure can be found at most any auto parts place.

[orionn72]

Update:

Hooked up an external tank and fuel pressure gauge to the VST and got the following results:

48-50 psi at shredder valve : good

Connected the YDS and had an increase in results without an increase in performance (did run a few extra seconds before dying)


main fuel system / external Tank
Fuel Pressure (5.0+-.08) 1.2 MPa / 2.77
Fuel Pressure (725+-116) 174.29 / 401.88

At this point I am guessing it is the HP FP failing

All filters have been replaced including the canister and the small HP filters...

[rodbolt17]

I send my pumps to Flagship Marine in Punta Gorda FL.
contact Jeff there for shipping instructions.

[orionn72]

Thanks Rodbolt..

I cannot find any info on their website about $ for yamaha HPFP service ,do you have a ballpark price ?

[Cobia270]

I had my pump serviced by them 2 years ago and it was roughly $500. That was their charge just to service the pump.