HPDI 175 problems

[Onefishaway]

Hello, first off thanks for me allowing to join your forum. I have a 05 HPDI 175 that's giving me trouble. Last few times I took it out I noticed a lower than usual idle. Got to the ramp last week, motor started just fine like it always has. After attempting to get on plane the motor dies like it ran out of fuel. I brought it back home and replaced ALL the filters, screens and spark plugs. Problem still persists. I removed the low pressure pumps and ordered new ones. Diaphragms weren't cracked so I'm sure that's not a problem. It's gonna have to go to the dealer after this. Anyone have any ideas? Thanks in advance.

[boscoe99]

"first off thanks for me allowing to join your forum."

We did not have a choice.

Welcome.

If and when new pumps are installed, if it still does the same try and have someone pump the primer ball while you are trying to accelerate the motor.

Was the filter within the VST changed? How about the two filters that are within the HP pump?

Do you know anyone with the Yamaha diagnostic system? It can be used to get HP pump output. I presume that the belt that is driving the HP pump is in good condition. The motor will idle and run at low RPM on just VST pump pressure. It needs to the HP pump to be working well to obtain full power.

Of course there can also be injector issues.

[Onefishaway]

Yes all the filters were changed including the screen filters in the HP pump and the injectors. Belt appears to be in good shape.

[99yam40]

as Boscoe related to,
you need to know what the rail pressure is doing.
HPDI uses very high pressures, so lap top would be best to look at it with because not many gauges will be able to read that high.

I believe rodbolt said in the past you can measure voltage with a meter on the sensor and calculate pressure

[Onefishaway]

So here's another interesting piece of the puzzle. Took back to the lake to retest. Got essentially the same results however I noted that it would start and run pretty well in the trimmed up position. Lower the motor and it would run out of fuel and die. Pumping the bulb did nothing to change performance.