In the Yamaha Service Manual it says to check fuel pressure within 5 seconds after start switch is turned on and that the pressure should be 50.8 psi. After 5 seconds the pressure should be 43.5 psi. Then after warming up the engine the pressure while running should be 50.8.
On my engine the pressure within 5 seconds is 100 psi. After 5 seconds the pressure drops down to zero. While running the pressure is upwards of 100 psi.
My questions. Should the pressure regulators be operating within 5 seconds to keep the pressure down to the 50.8 specified? Then how long should it hold the specified 43.5 psi before leaking down?
The manual also says to test the regulators by applying vacuum to the pressure regulators and that at the specified level fuel pressure reduces.
What is the "specified vacuum level"? I can't find it anywhere in the manual.
I apologize for the wordy post but hope that I got my point out there. This has been an incredibly frustrating couple of weeks...
Need to remove electric fuel pump from VST and check oring where pump fits into housing, probably broken or installed incorrectly. Once that is repaired it should hold pressure, then recheck fuel pressure.
Okay, I bought fuel regulators from you guys and installed them. Fuel Pressure now is just over 50 and holding when running at up to 1500 rpm. Motor still dogs out above that. Ran the diagnostic and it shows the fuel rail pressure at 1000 when started but drops down after running for a moment or two. Disconnecting the fuel hose from the mid filter canister just after the VST shows a good quantity of fuel coming out of that filter. What next?
Tried a different supply, no better. Lift pump pressure holds at 6 psi, electric pump pressure holds at 50. The restriction appears to be going into the fuel compressor. Is there some type of screen or filter at or just inside the high pressure pump?
HPDI Fuel Pressure Question
Linear Mode
