Z 250TXRB Hpdi Losing Fuel pressure

[jimmytanner]

I have a 2003 Z250TXRB HPDI . Losing fuel pressure at the top of VST. Idles at 50-55psi. (HP pump 979psi) over 3000rpm and med fuel pressure drops to nothing and HP drops to 20ish. Fires right up, Rough idle, rough idle also.

New water separator, new primer bulb, new Primary on engine, new LP pumps, VST filter cleaned.

The problem is obviously between the tank and the top of the VST.

If anyone is thinking electrical please explain in as much detail as possible the way to test.

About ready to set it on fire!

Engine Monitor
Monitor Item Result Unit
Engine speed 2250 r/min
Fuel pressure (7.0±1.5) 3.73 MPa
Fuel pressure (1015±217) 540.92 psi
Atmospheric pressure 1006.9 HPa
Atmospheric pressure 29.8 inHg
Ignition timing BTDC 16 deg
Battery voltage (12-16) 13.48 V
TPS voltage (0.5-4.5) 1.42 V
Throttle valve opening (0-90) 19.2 deg
Fuel injection duration 1.6 ms
Water temperature (below 90) 52.3 °C
Water temperature (below 194) 126.2 °F
Intake temperature (below 70) 39 °C
Intake temperature (below 158) 102.2 °F
Electric oil pump *****
Firing of cylinder #1 Yes
Firing of cylinder #2 Yes
Firing of cylinder #3 Yes
Firing of cylinder #4 Yes
Firing of cylinder #5 Yes
Firing of cylinder #6 Yes
Starter switch OFF
Engine stop lanyard switch OFF
Main switch ON
Shift position switch OFF
Water detection switch OFF
Oil level switch (remote tank) ON
Oil level switch1(engine tank) OFF
Oil level switch2(engine tank) ON
Oil level switch3(engine tank) OFF
Water temp switch (overheat) OFF
Dual engine system switch OFF
Shift cut-off switch OFF

Data Logger[Engine operating hours according to engine speed]
Engine speed Time[h]
- 1000 r/min 150.2
1000 - 2000 r/min 75.1
2000 - 3000 r/min 8.3
3000 - 4000 r/min 99.9
4000 - 5000 r/min 17.2
5000 - 6000 r/min 1
6000 - 7000 r/min 0
Total hours of operation 351

Data Logger[Data comparison graph]
Engine speed[r/min] Fuel pressure (7.0±1.5)[MPa] Battery voltage (12-16)[V] TPS voltage (0.5-4.5)[V] Water temperature (below 90)[°C]
650 6.71 13.04 0.74 55
550 6.71 12.45 0.61 57.5
550 6.66 12.38 0.61 56
1800 6.61 13.55 1.33 56.3
1300 6.61 13.55 1.07 52.3
600 6.56 13.04 0.61 53
600 6.51 12.89 0.61 56.3
550 6.46 12.74 0.61 55
650 6.61 13.11 0.61 55.5
950 6.56 13.62 0.94 53.5
1050 6.51 13.55 1 55
600 6.76 12.52 0.61 50.5
500 6.71 12.38 0.61 53
550 6.66 12.38 0.61 55
500 6.71 12.45 0.61 56.3
550 6.71 12.6 0.61 56.7
550 6.71 12.45 0.61 56.7
550 6.61 12.82 0.63 56
700 6.81 13.11 0.8 53
750 6.71 13.26 0.8 54
700 6.81 13.11 0.8 53
700 6.71 13.04 0.82 53
1100 6.81 13.55 1.02 53
950 6.56 13.55 0.94 52.7
950 6.71 13.55 0.94 52.7
1000 6.76 13.62 0.94 52.7
950 6.71 13.55 0.94 52.7
1350 6.76 13.55 1.09 52.7
2200 3.73 13.55 1.41 52.7

[rodbolt17]

I am thinking either the lift pumps are faulty,the VST filter is clogged or you simply cannot supply the lift pumps with fuel.
not thinking anything electrical.

[jimmytanner]

Ten four! replaced the VST filter and she is now up and running! I had cleaned it with carb cleaner, ether and compressed air. after installing the new one I cut the old one and obviously the cleaning didn't do.

However, It still is a bit on the rough side at idle. any ideas? would there be any improvement in idle if I changed the plug wires? it is likely they are the original. 351 hrs.

tachs out at only 5500 fully trimmed light loaded.

Thanks for your help!