2000 200HP HPDI issues

[NAESB811]

I have twin 200HP HPDI ( i believe Z200TRLY). The starboard runs fine, the port is acting up. Both run off the same fuel tank.

I was topping out at 4200 RPMs on the port (should be 5200 or so). Over about 20 hours, the 4200 top dropped to 3200 and eventually to 1500.

I though at first it was the VST. Replaced that no luck. I checked the electrical, there was some corroding on the connectors, so i cleaned those up. Getting 12.45 V at the posts. twinned the port to the starboard battery feed to test.

I pulled the spark plug wires one by one at idle to confirm that were working. I switched fuel lines on the motors. I ran an new fuel line from the water separator into the motor (also hooked to the starboard separator to test). I replaced the water separator as well. none made a difference.

put everything back to normal, I then replaced all the spark plugs (NGK (4952) BKR7ES-11) back up to 4200 for a while then the plugs fouled, rather quickly (2 hours). back to 3300 RPM.

I replaced all of the plugs again, back to 4200 RPM, but now if I rev the motor in neutral, it boggs down at 1500.

I am now baffled by why the plugs could possibly foul that quickly and why it wont rev in neutral. I don't think it is the fuel or oil since the other motor runs fine.

Any ideas of what to check next would be greatly appreciated. Summer in the northeast is very short.

Thanks for any help.

[99yam40]

=

I pulled the spark plug wires one by one at idle to confirm that were working. none made a difference.


I replaced all of the plugs again, back to 4200 RPM, but now if I rev the motor in neutral, it boggs down at 1500.

Some cylinders do not fire at idle, and more shut off when revving in neutral, so you need to find out how this motor runs before playing with it like this

[NAESB811]

the starboard motor revs right up in neutral, the port bogs down at 1500 RPMs. why would the engine speed, in neutral with no load, be affected by the # of cylinders?

While i do not know a ton about these motors, I am learning more and more everyday. This forum has been helpful with that.

I have one motor that seams to be running fine right next to the poorly operating one. I try to verify "proper operation" by testing what i do on the port on the starboard.

Rev the starbord in neutral, i can push it as high as i want, I rev the port, bogs at 1500.

I put the port in gear, revs to 4200 (for now until the plugs foul).

Thanks for the input, I appreciate any help.

[greasyshaft]

When in neutral both 2 & 3 cylinder shut off, above 1500 rpm(or 1200, can't remember) four cylinders are shut off #2,#3,#5,#6

You will need to measure the fuel pressure at both the medium pressure side and high pressure side.

High pressure side can only be measured through YDS.
Medium pressure via the schrader valve on top of the VST.

If the high pressure side drops and the medium pressure does not - problem is after the medium pressure pump.
If both pressures drop you most likely have a problem before the medium pressure pump.
YDS will also show you what cylinders are activated, and whether or not the shift switches are operating (controls cylinder cutout)

I believe BKR7EKU(dual electrode) are a more reliable spark plug for your engine.

Have you compression tested?
Try putting some ring free in the fuel, helps remove fuel varnish and carbon buildup.

[Cobia270]

Don't forget about the canister filter above the vst tank.

[NAESB811]

thanks, I do have a mechanic coming to test the fuel pressure this week.

The strange part is that the motor cuts out immediately at 1500 where the starboard revs past 1500, even if only on 2 cylinders.

Would the fist check be to verify that 1,4,5,6 are all running in neutral under 1500 rpm (i think 2 and 3 are off in neutral) then check over 1500 to see that 1 and 4 are still running. If 1 and 4 are bad (or plugs are fouled and not lighting) , the motor would rev up to 1500 shut off 5 and 6. the motor would drop below 1500 (because 1 and 4 are not working) and kick 5 and 6 back on.

That would also make sense as to why the motor is topping out at 4200. Could be down a cylinder or 2.

If that is the case, start with swapping a coil to see if that's the issue? If it is sparking just a fouled plug, is there a likely source that would foul 1 or 4 or both more quickly than the rest? Head gasket? Really hope not.

I used the BKR7ES-11 because that is what is on the sticker on the inside of the case. They seam to work fine in the starboard.

thanks

[99yam40]

the starboard motor revs right up in neutral, the port bogs down at 1500 RPMs. why would the engine speed, in neutral with no load, be affected by the # of cylinders?

While i do not know a ton about these motors, I am learning more and more everyday. This forum has been helpful with that.

I have one motor that seams to be running fine right next to the poorly operating one. I try to verify "proper operation" by testing what i do on the port on the starboard.

Rev the starbord in neutral, i can push it as high as i want, I rev the port, bogs at 1500.

I put the port in gear, revs to 4200 (for now until the plugs foul).

Thanks for the input, I appreciate any help.

Have you though about maybe the starboard motor has a problem and is not cutting cylinders as it is designed to do?
I have no idea if it should rev as high as you want in neutral

[NAESB811]

Maybe, but that motor is running fine otherwise. The port is topping out low and fouling plugs. Trying to figure that out first.

I also didn't try to rev it past 3000, just above 1500

[NAESB811]

It appears that my stator has a fried wire on the batter charging side, not sure if that is contributing to the issue but I am going to have it replaced. I just replaced both LP pumps and VST filter as well.

my Yamaha tech to put computer on teh motor. Up to 3275, HP is putting out over 700 psi. At 3650 - 684; 3875 - 657; 3950 - 340psi. On inspecting the cylinders (through the spark plug port), it looks like number 4 is much cleaner than the rest (fuel washed?). He is going to review the info with some guys in the shop. Seeing if anyone here had some thoughts or idea they could share.

could injector #4 cylinder be stuck open or for some reason being triggered open resulting in the loss of pressure? Is it common to have a drastic drop off in fuel pressure rather than a gradual one?

Thanks for any info.


Logging Result
-35 2900 5.03 729.37 1006.9 29.8 BTDC 20 14.06 0.35 1.47 20.4
-31.5 2800 5.03 729.37 1006.9 29.8 BTDC 21 12.16 0.35 1.46 20.2
-28 2700 4.99 718.27 1006.9 29.8 BTDC 24 13.92 0.36 1.6 23.1
-24.5 2925 4.95 718.27 1006.9 29.8 BTDC 22 13.99 0.36 1.58 22.6
-21 3275 4.84 707.17 1006.9 29.8 BTDC 21 13.92 0.36 1.67 24.6
-17.5 3650 4.65 684.97 1006.9 29.8 BTDC 17 13.92 0.37 1.88 29.1
-14 3875 4.57 657.21 1006.9 29.8 BTDC 15 13.92 0.37 1.94 30.2
-10.5 3950 2.39 340.82 1006.9 29.8 BTDC 14 13.7 0.37 2.5 42.1
-7 3950 2.12 313.06 1006.9 29.8 BTDC 14 13.77 0.37 2.52 42.4
-3.5 3925 2.2 318.61 1006.9 29.8 BTDC 14 13.77 0.37 2.46 41.1
0 3925 2.16 313.06 1006.9 29.8 BTDC 14 13.7 0.37 2.42 40.4

[rodbolt17]

nope.
either the VST cannot supply fuel or the filters in the HP pump are clogged.
yes its that simple.

[99yam40]

pressure should not be dropping
Hope for Rodbolt to chime in or someone with plenty of experience with these high pressure units
Pre filter or screens inside pump maybe

Dang I am too slow

[rodbolt17]

did the Yamaha genius actually monitor VST pressure AND HP pressure at the same time?

[NAESB811]

he had a pressure tester hooked up to the schrader valve on the VST tank while monitoring the computer read out but I don't know if he was monitoring it or was fighting with the laptop. I doubt he received his training in the Navy...

from what I have read, mostly from rodbolt17 i believe, The VST pressure need to be at 50 PSI, if it is any less, you will starve the HP pump. If that is the case, check the VST filters, LP pumps and MP pump. I replaced the VST internal filter and both LP pumps. If it's not holding 50 PSI, I should replace the external metal "vst" filter first, try it again, then the electric MP pump?

if that all checks out a need to source some "mystery filters" and replace those?

EDIT: just so I don't have to check it again, does the VST pressure have to stay at 50 psi or does it drop when throttled up? is there a range to check to?

thanks for all the help

[rodbolt17]

50 PSI at ANY RPM.
the HP is the only one with a range.
BOTH must be monitored at the failure RPM and load or the test is worthless.

[NAESB811]

replaced the metal can filter just incase, ran to 3800 RPM, fuel pressure dropped to 260 psi. Removed fuel pump, mailed south for a rebuild. I'll let you know how it turns out.

Thanks for all the info and help.