01 Yamaha 150 hpdi fuel issue

[Cdnpokerface]

I have a 27 foot Sportcraft with twin 01 Yamaha 150 hpdi's. Each engine has 202 hours and I've owned them for half of that. This past weekend while using the boat I was cruising and each engine was running at approx 4500 rpm. Suddenly my poet engine dropped about 1000 rpm and then surged 2-300 rpm before ultimately limiting itself around 1500 I turned engine off restarted and tried again it worked well for approx 3-4 mins and then started the same thing and the engine occasionally bucked. The following day I took the boat out with my fuel pressure gauge attached to the vst and while trying to load up the engine the pressure stayed consistent at 50 psi. After connecting yds up I noticed that there's a code 26 set at the 202 hour mark. I then ran an injector test and all six functioned. After speaking to a fellow member who said he had similar issue I swapped the injector driver assembly with no change. Today I went back to the boat with my laptop to try again this time while trying to load up the engine I noticed the fuel pressure field went red and the value dropped to 500 instead of being in the 725 range, this is when the bucking started and eventually a stall. The engine also is stalling out under idle conditions when driving out of the harbour. Ive read a lot about mystery filters but I'm unsure if the low fuel pressure readings I'm seeing are measured before or after those filters... Any thoughts or suggestions would be greatly appreciated... I'd love the chance to talk one on one with a Yamaha hpdi guru if anyone has a suggestion on that. There are not a lot of hpdi's in my neck of the woods so I'm sorta on my own.

 

[99yam40]

search on the web and Find Rodbolt17 .
he posts on a different forum.

seems to me if the 50 psi stays steady but the HP drops then the screens/ filters on the high pressure pump need servicing. You can send off the HP pump to same places as injectors I think or find someone that will service them.
I am not the person to be giving advice on these HPDI motors though

 

[tommarvin]

Find the closest certified Yamaha outboard mechanic and try to pay for a half hour of diagnosis, then you buy the part and fix it yourself.
Or you could do it online with a certified Yamaha outboard mechanic

 

[naesb81]

in my expirence, if you are not making 725PSI +/- you have a either a fuel delivery issue to the HP pump or an HP pump issue. if you verified that you are making 50 psi under load, i would think it's the HP pump. I had a similar issue, replaced the mystery filters, no joy. I sent the pump to injectorRX for a rebuild, cleared up the issue. I had a bad injector as well, but that's another story.

I would also check to ensure all cylindars are firing when in gear. if not could be a shift poisiton issue.

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

 

[naesb81]

also, did you check your VST filters? if it is clogged it could be starving the HP pump of fuel at higher rpms.