HPDI Missing

[bls-fla]

One of my 2000 150HP HPDIs is missing above 2100 rpm. The other motor is fine so I've discounted common fuel supply. I've changed plugs and changed fuel filter. Idles fine and runs all day around 2000 rpm. Soon as I go over 2100 rpm it really breaks down. Any help appreciated.

[boats.net]

If you Yamaha gauges with warning indicators then make sure the overheat or low oil warning is not activated. Have fuel pressure checked and computer diagnostic run on it to see have fuel pressure problem.

[bls-fla]

HPDI Missing follow-up

Thanks. One thing I'm considering is that one of the two oil pumps that feed the VSP is bad. Someone suggested that this could cause it to run OK at slow speed but not supply sufficient fuel at higher speed. As far as I know the pumps are 10 years old so a possibility maybe. Sound reasonable? No alarm indications.

[Hollywoodfish]

When you say missing, do you mean surging? Does the motor load up and then drop a few 1000 RPM's then load up again?
If that is the case, then you should look into changing the VST filter (and O-Ring). From experience ive done this about 5 times on my twin 2001 150 HPDI's. Do it yourself, not that hard of a job.

[bls-fla]

I relate it to my many years with auto engines. It feels like a misfire but you could be spot on, it may be surging. Surging in my mind means it tries to speed up then bogs down, does that sound right? Would it be surging on acceleration but OK idling? In fact I was out for 2 hours cruising the ICW and it was fine under 2100rpm. I suppose it could be doing either or both. I have little fear of going at the VST; however, I've gotten new mechanical fuel pumps and will try those. If you've changed the VST filter on your 2001 5 times that says a lot. I've only had these motors 6 months and don't know if the filters have ever been changed. How about the external filter or strainer? Thanks for your input, your suggestion will be my next effort.

[Hollywoodfish]

When "we" were going through the change over to E fuel I had a lot of issues. Over the course of about 6 years I went through 5 VST filters and even a set of fuel pumps. I attribute the burning out of fuel pumps to the clogged VST's. I got the tank flushed and cleaned and replace my Racor filters every 50 hours. So far, Ive gone over a year with (knock on wood) no fuel issues.
My engines would be fine (at *****ing speed) but when it was time to pick up and run, the surging would start and my blood pressure would spike. Sounds like you have the same issues as I did many times over. Good Luck an let us know.

[bls-fla]

More I read the less I know. I've ordered a new strainer, VST o-ring, and the new low pressure mechanical pumps. I will attempt to clean the filter in the VST. While waiting for the parts I began to wonder if it is possible or maybe even advisable to open up the VST without removing it? If I don't remove the VST can I get to both of the mounting bolts for the upper low pressure mechanical filter and will I be able to put on the new gasket? Anything else I need to consider? This board has been very helpful to me and I do appreciate the experienced input.

[NATES]

When I service my VST, I leave the top in place & remove the bottom tank. The whole job takes 40 min. Send me a e-mail address & I'll send pictures.

[bls-fla]

HPDI follow up

Nates, thanks for the photos. They helped and the job was easy. Had to leave town and got involved in other junk so I'm just getting back to my problem. I've replaced both mechanical pumps, serviced the VST, replaced the strainer, and of course the filter. Nothing jumped out at me but hopefully I fixed the problem. However, after getting everything reassembled and before starting I pumped up the bulb to look for low presure leaks. Immediately I saw fuel leaking from the thing called a fuel feed assy., it's between the filter bowl and the two mechanical filters. The leak is coming from a seam on the fuel feed assy. body where 2 different colors of plastic are joined, it's not coming from the fittings. Anyone know what this thing does? Since the fuel can't pass through the mechanical pumps without starting the motor am I just getting back pressure and will it stop leaking? Thanks all for previous help.

[mitch]

if its leaking fuel out it will also suck air in should not be leaking

[Hollywoodfish]

BLS -FLA What is the end result? Did you get your issue resolved? let us know.

[bls-fla]

HPDI Missing follow-up

I did get the issue resolved, in the process I replaced pretty much everything up to the strainer after the VST. The VST I serviced and it looked OK, the components I replaced seemed OK but can't be sure about all of them. I did find a plastic fitting called a"fuel feed assy." had a hairline crack(leak) in a seam but I may have done that myself, I didn't see the leak earlier. I don't like not knowing for sure what the problem was but I'm back on the water. Servicing the VST turned out to be a piece of cake, thanks to all for the advice.