2006 Yamaha 250 HPDI mystery filters

[richierich1]

​Hello,

looking for a little help on my 2006 250 HPDI, Lost power at 4500 RPM coming back home idled back to launch ramp. Had Motor looked at and had three fouled plugs. Had plugs replaced as well as impeller etc 120 compression on all cylinders, motor has about 350 Hours on it. The plugs were replaced prior on 2/18 as well as the VST filter and the other filter. I run 89 octane good quality fuel as well as ring free. Boat has ben run 8 times a month since 2/18.The motor has all updates and the oil injector pump was replaced as an update in 2009.

I have never had the injector mystery filters changed out, my question is do you change out your mystery filters and have you ever found a clogged filter?


My mechanic has said he never had a injector filter clogged. He stated the other two filters normally catch any fuel problems. So I was wondering my options are to run a separate fuel tank and see if that makes any difference as I was told that was one way to diagnose the problem by separating my fuel system (tanks).

I have read faulty or intermittent sensors do not show up as troubleshooting codes at times. I am not sure if I am looking at a new high pressure fuel pump or what? I feel like I am getting into a "repair loop"

Any insight would be appreciated!
Respectfully, Rich

[Rickp]

If wa mine I'd send them in to get cleaned and calibrated. 35.00 to 45.00 each and you
will notice a difference.

[Ranger519VS]

Good idea to get the injectors serviced. They usually fail toward the rich side and that could explain the fouled plugs.

[FishWhisperer.]

Agree with the two previous answer. Get your injectors serviced. You wont regret it. Have you checked the mechanical lift pumps. You replaced the filter in the VST, the high pressure filter on top of VST and the element filter before fuel pumps? There is also a basket style filter on the pressure regulator. Have you ever had the high pressure pump oil changed. What's your fuel pressure? When was the last time you serviced O2 sensor?

[CJ1]

No o2 on a hpdi. Cj

[mikeky]

No o2 on a hpdi. Cj

Can't say that all HP's do but my 175 HPDI has one.

[Rickp]

250 and 300 don't, 225 and smaller do.

[FishWhisperer.]

I will admit I wasn't sure if his model would have one, my 175 does. It funny how in less than 12 hours I get as many replies to correct me as the OP to assist in his issue.

[richierich1]

Thanks for the responses. I currently am having the injectors cleaned and serviced.

I replaced two filters, the VST and the primary, on 2/18 I will ask mechanic to replace other filters that have been mentioned. Through my research I thought there was only two filters and then the injector mystery filters. I am going to research the filters today as well.

We did talk about sensors and them possibly being bad I will ask him if this 2006 HPDI does have an 02 sensor.

The technician at Injector RX stated that their is a fuel pressure sensor, a VST relay as well as a low pressure sensor. He stated the fuel pressure coming from the low pressure to the high pressure should be 48-52 PSI.

I will ask the mechanic as well what fuel pressure PSI is coming out of the pump. I spoke with the technician at injectorRX and we had the same discussion.

The oil injector pump was replaced in 2009 as a factory update.

For people wondering this motor has run beautifully never had fouled plugs and only once while running WOT did I feel the throttle bogging down at top speed which is when I had my two filters replaced in 2/18.

Hopefully this thread will help others, I am trying to stay out of the replace parts loop and hopefully get back on the water ASAP.

Respectfully, Rich

[yam911]

No o2 on certain hpdis. Cj

There. Fixed it for you.

[yam911]

Some 225's, 250 and 300 don't, some 225's and smaller do.

There. Fixed it for you.

[yam911]

Why are filters in the HPDI mechanical fuel pumps called "mystery" filters while filters in the fuel injectors are not called "mystery" filters?

[richierich1]

The filters in the injectors are called the "mystery filters" small filters that you have to insert a screw or bolt into and then pull them out and replace them. They are located behind the fuel rail. According to the youtube video there is a mystery filter in the fuel pump and one on the right side of the pump as well.

[FishWhisperer.]

Personally I wouldnt refer to the filters in the injectors as mystery filters. They all have them. If anything maybe the 2 filters in the high pressure pump. Or perhaps it's because they're not available from Yamaha thus not on a parts diagram on google. There are no filters in the mechanical lift pumps.

[yam911]

My point is, those that know Yamaha motors have always known about the mechanical HP pump filters. Just like the injector filters are known about. But why and when did they start being called "mystery" filters?

[CJ1]

There. Fixed it for you.

Thanks! Didn't know that on the smaller ones! Sorry for the bad info, hate that. I should have said on the 300's and 250's I have had my hands on. Cj

[CJ1]

I will admit I wasn't sure if his model would have one, my 175 does. It funny how in less than 12 hours I get as many replies to correct me as the OP to assist in his issue.

Sorry, I just didn't want the o/p looking for something he doesn't have. As I was 99.9pecent sure a 250 hpdi does not have one. I'll go away now��.cj

[Rickp]

Thank you Boscoe

[richierich1]

Update

Had six mystery filters changed out today and ran the lake,same problem hit the wall @4200 RPM. Next chore, hook the system up to the YDS (computer) and check the high pressure pump. Found out there is two low pressure pumps, a medium pressure pump and a high pressure pump.

Man those mystery filters are tiny! You have to love getting out on the water to put yourself through this :)

[richierich1]

UPDATE

Had mechanic use YDS computer system and check out the High pressure pump, high pressure pump working perfectly as well as the two low pressure pumps and the mid range pump. Next we are going to change out the cranking battery which showed defective via battery tester 48 months into a 36 month warranty. The boat will be run on the water with a separate fuel tank tomorrow.