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Another....HPDI Loss of Power

Old 08-03-2016, 07:12 PM
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Default Another....HPDI Loss of Power

I know there has been numerous threads on this subject but I just wanted to get different opinions on my particular situation. I have a pair of twin 2004 Yamaha HPDI 200s. Roughly 1000 orginal hours on each with roughly 700 hours on the starboard head. (Replaced under warranty). My port motor which is orginal power head, is only getting around 4600RPM where as the starboard motor will get up to around 5000 WOT. (Still not where I would like to be) Motors run great at cruise speed with some throttle adjustment. Also starting from an idle with only one motor, the starboard motor will get the boat up on plane alone, where as the port motor will only get up to roughly 2700 and not plane the boat by itself.

I have gone through different things on the motor to try and resolve the issue, such as cleaning o2 sensor, had injectors cleaned, high pressure pump cleaned, new fuel water seperators, and replaced all spark plugs. This week I will be cleaning VST and replacing low pressure fuel pump but unsure this will resolve the issue because of normal fuel pressure. Yamaha diagnostics have been hooked up and read good fuel pressure, with everything looking normal. Only hiccup I have noticed is coming in the other day at idle before doing any of the above, the port motor started to have erratic idle and would shut off a couple times but fire Right back up. Ran rough for a few minutes and then right back to normal idle almost like it had bad fuel.

Props are 19P Yamaha SWS. If anyone has any thoughts, it would be appreciated.
Old 08-03-2016, 07:28 PM
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Lp pumps and VST are a good place to start but you are fortunate to have twins so you can move things back and forth one at a time to see if the problem follows. I would start with the TPS if the filters and pumps don't fix it.
Old 08-03-2016, 07:37 PM
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Link and sync. The screw you undo on the butterfly to set it is LEFT HAND THREAD. Screw it "in" to loosen. Don't even ask how I know.
Old 08-03-2016, 08:22 PM
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I would check the spark plug power pack. There is one for each plug and they are known to fail. They sit on the back of the engine behind the center panel.
Old 08-04-2016, 05:01 AM
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Originally Posted by Knot on Call View Post
Lp pumps and VST are a good place to start but you are fortunate to have twins so you can move things back and forth one at a time to see if the problem follows. I would start with the TPS if the filters and pumps don't fix it.
I will check the TPS after the VST and pumps if it does not resolve. I have also read up on the shift position swtich going bad but not sure if I would still reach 4600 RPM if that was the issue.
Old 08-04-2016, 05:03 AM
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Originally Posted by StPeteRebel View Post
I would check the spark plug power pack. There is one for each plug and they are known to fail. They sit on the back of the engine behind the center panel.
Easy way to check them? You talking about the ignition coils?
Old 08-05-2016, 05:35 AM
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A compression check would be easy to do and might identify a problem cyl. Should have 110-125 PSI.

When you changed spark plugs did you notice any difference in their appearance? Any of them have more black carbon deposits than others?

Get a spark tester to verify there is spark, do this running the engine on muffs. Remember, the HPDIs idle on 4 cyl, 2 & 3 will have no spark idling in neutral. Engage forward (I remove the prop during this test), make sure 2 &3 now have spark. This test also verifies the shift position switch is working or not. Shift pos sensor tells the ECU to enable spark to cyl 2 & 3 when in gear. It is common to have the shift cable out of adjustment thereby causing a shift position sensor issue.
Old 08-05-2016, 06:46 AM
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Originally Posted by keywest49 View Post
A compression check would be easy to do and might identify a problem cyl. Should have 110-125 PSI.

When you changed spark plugs did you notice any difference in their appearance? Any of them have more black carbon deposits than others?

Get a spark tester to verify there is spark, do this running the engine on muffs. Remember, the HPDIs idle on 4 cyl, 2 & 3 will have no spark idling in neutral. Engage forward (I remove the prop during this test), make sure 2 &3 now have spark. This test also verifies the shift position switch is working or not. Shift pos sensor tells the ECU to enable spark to cyl 2 & 3 when in gear. It is common to have the shift cable out of adjustment thereby causing a shift position sensor issue.
Most of them had a little bit of black carbon build up on them, there was one that was clean and wet though that would mean either that cylinders not firing or running lean, correct?

I did compression check a couple months ago and all cylinders were within 5-10% of each other. I will check again.

So if I check for spark on each cylinder, and there is no spark on 2&3 when in forward, then I have a shift position switch issue? This will be the next thing that I check.
Old 08-05-2016, 06:57 AM
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I have an hpdi as well, and when I had 1 clean spark plug like you mentioned, I had a problem with the head gasket leaking water into that cylinder and not allowing to it spark. Was noticable at the upper rpms. Had the head gaskets changed and has been running great since.

Originally Posted by ReelAddiction28 View Post
Most of them had a little bit of black carbon build up on them, there was one that was clean and wet though that would mean either that cylinders not firing or running lean, correct?

I did compression check a couple months ago and all cylinders were within 5-10% of each other. I will check again.

So if I check for spark on each cylinder, and there is no spark on 2&3 when in forward, then I have a shift position switch issue? This will be the next thing that I check.
Old 08-05-2016, 07:01 AM
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The only way to diagnose a HPDI is with the software and a fuel pressure gauge.

Its pretty easy once you have those two items total cost less then $ 200.00

The process goes like this:

At the problem rpm do you have 50psi on the VST and more than 625 psi on the high pressure pump, if yes then its electrical ( plugs grounds drivers etc.)

If you have 50 psi at the vst and less than 625 psi on the high pressure side then it is either the medium pressure filter or the mystery filters in the high pressure pump or maybe the pump itself.

if you have less than 50psi at the vst then it is either:

The vst electric pump (can you hear it click on and give 50psi with the key on)

vst filter the yellow screen (can of carb cleaner with the last 1/4 bent at 90% spray like crazy while moving the straw around through the vst drain hole) the yellow filter sits above the drain hole

Low pressure pumps: does the primer ball get hard if not the pump most likely are toast , you can remove the pumps and look at the back sides while pumping the primer ball , if you see fuel drip out its bad

The low pressure filter and filter housing are you sucking air ? , make sure you can see no threads on the filter housing. You freeze the cup before you try to re-assemble, fuel swells it and it is a pain to get together and air tight unless frozen

Racor filters sucking air, fuel tank vents clogged or the anti syphon valve in the fuel tank is stuck are some other possible problem spots.

Most of this info is from Rodbolt a master yamaha tech who posts on some other boards.
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Old 08-05-2016, 12:28 PM
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Originally Posted by ReelAddiction28 View Post
Most of them had a little bit of black carbon build up on them, there was one that was clean and wet though that would mean either that cylinders not firing or running lean, correct?

I did compression check a couple months ago and all cylinders were within 5-10% of each other. I will check again.

So if I check for spark on each cylinder, and there is no spark on 2&3 when in forward, then I have a shift position switch issue? This will be the next thing that I check.
RE clean and wet plug.

I would certainly make a note of which cyl had this plug. They should all look about the same.

RE shift position switch

Yes, if you have no spark on 2 & 3 when in gear then this switch may be the reason. However, an out of adjusted cable can cause this too. The service manual has a section dealing with adjustment.
Old 08-06-2016, 08:27 AM
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Well thank you all for the input, ended up cleaning the VST and replacing lp pumps. Then at the same time went on to test all cylinders were firing (which I thought I had done at the start of these issues) and found out that #2 was not firing. Switched the ignition coil from a cylinder that was firing and found out that was the problem. Had an extra coil sitting around so I threw the new one on there and all was good! Took her out and got 5600 RPM on the port motor that was only getting 4700, and 5400 on the starboard motor. Now looks like VST, injectors, hp pump, lp pumps, don't sound like a terrible idea for the starboard motor.
Old 08-06-2016, 08:48 AM
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Thanks for posting the solution, now go fish!

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