HPDI 150 Help, RPMs Low (Fixed, Maybe!)

[Paul_A]

post # 18, yes I hope you were in neutral as the 2-3 were not firing. I don't believe 875 is too high in neutral in the water because it will drop some in gear. You said you did a sync and link? Is important on that motor as well.

Timing. It doesn't seem like 14 vs 17 btdc would matter until you think about how fast the piston is moving, the air fuel mixture needs to fire at the correct time and those 3 degrees could be part of the problem.

I wouldn't chase anything else until I adjusted the timing to within specs and verified that all 6 have good compression.

Your manual needs to tell you how, I can't remember, been 8 years since I sold mine.

 

[Paul_A]

And I cannot stress it enough. Please verify that every ground on that motor is clean and tight. Saltwater motors are notorious for corrosion and a slightly bad ground on one of the coils will have you chasing your tail.

Also I would carefully pull apart every plug on the motor as well, inspect and then reconnect, click... Just to be sure to check the basics.

 

[seasick]

From my OX66's that fuel pressure regulator becoming clogged I think put too much pressure into the fuel rails. It's the end of the loop that puts fuel back into the VST if I understand it correct, but worth checking if the VST ends up back off.

The OS s and HDPI are different in the fuel area. The HDPI runs about 700 psi after the initial startup. The OX motors have a fuel rail pressure in the 30ish range for the 150. That motor has a mechanical regulator. If there is a screen and it gets clogged, pressure at low speed may be fine but will drop as revs and load is increased. I do not know exactly how the pressure is regulated in the HDPI. To answer a question asked earlier, I believe that the fuel pressure sensor is either in or part of the VST/HSP assembly.

 

[Andrew93]

post # 18, yes I hope you were in neutral as the 2-3 were not firing. I don't believe 875 is too high in neutral in the water because it will drop some in gear. You said you did a sync and link? Is important on that motor as well.

Timing. It doesn't seem like 14 vs 17 btdc would matter until you think about how fast the piston is moving, the air fuel mixture needs to fire at the correct time and those 3 degrees could be part of the problem.

I wouldn't chase anything else until I adjusted the timing to within specs and verified that all 6 have good compression.

Your manual needs to tell you how, I can't remember, been 8 years since I sold mine.

I was trying to tag multiple contributors here but couldn't figure out how, my apologies...

So pulled the boat today and started snooping around. Engine seemed to be a little off in the slow ride to ramp, just a few hundred RPMs off front he other one. Still hoping for the neural safety switch I plugged in the computer and it was acting fine

Also timing was ok according to spec in book. At idle spec is 5 degrees BTDC +/- 3 and it was bouncing between 3 & 4

Pulled plugs as soon as I got home and cylinder #2 was different. Bright white, no evidence of combustion, and an arc mark. All other plugs looked the same. Terrified to run a compression check I did they cylinder first, all 120psi +/- 5 psi, #2 was actually a little above 120.

Attached are pictures of the plugs. Is this as simple as a new plug or more like a coil? I was worried the cylinder wasn't getting fuel where the plug was so clean, but I think I would have no compression if that was the case, thoughts?

I am at the boat until 5ish tonight playing around. I plan on putting in all new plugs but is there a deeper issue

Thanks again for all the help

Andrew

 

[seasick]

just check for spark. there are several ways to do so but a spark checker is the easiest. Other way is to pull boot, insert a screwdriver and hold the shaft of the driver close to metal on the motor. You should see and maybe hear the spark. Try this method on another cylinder to see how a good one looks.
Did you check after running to see if the suspect plug was wet? If not firing due to spark, the plug will get wet with raw gas.
The cylinder is suspicious but it could be a simple as a bad coil.

 

[Paul_A]

That's great news. Something as easy as a coil on an HPDI is a win in my book

 

[DennisG01]

Yup - check spark. You can hold the plug, grounded to the engine block (sometimes hard to see depending on light). But a spark tester tool is a good idea to have on hand.

If no spark, swap with another and check. Is still no good, swap coils and check.

Just out of curiosity, why do you mention the neutral safety switch? I'm not sure I understand how this part is involved with this issue?

 

[Andrew93]

Yup - check spark. You can hold the plug, grounded to the engine block (sometimes hard to see depending on light). But a spark tester tool is a good idea to have on hand.

If no spark, swap with another and check. Is still no good, swap coils and check.

Just out of curiosity, why do you mention the neutral safety switch? I'm not sure I understand how this part is involved with this issue?

The neutral switch on this motor cuts the ignition to cylinder 2 & 3 in neutral and fires all 6 in gear. I guess if there is a fault in the switch it defaults to 4 cylinders all the time, there are a few YouTube videos on it, seems like a common issue. I was curious to if the switch was intermittent.

Waiting to put the toddler down for a nap and I'll get to checking things out.

 

[DennisG01]

OK, maybe there's a disconnect here in terminology. A "neutral safety switch" is what is typically defined as the switch that prevents the engine from starting in gear. I believe/though that the cylinder deactivation is a part of the computer programming? However, it's possible/probable that the computer is looking for input from the NSW to help decide what to do. But then... one would think that the engine wouldn't start at all, if the switch was bad?

 

[Paul_A]

There are two switches iirc.

Neutral safety switch in the control box and a shift position switch by the shift cable in the engine pan.

Again, by memory, definitely check the shop manual

 

[Andrew93]

OK, maybe there's a disconnect here in terminology. A "neutral safety switch" is what is typically defined as the switch that prevents the engine from starting in gear. I believe/though that the cylinder deactivation is a part of the computer programming? However, it's possible/probable that the computer is looking for input from the NSW to help decide what to do. But then... one would think that the engine wouldn't start at all, if the switch was bad?

My terminology is off. Just neutral switch. This video does a good job explaining.

I had spark on all cylinders and plugs. I was again ruling out this switch and my father was in the boat shifting and I had a Ohm meter on the contacts. What I found was that when the shifter was in forward and pulled back into neutral the sliding block did not always slide back enough to contact the switch.

More backstory, some might remember a post I did or contributed to last year about corrosion on F150's. This boat had twin 2007 F150's with the block eaten thorough. Hung these HPDI's a lot cheaper than fixing the F150's. The adjustment ends on the shift linkage looks like it was screwed too far in on the binical side when I looked further into why that neutral switch was not always being engaged.

Still not ruling out a bad plug also, but that coil has spark and tests in rage according to service manual on ohm meter for coil and plug boot.

I am thinking see how the linkage adjustment goes, new plugs, and go out for a test run.

 

[DennisG01]

Ah, OK thanks for the clarification on that switch. Now, looking back at your plugs, though, it appears #3 looks like one would expect in a normally operating system. If that switch was wonky/mal adjusted, wouldn't #3 ALSO be clean, like #2?

When you "got spark", did you verify you're getting spark AT the plug end? Meaning, did you actually see the spark? Did you try swapping plugs around?

I think if you weren't getting fuel, you'd certainly not have good compression by now, given the amount of time it's been run. Peek into the cylinder through the plug hole - how does the cylinder wall and piston top look? Given that is seems logical that you're getting fuel, that brings us back to not having spark...

 

[SoLucky]

I think if you weren't getting fuel, you'd certainly not have good compression by now, given the amount of time it's been run. Peek into the cylinder through the plug hole - how does the cylinder wall and piston top look? Given that is seems logical that you're getting fuel, that brings us back to not having spark...

HPDI's inject oil into the crankcase and it combines with the airflow as part of the intake charge. Lack of fuel would not cause wear to cylinder & rings as y'all are suggesting.

I think the culprit is a bad injector -- one that is stuck shut so you have zero fuel entering the combustion chamber. Or it could be a bad electrical connection to that injector -- check the harness and connectors. By the way, you can buy refurbished (cleaned and tested) HPDI injectors off eBay for around $20/each. Just check feedback and ratings to make sure you are buying from a reputable seller.

Good luck.

 

[seasick]

I thought that the neutral switch on the motor was there to protect the motor when shifting from forward to reverse and the other way around. Yes it does cause cylinders to drop out but the reason is to limit torque during F-R and R-F shifts. I guess it is possible that if that switch is bad, power may be limited all the time as the video implies but that is easy to test by finding the two wire connector and bridging the leads. If the motor makes good top end revs and power, the switch needs replacing. I don't know how often that switch fails but misadjusting the neutral position is a more common cause especially after new control cables are installed

 

[DennisG01]

If that's true, Lucky, that solves the mystery right there - thank you. For some reason, I though the oil/gas was mixed before the injectors in the HPDI.

A different way to go about fixing a bad injector is to have them professionally cleaned/rebuilt, as well. It's about the same cost ($20) but at least you know you have good quality injectors. Most decent sized cities will have injection shops that can do this - and they do this day in and day out. There's online places, too.

 

[SoLucky]

For some reason, I though the oil/gas was mixed before the injectors in the HPDI.

If it worked that way in a DFI 2-stroke, the bottom end (crank, connecting rods, cylinder, rings, etc.) wouldn't get oiled...

 

[DennisG01]

If it worked that way in a DFI 2-stroke, the bottom end (crank, connecting rods, cylinder, rings, etc.) wouldn't get oiled...

(I shouldn't have said "if" that's true - that's just the way I worded it).

I know, that's what's kind of funny here. HP "DI" - right there in the name and I wasn't even thinking of that!

 

[Andrew93]

HPDI's inject oil into the crankcase and it combines with the airflow as part of the intake charge. Lack of fuel would not cause wear to cylinder & rings as y'all are suggesting.

I think the culprit is a bad injector -- one that is stuck shut so you have zero fuel entering the combustion chamber. Or it could be a bad electrical connection to that injector -- check the harness and connectors. By the way, you can buy refurbished (cleaned and tested) HPDI injectors off eBay for around $20/each. Just check feedback and ratings to make sure you are buying from a reputable seller.

Good luck.

I was thinking a stuck injector too when I saw the plug but when compression was good I wasn't sure, but oil injected on its own makes sense. All injectors were all tested and cleaned beginning of this season by FuleInjectorMan.com. I will look into this more before boat goes back into the water, but when running in a bucket in the yard for 10-15min plug did appear wet when taken back out. The injector did trigger when activated on the computrer but I guess that would not say if it was operating correctly. I was trying to hold a paper towel to the spark plug holes to see if it was wet after cranking but I could not determine one way or another on any cylinder. I did see those cheap ebay injectors but they made me a little nervous also where OEM is 10x that.

I did check spark against block. Spark at plug and in a spark tester, and coil and boot in spec on Ohm meter. If there was no spark but it was getting fuel would the injector look that clean? When it came out the plug almost look like it had gap bridging, maybe it got loaded up quick and ceased to fire right? When I tested spark against the block the little piece of carbon seen was removed, should have left it to see what it did, oops. The photo below is zoomed in right after it was removed.

 

[SoLucky]

You can always put fresh plugs in and take it for a spin... see if that makes a difference before going down the path of checking the injector.

If your injectors were cleaned and flow & spray pattern tested recently, then I would start on the electrical side of things and make sure all connections are clean and solid and that the harness appears undamaged. If that all checks out, then swap in a different injector (maybe one from the "good" engine) and see what happens.

I have had very good experience buying refurbed injectors off EBay for prior Yamahas (4 strokes) as well is my current HPDI. I hear your hesitancy given the cost difference vs a brand new Yamaha-brand injector... but as I said I've had good experiences.

 

[DennisG01]

Since you physically saw spark at the plug, it's a safe bet that that side of things is good. There's obviously no combustion process happening inside that cylinder, based on the spark plug. The dark part is probably just burning oil and the dark spot was probably the "bottom" of the plug inside the cylinder (gravity). So... you have spark and I'm sure you have air... the other variable needed to make fire is fuel. That has to be the missing piece, right?

I like the idea of swapping an injector - whether it's on land and then try the paper towel trick (does that work for the known-good cylinders) - or go and run the boat.