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

[Andrew93]

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.

I am going to do some more experimenting with the paper towel trick when I am back at the boat this weekend. New plugs also in that cylinder. Being frugal swapping the injectors requires $30 in non-reusable gaskets. Grand scheme of things thats nothing but still, haha. Seems to be screaming injector otherwise, and if thats the case I won't have one for this weekend unless I go get a new one at the dealer $$$.

I am eager to get this right for the end of the season too, we are in the market for a Marlin or maybe a 282 Sailfish and want this boat 100% to list if its replacement comes along. We are hoping to buy the replacement then sell this after.

 

[seasick]

That plug looks like crap. Do all of the plugs have the same erosion of the electrodes?

 

[Andrew93]

No, that one plug was beat up, the others were discolored from combustion but not eaten away like this one.

Here is my current theory but it's just that, a theory. Shift linkage was was off causing cylinder 2 & 3 not always to fire. Cylinder 2 plug was fouled and possibly gap bridged causing no spark, cylinder 3's plug never fouled and worked when the intermittent switch/linkage issue wasn't a problem. Cylinder 2 with the "bad" looking plug was just getting sprayed with fuel and plug was never igniting and sort of welded itself together.

I wanted to test that plug with that slag on it but my father knocked it off with his pocket knife before I could say stop. If that plug had no spark with that chunk on it it would make sense and it welded to itself.

Linkage readjusted, new plugs, and I think give it a go. If still an issue a new injector is next. If that doesn't fix it then damn I don't know!

 

[seasick]

I hope the issue clears up. I am not sure what would beat up that plug so much more than the others with the exception perhaps of detonation. If the compression in that cylinder is still good that is a good thing. Let's see how the test run goes. Fingers crossed.

 

[DogBone]

Fire93Medic, did you finally resolve the problem? Was it a bad injector?

 

[Andrew93]

Fire93Medic, did you finally resolve the problem? Was it a bad injector?

I know I haven't updated my issue but I am still trying to figure it out. Boat being an hour away and a toddler doesn't help being prompt, but I worked on it this weekend.

From my most recent post I replaced plugs, adjusted the neutral switch, and confirmed spark in that cylinder. Back in the water with same results. I swore I hooked the motor to YDS and confirmed I heard all injectors firing in the stationary test...

I figured that one injector must be bad so I ordered one from Injector Rehab all serviced and ready to go. Put it in with new gaskets, the new plug looked like the old one I took out, a lot of arching and white. I took the boat out and now its worse! Started hard and won't go above 2000rpms. Friend took the helm while I hunted around for a loose connection, seemed cylinders 2, 4, and 6 all dead. I know I had spark where I got nailed by a coil once or twice haha.

Pulled the boat back home, hooked to YDS and cannot get injectors on cylinder 2, 4, 6 (all port side) to fire at all on stationary test. Confirmed all plugs in place, no loose or chaffed wires, and even pinned them out with ohm meter from injector driver plug to injector plug, all good.

I ended up taking the injector driver out of other motor and swapping, problem went with the driver. Ordered a used driver off eBay today with returns accepted if defective ($1500 new, $175 used, worth the risk). Maybe the driver was on its way out and not firing cylinder 2 at all and me moving it around some did it in? I opened the "bad" one up and thought I smelled burnt electronics but that could be my imagination.

Frustrates me that I made it worse this weekend by simply replacing 1 injector. I hate just throwing parts at it like this too, but I feel I might be onto something maybe...

The injector driver should be here by the beginning of next week. I plan on putting it in, hoping for the best and going for a ride. If all is good away she goes for the winter.

 

[seasick]

This new symptom is odd and has to be related to something you recently did. In any case, the first step would be to verify that the coils are good. You can swap one from the other bank but I advise against pulling off the plug wires and leaving them hang loose. Get a cheap spark tester.
Check the harness and connectors that feed the coils also and while checking verify that the grounds have all been connected to the head.
Next step would be to check the pulser output. You need a service manual to understand what to test and what measurements to look for.

 

[Andrew93]

This new symptom is odd and has to be related to something you recently did. In any case, the first step would be to verify that the coils are good. You can swap one from the other bank but I advise against pulling off the plug wires and leaving them hang loose. Get a cheap spark tester.
Check the harness and connectors that feed the coils also and while checking verify that the grounds have all been connected to the head.
Next step would be to check the pulser output. You need a service manual to understand what to test and what measurements to look for.

I agree it seems like something I did but for the life of me can’t figure it out. I have spark on all cylinders but no fuel injector activation on 3. The pulse coil fires 2 cylinders at a time it seems so if that was bad I do not think I would see problems isolated to to one whole side, but in pairs on opposite side, if I remember correctly from the service manual. I was not able to get injectors to fire with YDS but when injector driver was moved to other motor the problem went with it in static testing in the yard

I did have to move the driver to the side to gain access to injector and I checked all connections if something was loose but everything looked ok. At this point I ordered the used driver and will wait and see what happens there before I go anywhere else. I will check spark again but it was good initially after the new injector and with this issue.

 

[Andrew93]

Today I replaced the injector driver for the engine. Attached are before and after photos of the same plug. The before photo is of the plug after running the boat 10 or so hours variety of conditions. The after it was run for 30min, maybe 10 of that on plane.
I agree the injector driver failing seems unlikely but I feel good that it’s fixed. With these motors new to me this season I think the previous owner was having symptoms and didn’t tell me, and I went off a compression check and not a sea trial so I could pick them up easier 6.5hrs away.

Both motors are about equal in throttle position and 5000 rpm’s. My RPM issue now I think are props, it has 19p and I think I need 17’s

Thanks for all the help here. Boats going away for the winter and we will see what the spring brings with it unless I find my future Marlin!