8.1 GXI-J Cranks but No Start w/ Diacom Logs

[tpenfield]

I took a look at the 2 Diacom recordings . . .

First there is not any info on the Crank & cam sensors other than the fault codes.

What I did notice is that the ECT readings do not go up until the engine has been running for about 8 minutes. This seems like a long time for the cooling water not to show any temperature rise. As it was, the temperature rose to only 126˚F and then started to come down. Maybe t-stat is stuck open?

So, I am not sure if the ECT is a symptom of a problem, or part of the problem.

The second recording showed engine cranking. The RPM reached 162, which should allow it to start, and the injector pulse width was 30+ ms.

Has there been anything done to the cooling system recently? It would also be good to use an IR temperature 'gun' and get some temperatures with the engine running and warmed up. Also, verify the helm gauge vs. the ECT values. I believe the temp gauge would have its own sender, not part of the engine control sender.

Basically, the ECU 'thinks' the engine is cold and is setting the injector pulse and RPM accordingly . . . both a bit higher than 'normal'.

Hopefully, the 2 new sensors will show improvement, and maybe the ECT readings will clear up as well.

The two sensor voltages (5.01 and 4.10) look fine, or at least consistent with the last issue (knock sensor).

 

[apisk]

Okay well I changed the sensors and pretty much have a whole lot of bad news

Attached pics show both sensors and how gunked up they were

After changing the sensors, the engine started up the first time as usual, continued to run rough, and once I turned it off and attempted to re-start, it never did (exact same behavior as before I changed the sensors) Additional Diacom log of trying to start below as well

Volvo EGC CAN ETC 08 31 2023 10 07 55.rec

drive.google.com

After the non successful starts, I began to just look around and I found some water leaking from what appears to be a head bolt. I went to tighten it, and it just kept spinning. Upon pulling it out, the bolt was already snapped off broken (attached pic). Also attaching where the bolt came from if someone can confirm it was a head bolt

Based on the suspicious gunk on the sensors, I checked the engine oil dipstick and it was covered in the same white milky gunk

TLDR, I think my engine is done for

 

[apisk]

I had the engine oil changed at the start of the season, and the entire manifolds, risers/exhaust setup changed in May where no issues were found. I don't know if the head bolt issue led to leakage since then and the engine was just a ticking time bomb, but it really appears the engine is done for - am I unfortunately accurate in that assessment?

 

[tpenfield]

Oopps . . .

Yes, go ahead and run a compression test if you want, but it sounds like the headbolt snapped . . . Maybe from a hydro-lock?

Looks like you will be having some re-build or perhaps a new engine. This discovery may explain the ECT gauge funkiness.

 

[apisk]

As you see in the pics, both sensors were caked with the same milky substance, so does that mean (I think I know the answer) that water got into the crank as well as the cam? Where are the leak points for water to get into these areas? I am trying to understand what "broke" that led to this. You are right, the ECT behavior makes sense, and the sensors being flagged makes sense because they were completely covered that they couldn't get a reading

 

[alldodge]

That's a bummer
Head bolts usually only break if it was over torqued during assembly, in this case from the factory. Guess there is also manufactures defect with the bolt

 

[apisk]

That's a bummer
Head bolts usually only break if it was over torqued during assembly, in this case from the factory. Guess there is also manufactures defect with the bolt

I have only owned the boat for 4 years so I am not sure if any work was done by the previous owner, but I would doubt it with the low hours. It is so odd that the engine still starts the first time, but after it won't - Does it get filled with water from running then causing it to not start the subsequent times? (not usually, but in my situation at least)

 

[ESGWheel]

... so does that mean (I think I know the answer) that water got into the crank as well as the cam? Where are the leak points for water to get into these areas?

While unsure what the initial cause to break that bolt, it resulted in a lack of proper clamping between the cylinder head the block. This clamping force does several things including compressing the head gasket that keeps the combustion pressures in the cylinder and keeps separate the oil and water passages that flow in the block & head > i.e. keeps the oil and water from mixing. When coolant (water) is allowed to mix with the oil, that contaminated oil will get into the camshaft and crankshaft and everywhere else oil is used in the engine. Here is a link for lube system flows. You can find similar sites taking about coolant flows.

 

[tpenfield]

Just thinking about the head bolt . . . You've had this boat/engine for 4 years, so it must be something that happened recently. Otherwise, it probably would have manifested itself long ago.

So, what are your next steps?

 

[apisk]

Just thinking about the head bolt . . . You've had this boat/engine for 4 years, so it must be something that happened recently. Otherwise, it probably would have manifested itself long ago.

So, what are your next steps?

That's what is confusing to me, the boat has been running amazing up until the recent string of events. Is it possible that the heavy shaking/vibration getting off the sandbar was enough to break the headbolt (which may have already been vulnerable?) - or would something else have caused the bolt to be worn down to begin with?

The local marina that does all my work is going to let me know this weeks a few options around re-powering, re-building, diagnosis etc but I think that since the crank and cam sensors were so caked, those internals are going to be rusting out so the entire bottom end may be shot

 

[alldodge]

I think that since the crank and cam sensors were so caked, those internals are going to be rusting out so the entire bottom end may be shot

Not necessarily

 

[apisk]

Not necessarily

That would be great news, but if those sensors are caked, wouldn't that mean water is in those areas?

 

[alldodge]

Yes, but it's water but mostly oil. Even if there is a slight bit of rust that would be removed during machining process.

If it is a rod knock then the ones with spun bearings need reconditioned or replaced.

As Bondo mentioned, remove the drive and run motor to make sure its the motor

 

[tpenfield]

The engine can probably be rebuilt. No need to make predictions at this point

 

[apisk]

Yes, but it's water but mostly oil. Even if there is a slight bit of rust that would be removed during machining process.

If it is a rod knock then the ones with spun bearings need reconditioned or replaced.

As Bondo mentioned, remove the drive and run motor to make sure its the motor

I don't have a trailer or access to do that unfortunately, so I will be relying on a local marina hopefully this week - are there any specific things or tests I should ask them to focus on? At this point with these kind of issues I am a bit over my head.

Are there other areas of the engine or parts that can be checked that would show the severity, or that can only be done once someone starts to take things apart?

 

[alldodge]

If it's going to take a bit of time before motor is getting work, I would have the oil changed with some cheap oil. This is just to get some more of the water out. Change and start for a minute then shut down

With water in the oil the motor will need to be taken a part until the area is found.

Normally start with the heads and hope its just a blown head gasket. If it is then head work, gaskets and it goes back together

 

[apisk]

If it's going to take a bit of time before motor is getting work, I would have the oil changed with some cheap oil. This is just to get some more of the water out. Change and start for a minute then shut down

With water in the oil the motor will need to be taken a part until the area is found.

Normally start with the heads and hope its just a blown head gasket. If it is then head work, gaskets and it goes back together

I keep getting push backs from the marina so I may need to find someone to come do an oil change in the meantime

Outside of the blown head gasket, are there other common areas of failure I should look into?

 

[alldodge]

Sure the head or block could crack but would not be expected from what has been listed. A oil change pump is cheap enough, could do your self

 

[tpenfield]

What sort of push-back are you getting from the marina?

 

[apisk]

What sort of push-back are you getting from the marina?

Just scheduling, I am in NJ and the Atlantic City in water boat show is this weekend, so they are mostly getting ready for that personnel wise. I didn't think their mechanics had anything to do with that show (just an excuse they're giving it seems), which is part of the push back I am giving them, so hoping worst case to have it over there next week