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

[apisk]

I have a 8.1 GXI-J Volvo Penta and took the boat out on Saturday for a ride where after about a minute on plane the boat died on me, alarms went off, and would not turn back on. After waiting a few minutes, the boat did start back up and I was able to get it back home to my dock. The boat starts once each morning (Sunday and today) but after that, it will not start again. A few things I observed below:

- after the boat died, I came back at the lowest speed possible, but as I attempted to accelerate to see what would happen, the ECT/coolant temps would drop from the 150/160 range down to 100, as soon as I let off the throttle back to the lowest speed, the temps crept back up (I tried this a few times, consistent each time)
- when the boat died, 2 alarms went off - when I plugged in my Diacom once I got home, there was a "Crank Sensor Fault" code and "Cam Sensor Fault" code
- when trying to start the boat after the first time, the "engine speed RPMs" within DIACOM never go above 200 rpm - I read somewhere that it needs to be in the 200-300 range for the engine to know to start - is this true? Would that be a bad crank sensor signal?
- the batteries are fully charged, 3/4 tank of gas, starter is actively cranking, fuel pump is priming, it just won't turn over

I have 2 Diacom logs below. The first one, is after the boat ran for 10 minutes, then I turned it off and immediately tried to re-start and it wouldn't. Towards the end of the 10 minutes you will see the ECT/coolant temp fluctuations I mentioned above where they would drop and rise a few times (the boat sat in idle the entire time). You will also see the 2 Codes that were flagged. The second log below is just me attempting to start the boat a few times. Video also attached of attempting to start

Volvo EGC CAN ETC 08 28 2023 09 01 33.rec

drive.google.com

Volvo EGC CAN ETC 08 28 2023 09 14 40.rec

drive.google.com

Doing some digging on this forum and online, I saw some tips that if the Crankshaft position sensor is bad/off then it won't allow the engine to start. Does anyone have insights into this? If anything else stands out from the logs please let me know

@muc @alldodge @tpenfield as you were all extremely helpful with my last issue

 

[tpenfield]

I have my Diacom computer on my boat and will be there in the next few days, so will look at the recordings then.

Some initial thoughts . . .

Probably not going to worry about the ECT at this point, because you have some hard faults for the Crank and Cam sensors. If you clear those faults, do they come right back?

As for the starting RPM needing to be 300+ RPM . . . no, not in my experience, as the starters usually crank the engine at about 200 RPM. On many engines, the engine control systems 'take over' once the engine gets to 300 RPM, so that is when the first few cylinders are firing. Before then the timing is in a 'starting mode' (I forget what it is called), which I believe is analogous to 'base timing', and the injector pulse is set at a fairly high level. So, if all else is good, the engine should be able to start even if it is below the 300 RPM cut-over.

Maybe post what fault codes you got, and hopefully the other guys will have some comment and next steps.

Aren't these hi-tech engines fun?

 

[apisk]

Attached are the 2 codes that were flagged. I have not tried clearing them yet since I can't get the engine to start a second time I didn't want to take a chance of taking it out for a trial until I can get clean consistent starts. I wasn't sure these were preventing the engine from starting because it does start once, but then each subsequent time after that it won't (until I check again the next day)

 

[apisk]

I also read that the CKP will prevent the engine from starting, is it possible the sensor is having issues causing the inconsistent starts? Is this sensor right above the raw water pump? I can't get an accurate location from anything online or the manuals I have access to

 

[tpenfield]

You should be able to connect to the engine and reset codes with just the ignition on and not running.

 

[tpenfield]

Also check the connectors to those 2 sensors to be sure they are tight, not corroded, etc.

 

[apisk]

You should be able to connect to the engine and reset codes with just the ignition on and not running.

You are right, it can be cleared without the engine running, but those codes being present aren't preventing the engine from starting. I want to focus the troubleshooting there first because I don't know if my 2 issues are related, or independent of one another (1 being engine dying while driving and 2 being not being able to start).

If the Crankposition Sensor code was thrown when the engine died, and that same sensor could prevent the engine from starting, I want to believe the issues are related and that is the first potential culprit?

@tpenfield do you know where the Crankposition Sensor is located? The cam sensor I know, but CKP I can't identify it for sure I have this diagram but it doesn't actually help with the location https://www.volvopentastore.com/Electronic-Engine-Control/dm/store_id.366--view_id.784931

 

[tpenfield]

I thought the CPS was top portion of the block, just behind the recirculating pump, slightly to the starboard side.

 

[apisk]

I thought the CPS was top portion of the block, just behind the recirculating pump, slightly to the starboard side.

Would you be able to mark where on the diagram below? The one that seems to be location you described but port side is Cam Sensor right?

 

[apisk]

Update: I was able to finally find the location of the crankshaft position sensor, it's on the back of the engine, facing vertically up, it is very hard to see and find but a pic of the location is attached - I unplugged the sensor and replugged it in, engine started right up but pretty rough - I am wondering if the sensor has gone bad?

 

[apisk]

I was just looking through the diagnostics manuals from Diacom, and found the below section which aligns with what I am experiencing - How do I know whether the issue sits with the Crankshaft Sensor or Cam Sensor, when both were flagged in the codes?

 

[tpenfield]

Different spot that I was thinking, but glad you found it.

 

[alldodge]

The way I read it, the motor will start and it's not stalling so the CMP is not lost.

The motor does run but doesn't run very well and with both CMP and CKP codes, I would lean toward the CKP.

Wrote this down from @muc posting on the J model and testing CMP

[[ How to check CMP (cam position sensor) From MUC

The only good method for validating CMP input is to:

1st). Disconnect the CMP sensor connector and measure the 5V reference 1 voltage to a good ground (ground stud).
2nd). Ensure that there is the same voltage between the 5V reference 1 and sensor return #1 at the CMP connector.
3rd). Check the signal wire and ensure that it has continuity from one end to the other and is not shorted to any ground (power ground, sensor return #1 or sensor return #2).
4th). Then check for a CMP signal at the ECM (pin 23) with either an Oscilloscope, a DC Hertz meter or a good AC voltmeter while cranking the engine with the CKP (crankshaft position) sensor disconnected. Having the CKP sensor disconnected prevents the ECM from firing any ignition coils and any fuel injectors.

Gi-J mid year

Mid-year of the –J model engines, a 120 Ohm resistor was added to the engine harness in the 5V Ref #1 circuit leg feeding the trim sensor. This resistor was added to protect the 5V Ref #1 circuit from being shorted to ground by a faulty trim sensor. It looks like a 2 wire connector and is taped to the engine harness near the fuse box. If the trim sensor shorts the 5VRef #1 to ground on engines that don’t have this resistor, the engine will shutdown due to loss of the CKP and CMP sensors. ]]

 

[apisk]

@alldodge let me outline the sequence of events, my initial post was just a data dump so allow me to clean it up. Apologies in advance if there is unnecessary info, but rather give too much than too little:

1. Friday 8/18 I was beached at a local spot where it is common to pull the front end on to the beach, and as the tide came out, I had to use a good amount of the accelerator in reverse to get off the beach (this caused a lot of shaking and vibrating as I tried to get the front end off the beach). The boat drove home no problem, and the next 2 days (Sat 8/19 and Sun 8/20) had no issues at all outside of the engine starting a little rough
2. On Tues 8/22, took the boat out again with no issues, but at low speeds it felt like there was a lot more vibration from the engine and running somewhat rough
3. On Saturday 8/26 I took the boat out, drove it for 5 minutes at low wake speed, then once accelerating up to speed, after about 1 minute the engine cut off and completely shut down as if the lanyard kill switch was pulled, 2 alarms went off, and the engine would not re-start right away
4. I waited a few minutes and the engine re-started, and I drove back home at low speed. As I drove back, I tested pushing it to higher speeds, and as I did that, the coolant temps dropped. Once I let off, the temps rised again. I did this a few times, happened each time
5. Once I got back to the dock, I turned the engine off and tried to re-start it. It would not re-start, instead just cranking but never turning over.
6. Sunday 8/27, the day after, I started the engine in the morning and it fired right up, but ran a little rough so I turned it off. I was not able to re-start it again after attempting a few more times
7. Monday 8/28, I started the engine in the morning and it again fired right up, where I let it run for a little over 10 minutes (which I captured in the Diacom log shared in Post #1). The coolant temps fluctuated even sitting at idle. This is where I saw the 2 codes for the Cam Sensor and Crankshaft Position Sensor from when the engine died 2 days earlier. After the first start, the engine would not start again which I captured in the second Diacom log

At this point there are a few questions

- is there any significance to the coolant temp rising and falling, or can that be ignored?
- It seems both the Crankshaft Position Sensor and Camshaft Position Sensor can cause the engine to be killed mid drive, and also prevent the engine from starting initially
- Is there a reason to focus on one of the above sensors over the other, or are they both potentially at fault?
- If you are familiar with my previous post, I have been having issues with other sensors on the boat, could this just be another instance of that?
- Could the heavy vibration and shaking from getting off the beach the first day have led to an already compromised sensor being thrown off? It doesn't seem likely since I used the boat so much between then and the ultimate issue, but since that day I noticed a difference

 

[tpenfield]

As for the coolant temperature . . . when you are running the engine at idle and the engine is fully warmed, the t-stat may be fairly far open because the coolant flow is slow. An increase of the throttle will immediately cause a drop in the ECT as cooler coolant rushes in . . . as it does the t-stat compensates and the temperature should come back up.

IIRC, you saw a fairly significant fall in temperature. I cannot recall if you have closed cooling (coolant instead of sea water). But if you do, I would make sure the heat exchanger is up to its normal fill level.

Since you are getting some pretty significant codes (crank and cam shaft), I'd focus on those, unless there is something about the Diacom data that tells us otherwise.

 

[apisk]

As for the coolant temperature . . . when you are running the engine at idle and the engine is fully warmed, the t-stat may be fairly far open because the coolant flow is slow. An increase of the throttle will immediately cause a drop in the ECT as cooler coolant rushes in . . . as it does the t-stat compensates and the temperature should come back up.

IIRC, you saw a fairly significant fall in temperature. I cannot recall if you have closed cooling (coolant instead of sea water). But if you do, I would make sure the heat exchanger is up to its normal fill level.

Since you are getting some pretty significant codes (crank and cam shaft), I'd focus on those, unless there is something about the Diacom data that tells us otherwise.

Thanks for that explanation, super helpful to understand the mechanics of it.

I should clarify, which is actually confusing, in my dash gauge it reads as "Coolant Temp" but I do have the sea water cooling and not coolant/heat exchanger, apologies if that changes things, but the gauge for some reason shows that as the reading. Typically it reads in the 150-160 range once its at operating temp, but it dropped down to under 100, which seemed drastic when usually (from memory) it only drops to the 130/140s and then back up. The pin on the gauge dropped to the lowest point it could go

Would the Diacom data show that those sensors are causing the engine to not start? I am not familiar enough with the program to know where to look to see where/if it would show that cause?

 

[tpenfield]

I believe that the crankshaft sensor is mission critical. As I recall . . . on of my vehicles had a bad crankshaft sensor and it would frequently not start. Had to get it towed to the local repair shop.

 

[alldodge]

Being open cooling, the cooling issue may very well be caused by crud caught in the thermostat. The thermostat should keep the stat closed for the most part but higher rpm moves to much water thru so motor gets cool

With it being touch and go with start/no start if it was mine I would replace the CKP sensor

 

[apisk]

Being open cooling, the cooling issue may very well be caused by crud caught in the thermostat. The thermostat should keep the stat closed for the most part but higher rpm moves to much water thru so motor gets cool

With it being touch and go with start/no start if it was mine I would replace the CKP sensor

Thanks, I have a CKP and CMP sensor coming hopefully today/tomorrow. For the CKP sensor, are the tolerances super tight where I need to grease it before installing, with oil, fuel, something else? The other sensors I have changed were just screwed in, so just want to make sure this one is done properly

 

[alldodge]

Could be, I always like to put a little oil or grease before installing on O ring