Volvo engine random shutdowns | The Tugnuts
Jun. 05, 2025
Volvo engine random shutdowns | The Tugnuts
Hi,
On our R-29CB (Volvo D4-320 diesel engine), for the past couple months, we've been having a problem with our engine shutting down while we are running. Its not completely random, as we have noticed some patterns, but sometimes it is. What happens is that the 10A circuit breaker on the engine trips, and therefore the engine computer goes offline, at which point the Volvo panel at the helm shows an error ["Communication Failure - Communication fault with Engine Management System"] and the engine has shut itself down. Here is the pattern we have noticed - when we are running at low speeds (below RPM) we have never seen this issue. When we accelerate to higher speeds (RPM), it sometimes will happen around -RPM without anything else going on. When we are running at RPM or higher, this will reliably happen when we use the coffee maker or microwave. The parallel switch is in the OFF position, so it surprises me that the house circuit will have any impact on the operation of the engine, but that is what we see.
Until this morning, we have avoided this issue by running the generator, as our experience has been that as long as we run the generator, this issue does not manifest. Historically we rarely used the generator because the house bank was enough for us as we ended most days at a marina. This morning, after anchoring out, we started the generator, and then got underway after raising anchor. After a few minutes, when the engine was warm, we accelerated to our fast cruise speed ... and the engine cut out. This is the first time it happened while the generator was active and engaged (it stayed on throughout). We raised the hatch, reset the breaker, cycled the Volvo ignition, and everything came back online as normal (which is our typical procedure - we are getting good at this). However, the fact that this happened this morning has me worried because we thought we were aware of the conditions which trigger this issue and thereby could manage the boat to avoid this happening while underway. Apparently not!
What I think happened this morning is that the generator was charging the batteries (our new Victron battery monitor showed ~50Amps going into the house bank), and perhaps with that "load" in the sytem, somehow the issue was triggered. Strange, but I don't have a better explanation.
We discussed this with our dealer and several technicians, and no luck in solving it thus far. We checked the wiring and the batteries (the ones we could get to) and things seemed ok. The load tests seemed to indicate the batteries were good but we could not isolate all the individual house batteries nor could we get to the engine battery. We replaced the breaker, but same behavior. The engine has always started fine and seems to hold a charge. Same with the house bank. We have tested the thruster/generator battery and that checks out fine.
Some additional information - the very first time this happened, we had anchored out two nights in a row, which was rare for us and therefore we failed to pay close attentiont to the battery levels that morning. The engine started fine, but we were getting low engine voltage warnings on the Volvo & Garmin systems sporadically throughout the day. After the first warning, I tried to start the generator but the generator battery was too low and didn't start. We ran successfully most of the day and I figured the alternator would put some charge into the batteries and that we would be able to get to our destination. Well, late in the day, we had our first engine shutdown. We didn't realize it at the time but it was the Volvo circuit breaker on the engine, and it likely happened when we made an afternoon tea using the Keurig machine. We got towed back to marina and started the process of working with mechanics to figure out what was/is going on. We have not yet confirmed why this is happening and haven't successfully resolved it. Wanted to see if the folks at the factory or anyone else has seen this and has any advice. Planning to change the batteries just to rule out that possibility but would prefer to have a good explanation of why this happening and how to confirm the failure mechanism, just to know that we are solving the real issue! Is this happening to anyone else?
Regards,
-Darryl Quick update to provide more details and answer questions thus far ...
- we did have a marine tech from AquaYacht check the alternator and seemed to be fine
- inverter is basically always on and seems to work fine; we have 4x 110AH batteries in our house bank so a decent sized (for us) which has supported the use of coffee maker or microwave while running (or at anchor) for over 9 months on the Loop without issue; we generally only use the AC when on shore power at a marina, never from the inverter (probably trips a circuit breaker), and extremely seldom from the generator. In fact we rarely used the generator before this issue.
- in terms of the actual failure, we have to reset the circuit breaker on the engine block, so its not a computer alarm (to my knowledge, as the circuit breaker isn't likely that smart); so my assumption is that there is a voltage/amp spike on the engine circuit which exceeds the threshold of that breaker and causes it to physically trip; once tripped, the engine is offline and the volvo system responds accordingly with various alarms.
- just did a test with the generator off and parallel switch ON and saw the same behavior - engine cuts out at higher RPMs when using the coffee maker. saw a voltage sag down to 12.4v or so on the battery monitor and 100amp draw from the house bank, but I believe that is normal when under load (will do some more tests at rest and confirm).
- tried to load test the batteries but so difficult to get to them, especially without my tools for cutting holes in the floor under the cockpit frig! planning a boat project to get better access to the batteries; thus far only able to load test a couple house bank batteries, but couldn't get to the others (especially the engine battery) so haven't yet load tested it.
- will look for the ACR indicator lights just to verify but I think those are working normally.
- to add more to the puzzle, we found out over the last couple days that even with the generator ON and *no loads*, the engine will shut down at speeds of RPM and above, when the house bank is below 90% soc. We have to run below RPM and keep the generator on until the house bank gets charged back up to 90~95% SOC (at which point the charger starts tapering the amps put into the house bank). Then everything is fine and we can run fast again, but at lower SOC in the house bank, engine cut outs still occur in spite of the generator engaged and no loads
On our R-29CB (Volvo D4-320 diesel engine), for the past couple months, we've been having a problem with our engine shutting down while we are running. Its not completely random, as we have noticed some patterns, but sometimes it is. What happens is that the 10A circuit breaker on the engine trips, and therefore the engine computer goes offline, at which point the Volvo panel at the helm shows an error ["Communication Failure - Communication fault with Engine Management System"] and the engine has shut itself down. Here is the pattern we have noticed - when we are running at low speeds (below RPM) we have never seen this issue. When we accelerate to higher speeds (RPM), it sometimes will happen around -RPM without anything else going on. When we are running at RPM or higher, this will reliably happen when we use the coffee maker or microwave. The parallel switch is in the OFF position, so it surprises me that the house circuit will have any impact on the operation of the engine, but that is what we see.
Until this morning, we have avoided this issue by running the generator, as our experience has been that as long as we run the generator, this issue does not manifest. Historically we rarely used the generator because the house bank was enough for us as we ended most days at a marina. This morning, after anchoring out, we started the generator, and then got underway after raising anchor. After a few minutes, when the engine was warm, we accelerated to our fast cruise speed ... and the engine cut out. This is the first time it happened while the generator was active and engaged (it stayed on throughout). We raised the hatch, reset the breaker, cycled the Volvo ignition, and everything came back online as normal (which is our typical procedure - we are getting good at this). However, the fact that this happened this morning has me worried because we thought we were aware of the conditions which trigger this issue and thereby could manage the boat to avoid this happening while underway. Apparently not!
What I think happened this morning is that the generator was charging the batteries (our new Victron battery monitor showed ~50Amps going into the house bank), and perhaps with that "load" in the sytem, somehow the issue was triggered. Strange, but I don't have a better explanation.
We discussed this with our dealer and several technicians, and no luck in solving it thus far. We checked the wiring and the batteries (the ones we could get to) and things seemed ok. The load tests seemed to indicate the batteries were good but we could not isolate all the individual house batteries nor could we get to the engine battery. We replaced the breaker, but same behavior. The engine has always started fine and seems to hold a charge. Same with the house bank. We have tested the thruster/generator battery and that checks out fine.
Some additional information - the very first time this happened, we had anchored out two nights in a row, which was rare for us and therefore we failed to pay close attentiont to the battery levels that morning. The engine started fine, but we were getting low engine voltage warnings on the Volvo & Garmin systems sporadically throughout the day. After the first warning, I tried to start the generator but the generator battery was too low and didn't start. We ran successfully most of the day and I figured the alternator would put some charge into the batteries and that we would be able to get to our destination. Well, late in the day, we had our first engine shutdown. We didn't realize it at the time but it was the Volvo circuit breaker on the engine, and it likely happened when we made an afternoon tea using the Keurig machine. We got towed back to marina and started the process of working with mechanics to figure out what was/is going on. We have not yet confirmed why this is happening and haven't successfully resolved it. Wanted to see if the folks at the factory or anyone else has seen this and has any advice. Planning to change the batteries just to rule out that possibility but would prefer to have a good explanation of why this happening and how to confirm the failure mechanism, just to know that we are solving the real issue! Is this happening to anyone else?
Regards,
-Darryl Quick update to provide more details and answer questions thus far ...
- we did have a marine tech from AquaYacht check the alternator and seemed to be fine
- inverter is basically always on and seems to work fine; we have 4x 110AH batteries in our house bank so a decent sized (for us) which has supported the use of coffee maker or microwave while running (or at anchor) for over 9 months on the Loop without issue; we generally only use the AC when on shore power at a marina, never from the inverter (probably trips a circuit breaker), and extremely seldom from the generator. In fact we rarely used the generator before this issue.
- in terms of the actual failure, we have to reset the circuit breaker on the engine block, so its not a computer alarm (to my knowledge, as the circuit breaker isn't likely that smart); so my assumption is that there is a voltage/amp spike on the engine circuit which exceeds the threshold of that breaker and causes it to physically trip; once tripped, the engine is offline and the volvo system responds accordingly with various alarms.
- just did a test with the generator off and parallel switch ON and saw the same behavior - engine cuts out at higher RPMs when using the coffee maker. saw a voltage sag down to 12.4v or so on the battery monitor and 100amp draw from the house bank, but I believe that is normal when under load (will do some more tests at rest and confirm).
- tried to load test the batteries but so difficult to get to them, especially without my tools for cutting holes in the floor under the cockpit frig! planning a boat project to get better access to the batteries; thus far only able to load test a couple house bank batteries, but couldn't get to the others (especially the engine battery) so haven't yet load tested it.
- will look for the ACR indicator lights just to verify but I think those are working normally.
- to add more to the puzzle, we found out over the last couple days that even with the generator ON and *no loads*, the engine will shut down at speeds of RPM and above, when the house bank is below 90% soc. We have to run below RPM and keep the generator on until the house bank gets charged back up to 90~95% SOC (at which point the charger starts tapering the amps put into the house bank). Then everything is fine and we can run fast again, but at lower SOC in the house bank, engine cut outs still occur in spite of the generator engaged and no loads
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