Island Time 1,313 Posted August 6, 2020 Share Posted August 6, 2020 Looks and sounds like a sticking valve - sometimes a valve not completely sealing and blowing out compression via the intake system. When the tech got it to drop to 2 cylinders it was the same regardless of the cylinder stopped? Be interesting to see what volvo say... Quote Link to post Share on other sites
Neil C 1 Posted August 6, 2020 Share Posted August 6, 2020 An intermittent fault in the MDI 'black box' affecting the fuel stop solenoid ? Quote Link to post Share on other sites
DrWatson 382 Posted August 6, 2020 Author Share Posted August 6, 2020 I’m starting to think we should run a poll,... 1 Quote Link to post Share on other sites
DrWatson 382 Posted August 6, 2020 Author Share Posted August 6, 2020 10 hours ago, Island Time said: Looks and sounds like a sticking valve - sometimes a valve not completely sealing and blowing out compression via the intake system. When the tech got it to drop to 2 cylinders it was the same regardless of the cylinder stopped? Be interesting to see what volvo say... It dropped down the same regardless of the cylinder. But it didn’t make that kick. Quote Link to post Share on other sites
marinheiro 365 Posted August 6, 2020 Share Posted August 6, 2020 one other left field possibility to check, because I had this happen to me - a faulty alternator. In my powerboat days with a big Perkins had the situation where the engine was trying to jump off its mounts when warm. Zeroed it down to the alternator and on 3rd visit to the auto leccy insisted they open it up and they found one of output wires had come loose and was intermittently disconnecting. Quote Link to post Share on other sites
Fogg 427 Posted August 7, 2020 Share Posted August 7, 2020 12 hours ago, DrWatson said: I’m starting to think we should run a poll,... Haha! I think you’re right the honest answer is that we’re all pretty clueless and hopeless and helping you aren’t we? Be v interesting to see what the verdict is. Quote Link to post Share on other sites
Island Time 1,313 Posted August 7, 2020 Share Posted August 7, 2020 If it does not do it down a cylinder, what happens if you remove the air cleaner? Quote Link to post Share on other sites
DrWatson 382 Posted August 7, 2020 Author Share Posted August 7, 2020 haha, well I don't think "Hopeless at helping" is accurate but we might soon be exhausting our reservoir of explanations. The breadth of experience here on the forum is exceptional, and each suggestion has been based on a member's previous experience. Some of those experiences include the strangest things which others of us would never have considered, but the suggestions are made on first hand examples, and all made with reason. It's not like people To date: Buggered injector pump/buggered injector (not being a mechanic this was my first guess) Burnt or sticking valve Broken crank Obstruction on the prop Broken engine mount Broken/occluded cam Alternator Wiring loom issue (Lordy I hope not, there's about 2km of wiring on this boat) Black box Clutch cone grabbing Oil level in gearbox Morse cable adjustment Engine drive plate Starter motor/flywheel Engine dampner plate One thing to consider is that it only happens when the whole set up is warm and restarted... (might happen when it's warm immediately, but I normally don't leave it running in neutral after I've finished motoring somewhere.) It also didn't do it earlier in the trip when we ran the motor in Neutral for 40 min or so to charge batteries while making water - so when the motor is warm and the gearbox not. So it's intermittent and very regular... about once every 12th revolution (Thanks JimS for counting), so it's likely to be geared issue, but not something related to the engine firing or engine timing itself? I'm guessing a sticking valve would not occur "exactly" every 6th action. 8 minutes ago, Island Time said: If it does not do it down a cylinder, what happens if you remove the air cleaner? haven't tried... Quote Link to post Share on other sites
jim s 34 Posted August 7, 2020 Share Posted August 7, 2020 The sail drive is 2.3 : 1 or thereabouts so that becomes less likely. a warm engine will react to (ignite) a stray amount of fuel much more readily than a cold engine. Pity you aren't in NZ we could have a Crew barbeque with a sweepstake while we sort it... Quote Link to post Share on other sites
DrWatson 382 Posted August 7, 2020 Author Share Posted August 7, 2020 18 minutes ago, jim s said: The sail drive is 2.3 : 1 or thereabouts so that becomes less likely. a warm engine will react to (ignite) a stray amount of fuel much more readily than a cold engine. Pity you aren't in NZ we could have a Crew barbeque with a sweepstake while we sort it... Hahah, we could still do the sweepstake, and the winner gets to sail Firefly to Jersey and back to France at the end of October... She needs to leave the EU for at least a night, and what with various quarantines and work commitments, I'm not sure it's gonna work out. Quote Link to post Share on other sites
Steve Pope 255 Posted August 7, 2020 Share Posted August 7, 2020 12 revs 3 x cylinders, so 1 cylinder / piston, valve, cam lobe, not a lot of clearance between the piston and cylinderhead at tdc.??? I hadn't realised that it showed only when hot, another dimension. Quote Link to post Share on other sites
Cantab 341 Posted August 7, 2020 Share Posted August 7, 2020 If you put it in gear, while its doing the knock, does it keep doing it? Or has it ever done it while in gear? Quote Link to post Share on other sites
wheels 544 Posted August 7, 2020 Share Posted August 7, 2020 And hence why I am saying it is not engine. It is far too regular, yet outside anything that is cyclic on the engine. Engine faults are going to be either random or if regular, will have much higher repetition frequency to coincide with engine RPM. This fault is regular as stated at about every 12th rotation, but far too far apart repetition rate to be anything engine related. Only problem is, the Gearbox and sail drive is all geared far to fast for this as well. Thought. Do you have an Alternator charge controller? Could something be electrically timed that it loads up ALT momentary and then trips out due to a fault and keeps trying to automatically reload again. How about a fridge compressor doing the same? What ever the fault is, it seems to be timed to switch in and then trips out again every couple of seconds. Quote Link to post Share on other sites
mattm 106 Posted August 7, 2020 Share Posted August 7, 2020 I doubt it will be an alternator issue. Testing alternators with external regs sometimes requires briefly full fielding the alternator, they don’t kick anything like that, not even on a single cylinder 10hp running at lower revs. Same for the fridge compressor, the go off to full on instantly on every engine that has one and this isn’t the result. Quote Link to post Share on other sites
jim s 34 Posted August 7, 2020 Share Posted August 7, 2020 There are ways the engine could cause this problem - and i certainly don't know many of them but one possibility is the case hardening on one of the camshaft's injector lobes failing and contaminating the roller and pin that actuate the actual injector - causing it to "run over a lump" (firing its cylinder early ) which would happen at a rate according to their relative diameters . Certainly left field but occasionally even an airliner falls out of the sky with some obscure left field fault. Quote Link to post Share on other sites
Fish 0 Posted August 7, 2020 Share Posted August 7, 2020 The suspense is killing me. I really hope you sort this out soon Dr, following this thread is like watching a thriller movie that never gets to the final scene... 1 Quote Link to post Share on other sites
Steve Pope 255 Posted August 8, 2020 Share Posted August 8, 2020 I would doubt that you are the first Wolwo owner to have that problem, Big companies are often slow off the mark with things that can / have come back to bite them. A bit of perhaps, superfluous information, the Wolwo D-30 is a marinised Perkins 403D -11, as used in generators, small diggers, etc. etc. Quote Link to post Share on other sites
Fogg 427 Posted August 8, 2020 Share Posted August 8, 2020 Have you got a holding tank? Could it blocked? Maybe every 14.3 engine rotations it tries to clear a stubborn blockage and gets a blowback? 1 Quote Link to post Share on other sites
wheels 544 Posted August 8, 2020 Share Posted August 8, 2020 Hahaha, good one Aleana. 😁👍 Quote Link to post Share on other sites
Fogg 427 Posted August 9, 2020 Share Posted August 9, 2020 Maybe you’ve got Covid-diesel bug and it’s coughing? You are in a hotspot in Europe after all. Do you think Volvo have considered this? Quote Link to post Share on other sites
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