Volvo Penta Marine Diesel Engines
About my Volvo Penta marine diesel engines issue. This tale is from my own boat. I bought the boat more than 2 years ago and have recently completed a total refit. The engine is a 50hp Volvo MD22 which is a Perkins with green paint, and it has just 600 hours on the clock. It is also unusual in that the engine has an insulated or isolated return electrical system which is normal when installed on metal hulled boats but not on my FRP one. It makes no difference and I would prefer this type anyway although it does change the electrical philosophy.
I have regularly run the engine up to temperature and under load and all has operated normally. I had noticed an abnormal clicking start relay when starting and hadn’t pursued the cause at this stage. Then following events resulted in a steep learning curve about the engine and it was the start of the proverbial chase down the rabbit hole
My Boat Starting System Problem
One sunny day I decided to do my regular engine start and run. I was greeted with an ominous <Click Click> of the solenoid but no turning over of the engine or any starter motor rotation. That is a classic low start battery voltage symptom. For the record a single click usually indicates a bad starter motor solenoid, rapid multiple clicks often indicate a low battery voltage and no click at all indicate no electrical power or a seized engine. I did a check with my multimeter and it was indeed low, and that turned out to be due to a wiring issue on the shore powered battery charger and it wasn’t charging correctly, and all down to my own omission.
Volvo Penta Marine Diesel Engines
With the battery voltage issue resolved the next start attempt, with the ominous <Click Click>. WTF was my exclamation and once more down to the engine bay to investigate. I did a touch test of the solenoid and starter motor terminals, and they were quite hot even though the start attempt was just for 2-3 seconds. Not a promising symptom. Naturally I assumed I had a high resistance terminal and so I took out the starter motor. A good exercise for the future as well. The starter motor main terminal on the start solenoid was a brass one and at some stage the previous owner had damaged or cross threaded the nut and stripped off several threads so the terminal nut could not be properly torqued. This of course creates higher resistance and generates heat. The solenoid is no longer available and the start motor turned out to be made by Lucas CAV and the solenoid was Italian Magneto Marelli. The solenoid main contact resistance was checked with a multimeter just to confirm it was good, as some tend to jam or weld together and end up with relatively high resistance. The starter motor will be repaired and the damaged terminal replaced. Read more about engines in my book The Marine Electrical and Electronics Bible 4th Edition.
My Boat Starting System Problem
I had as part of my own redundancy and
contingency planning I had invested in a replacement starter motor at
considerable expense. So without further delay I installed it. With the starter motor issue resolved the
next start attempt, with the same ominous <Click Click>. Extra big neon WTF!
At this juncture I started tracing through everything in the control wiring and
discovered several deficiencies. The control relays for stop and preheat were
under rated and these were replaced. On this isolated return electrical system engine
there is a 55A ground fault fuse and on investigation was found to have been blown
and had been for a very long period. After some research online I found out
that no other wiring should be connected to the engine block which bypasses the
grounding circuit. This provides an engine ground circuit for glow plug and
stop solenoid operation. The previous owner had connected on bonding cables to
the engine block which caused the short. So, with fuse and relays replaced and
engine check for any illegal connections time to restart. Lesson, read you Volvo Penta marine diesel engines Instruction book and get a copy of the service manual.
My Boat Starting System Problem
With the wiring and fuses issues resolved the next start attempt, with the same ominous <Click Click>. More WTF! The thought had dawned on me that the engine had some how become seized, the worst case scenario. The electrical starter motor has to overcome the starting resistance torque which is the friction resistance torque, inertia moment, and compression resistance torque of the piston. When a starter initially turns over there is a large current spike as the initial inertia is overcome. This can be up to an instantaneous and very short duration inrush current spike of 200 amps up to a 1000-amps as the starter motor has to generate high torque to overcome the engine inertia.
My Volvo Penta Marine Diesel Engines Problem
Now a quick check of exhaust muffler and water trap ruled out Hydro Lock of the engine. While investigating this the Vetus muffler has an integral non return flap valve which is good to know. But I inadvertently discovered a small series of pinhole water leaks on the discharge side of the muffler. A small crack in the elbow existing since the engine was installed 25 years ago was the source of my constant but unexplainable bilge water. See the images and that is all good now.
My Boat Starting System Problem
What can cause a diesel engine to seize? After years at sea as a marine engineer I was always ready for the unexpected but this was baffling. The only remaining causes were the transmission, or a situation where a piston is stuck at TDC and the engine is mechanically locked. Lubrication issues on bearings and pistons can create seizure issues but were discounted. Overheating wasn’t an issue either. Given the engine was running the week before without any signs of problems and shut down normally, mechanical issues were largely excluded. Corrosion in cylinders causing seizure was ruled out as the engine is run regularly.
My Boat Starting System Problem
Next check was the status of timing belt
and this was found to be okay. The
theory that a piston was jammed at TDC was a possibility and some damage was
preventing or locking the crankshaft. I phoned the local Volvo service people
and they said the technician would call back to discuss. I put the engine in
gear and then using a wrench rocked the prop shaft back and forward and the
engine started. It is hard to turn over the crankshaft by hand on this engine. Since
then the engine has started many times and performed flawlessly and the real
and actual cause is still unclear. Two
weeks later I got a call from the local Volvo service technician. I described
the symptoms and he said that it must be the battery voltage, No, fully charged
and almost new! The starter motor must
be at fault. No, and I bought a new one from your company just weeks ago, works
fine. He said it must be Hydro locked then, you will need a rebuild or new
engine! No that would be impossible in my configuration. He didn’t believe me. I
then asked him about pistons being stuck at TDC and so on and he just dismissed
this out of hand. Only then did I describe the fix and he just muttered about
no longer an issue and hung up the phone. So clearly he didn’t have much in
depth knowledge. I guess I won’t call him again. So as always you wonder and
wait for a repeat of this but so far none has come. At least all the other hidden
issues were identified and resolved and I know a lot more about this particular issue. Volvo Penta marine diesel engines are still great engines.