Yanmar 4JH2E ring gear (flywheel)

[Tacomasailor]

Our sailboat is powered by a 1994 Yanmar 4JH2E with 2880 hours on it. We have owned the boat since new. The engine runs flawlessly and starts in an instant if the starter spins.

At times, when I turn the key, I just get a click from the solenoid and the voltage on the 12V lead to the solenoid drops from 13.8V to 8.8V. The click and no starter spin began occurring, very infrequently about 100-engine hours ago, prior to replacing the starter/solenoid and key switch and has become more frequent in the last 18-months.

I made a small jumper with a switch in it to connect the battery lead to the solenoid lead (a safer version of the screwdriver trick). I get the same result when I turn on the switch: Ten times in a row the starter spins the engine. Then I get the “click” and no starter spin. That might happen just once or several times in a row. Eventually, the starter spins when I re-activate the switch.

In the last year, as a matter of preventative maintenance, I have installed (20-engine hours ago) a new OEM starter and solenoid, B-panel key switch, cleaned all starter circuit connections, and put new ring connectors on all wires. I have verified 0 (zero) ohms resistance in all the wiring from the key to both leads on the solenoid. The problem is now occurring quite frequently.

I imagine the problem is a bad tooth, or tooth with a burr, on the flywheel (ring gear in Yanmar terminology). The starter pinion gear hits the burr and can’t advance, thus the starter motor can’t be energized.

A common problem in the older cars I have worked on!

I have to remove the Yanmar alternator, exhaust elbow, and exhaust manifold (heat exchanger) to get to the starter and flywheel. I do not want to bother with all that work if there is little likelihood of being able to fix the bad tooth.

QUESTION:

Has anyone bothered to remove the starter from their Yanmar and mechanically rotate the engine while trying to find the bad tooth or burr?

Did you successfully smooth the tooth or burr?

Any other comments on the cause of the problem?

 

[LarryM]

That does not sound so good. To troubleshoot this, I would be tempted to rotate the starter as you have done in the past until it stops/jams. Let the engine sit for a while to bleed off any pressure in the cylinders, then remove the starter. You should be able to see the actual gears that were engaging at the time it locked up. There may be other areas on the ring gear, but this will identify one of them positively so you can get some idea of what is failing.

Fortunately, in the 4JH2E, the starter ring gear p/n 124550-21600 is replaceable without replacing the flywheel, and is not that expensive. The labor to replace it, however, could be another matter.

Hopefully it is a burr that can be dressed down by hand with a file or something easy like that.

BTW, if you are going to turn the engine by hand to examine the entire ring gear, be sure to pull the stop control if manual, or crack the injector nuts to prevent the engine from starting. The JH diesels start very easily and will run with the ignition turned off!

 

[Ski in NC]

Try this: When starter clicks but no worky, put a wrench on crankshaft nut and turn engine a touch. That will expose a fresh part of the ring gear. See if that fixes it.

If starter clicks but does not rotate, something is wrong for it to draw volts down to 8.8. Put a meter right on starter pos lug and gnd and see what volts go down to.

 

[ddalme]

Sounds like a bad ground with the voltage drop on a new starter. Normally you would smoke the starter if engaged and stuck.

 

[BryanF]

I would also check your battery. When I see any battery drawing down below 10 volts on start up I want to load test the batteries. And in my experience the age of the batteries is not a consideration. Dead cells happen in all ages of batteries.

 

[RickB]

I would also check your battery.

Best call so far.

First thing to check ... is the voltage at the battery terminals really down when this happens? Check on the post itself, not the cable terminal.

What is the condition of the battery cable connections on the battery posts? Have they been off and cleaned lately? Are they tight?

I made a small jumper with a switch in it to connect the battery lead to the solenoid lead (a safer version of the screwdriver trick).

It's not the equivalent. All you are doing is bypassing the switch. The "screwdriver trick" bypasses the solenoid and switch wiring and puts battery power directly to the starter motor. That is why it sparks so much, there is a lot of power available if the battery cables and connections are in good shape.

Ring gear issues tend be noisy and don't cure themselves after resting for a bit.

 

[Tacomasailor]

More data

Thanks for all the replies

Batteries: 675 amp hours being charged at 14.3V by 500 watts of solar panels while the starter tests are being conducted. I can crank on the engine for 10-seconds at a time, with the fuel stop pulled, as many times as I want with no reduction in starter spin speed. I do this with a voltmeter from the starter battery cable + and engine ground. Voltage drops to about 12.4 while spinning but immediately returns to 13.9 or higher.

Cables: 1/0 36" long to batteries. New connectors on starter and engine ground.

Connections: I removed all cables and connectors from both ground and + at engine and starter. Cleaned to fresh copper and reseated connectors and nuts. I then cleaned both connections on the battery side and retightened the battery clamp nuts.

I measure exactly the same voltage at the batteries as I do between the + cable and the starter frame (ground).

I measure less than 1 ohm resistance between starter frame and battery ground and starter + and battery +.

When the solenoid clunks but the starter does not spin - I manually rotate the engine a couple teeth on the ring gear and every single time the starter spins on the next key turn or switch flip. I have done that hundreds of times and it never fails - the starter always spins the first time I activate it after manually rotating the engine.

19mm socket on nut on fan belt pulley mounting bolt and 2' breaker bar with engine fuel shutoff. It is very easy to rotate my little 4-cylinder 50 HP engine by hand.

 

[Tacomasailor]

Yanmar service manual

The Yanmar 4JH2 engine series says "replace the ring gear when the starter pinion fails to engage the ring gear"

My reading of the very detailed starter solenoid drawing is that the heavy 12V circuit to the starter motor is not engaged until the pinion gear has moved forward several mm to engage the ring gear.

The teeth on the pinion gear and the starter are beveled to allow them to slide past each other while a torsion spring rotates the pinion gear to ease it onto the ring gear.

If the pinion gear can not move far enough the starter motor will not spin because the "moveable contactor" does not meet the "stationary contactor" thus completing the high amperage 12V circuit from the battery to the starter motor .

Has anyone else spent any detail time with the Yanmar manual or Hitachi Starter manual?

 

[FF]

Most starters will have the shaft that throws the pinion with a machined twist .

This is to be sure the unit engages, as it slides fwd.

Perhaps a bit of lubricant on the shaft that slides the pinion will do it.

 

[RickB]

Most starters will have the shaft that throws the pinion with a machined twist .

This is to be sure the unit engages, as it slides fwd.

Perhaps a bit of lubricant on the shaft that slides the pinion will do it.

Given the latest information that is a good idea.

 

[LarryM]

Given the latest information that is a good idea.

+1

 

[Ski in NC]

Note also that 4cyl 4strokes stop in one of two places when shut down, 180deg apart. So it is possible for there to be a worn spot in ring gear.

 

[Tacomasailor]

OK - thanks for the great responses.

That is interesting news about the engine stopping in only one of two locations. It sounds like I do have to spend the four hours to get to the point I can check the teeth on the ring gear.

 

[BryanF]

OK - thanks for the great responses.

That is interesting news about the engine stopping in only one of two locations. It sounds like I do have to spend the four hours to get to the point I can check the teeth on the ring gear.

Sadly, that is the next step now that you have verified all the other parts of the system are working as they should. Once you pull the starter you should be able to rotate the engine by hand and look at the ring gear teeth as they go by. Major damage will be easy to see- tooth wear less easy to see if you can not get a good look. It would probably be worthwhile to have the starter checked out by a starter shop but I suspect that you are on the right track in suspecting a ring gear problem.

 

[Ski in NC]

Most starters also have a circuit that the solenoid "pull in" coil actually goes through the motor. So as solenoid pulls the gear in, motor gets some current and rotates some. This feature and others usually prevents gear jamming. This is also why if brushes are not making good contact, solenoid will not pull in at all.

Have you already replaced starter once?