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Old 02-10-2020, 09:03   #16
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Re: Yanmar 4JH2E struggles to start

I'd still vote for a connection issue, although it could the starter itself. That you can start reliably with the generator running says that higher voltage from the battery charger compensates for voltage drop in a connection somewhere.

I'd still re-check the major ones, make sure the contact cleaner did its job. On the cable lugs you should see clean copper color (or tin if they are tinned). On the engine clean iron. I find a Scotchbrite scouring pad does a good physical job rather than relying on the chemicals (it could be contacts still wet with cleaner worked OK at your first start, as they dried they became less good). I prefer to use a good, conductive anti-seize paste during re-assembly to keep things working.

As posted above, check the starter mount area:



The negative connection goes through those two bolts in the mount and the face. It's a large surface area so generally OK, but worth a check.

Also check the connections at the solenoid:



Be careful here, the positive from the battery is generally hot all the time, best practice is to disconnect the battery before working on these.

The next steps (to me) depend on how comfortable you are working around the engine while it is moving. Depending on the boat there may or may not be space to do this safely.

You can use a jumper cable (or screwdriver) to jump across the two big contacts on the solenoid shown above (one under the rubber boot and the big copper one). If the engine turns pretty strongly then the problem is likely the solenoid itself. You can also run a test jumper from the battery + to the small connection on the solenoid to bypass the key switch, etc. to rule out that circuit (personally I think this is less likely, but a low voltage on that line can prevent a solenoid from fully pulling in. Usually though that results in the starter spinning but not engaging the Bendix).

After all of that you start to get into connections inside the starter. They're usually pretty easy to check/rebuild, although I see online that third-party they seem to be available for <$100, so....
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Old 02-10-2020, 09:44   #17
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Re: Yanmar 4JH2E struggles to start

I've been lurking for many years but I just had to post a reply so finally registered. Not as painful as I thought it would be lol.

I had the same problem with my 3JH4E two weeks ago. Well there were other issues as well starting with my AC battery charger failing to switch to trickle mode and fried all 3 batteries. When I installed a new cranking battery, I got a weak cranking, not even a full revolution. Attached a booster and no change really. Cleaned every possible connection and no-go. I even pulled the battery selector switch and cleaned those connections, which appeared fine and was getting the low oil beep so assumed those connection were ok.

After many hours and uttering every 4 letter word known to man I pulled the battery selector switch again and hot wired the #1 connection and she fired right up. Not just once but several times. Somehow the switch was ok sending enough juice to the low oil warning but something was preventing a robust connection.

Give it a shot and if it doesn't work I can send you that list of 4 letter words maybe you are missing some.

Good luck.
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Old 02-10-2020, 12:30   #18
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Re: Yanmar 4JH2E struggles to start

I took a Diesel engine maintenance / repair course and learned two key things:
(1) In troubleshooting pick the most likely suspect and either find the issue or COMPLETELY eliminate it as a cause.
(2) In checking electrical issues, ensure you are verifying every bit of the circuit.
I was trying to find a fault in the starter motor circuit and was measuring the resistance by going from wire to wire. Each wire showed 0 ohms, however I was not measuring the resistance between the connection post of a wire to the actual wire (bypassing the wire to the ring terminal and terminal to the post). This is where corrosion typically lurks. Measure the voltage drop at the starter motor when cranking. If the voltage drop is greater than 0.5 volts you need to find the source of the voltage drop. You can eliminate much of the start circuitry by hot jumping between the starter solenoid and the starter motor. Look at a few Youtube videos on "slow crank to start". Here's a good one to get started
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Old 02-10-2020, 12:50   #19
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Re: Yanmar 4JH2E struggles to start

I took a Diesel engine maintenance / repair course and learned two key things:
(1) In troubleshooting pick the most likely suspect and either find the issue or COMPLETELY eliminate it as a cause.
(2) In checking electrical issues, ensure you are verifying every bit of the circuit.
I was trying to find a fault in the starter motor circuit and was measuring the resistance by going from wire to wire. Each wire showed 0 ohms, however I was not measuring the resistance between the connection post of a wire to the actual wire (bypassing the wire to the ring terminal and terminal to the post). This is where corrosion typically lurks. Measure the voltage drop at the starter motor when cranking. If the voltage drop is greater than 0.5 volts you need to find the source of the voltage drop. You can eliminate much of the start circuitry by hot jumping between the starter solenoid and the starter motor. Look at a few Youtube videos on "slow crank to start". Here's a good one to get started
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Old 02-10-2020, 17:33   #20
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Re: Yanmar 4JH2E struggles to start

Yes. The older Yanmars did have problems with the wiring looms and the instrument panels. You may wish to consider replacing or updating the lot. Lots of good advice above. Any good auto electrician can rebuild the entire loom using heavier duty tinned wiring (and probably reduce the overall length if possible) and overhaul the instrument panel. The switching system to start up at the panel (the keyed switch and the press button) plus the light wiring to the starter solenoid are very common villains in the crime.
Voltage testing along the loom is usually very informative but a simpler, faster, less reliable method is temperature testing. If a terminal gets hot (or even warm) during starting attempts then it is suspect. Not foolproof.
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Old 03-10-2020, 15:28   #21
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Re: Yanmar 4JH2E struggles to start

Well you guys are gonna hate me...

I spent another 3+ hours troubleshooting this today. Took apart every connection I could find. Sanded down the leads, sprayed with the electronics cleaner, tightened it all down real pretty. Shorted the starter solenoid. Nothing was working. I start in with the multimeter looking for voltage drop issues, and I'm getting readings that make no sense.

Finally I'm tracing the cable from the positive battery lead to the solenoid and discover... The battery I'm tracing is actually part of my house bank, just separated into a separate compartment... Whoops!

Turns out the PO had told me incorrectly that I had separate batteries for starting the genset and the main diesel. When I initially replaced the battery, I tried to make sure I had pulled the right one by starting the genset after disconnecting the battery. It worked fine, so I figured the one I disconnected was the right one for the Yanmar :P

In reality the genset and Yanmar start off the same battery. I swapped the new battery for the correct old starter batter, and what do you know? It starts up no problem now! My first theory was right the whole time, I just swapped the wrong battery like an idiot!

Thanks for all the help with my dumb problem everyone! At least now I have shiny tight clean connections everywhere
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Old 03-10-2020, 15:46   #22
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Re: Yanmar 4JH2E struggles to start

Thanks for the update - no problem starting is a good outcome!

And now you know your boat's starting circuit so much better!
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Old 03-10-2020, 16:43   #23
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Re: Yanmar 4JH2E struggles to start

Quote:
Originally Posted by JebLostInSpace View Post
Well you guys are gonna hate me...

I spent another 3+ hours troubleshooting this today. Took apart every connection I could find. Sanded down the leads, sprayed with the electronics cleaner, tightened it all down real pretty. Shorted the starter solenoid. Nothing was working. I start in with the multimeter looking for voltage drop issues, and I'm getting readings that make no sense.

Finally I'm tracing the cable from the positive battery lead to the solenoid and discover... The battery I'm tracing is actually part of my house bank, just separated into a separate compartment... Whoops!

Turns out the PO had told me incorrectly that I had separate batteries for starting the genset and the main diesel. When I initially replaced the battery, I tried to make sure I had pulled the right one by starting the genset after disconnecting the battery. It worked fine, so I figured the one I disconnected was the right one for the Yanmar :P

In reality the genset and Yanmar start off the same battery. I swapped the new battery for the correct old starter batter, and what do you know? It starts up no problem now! My first theory was right the whole time, I just swapped the wrong battery like an idiot!

Thanks for all the help with my dumb problem everyone! At least now I have shiny tight clean connections everywhere

Break out the beers.
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