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11-07-2020, 11:35
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#1
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Registered User
Join Date: Jul 2012
Location: Tampa Bay, FL
Posts: 29
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Yanmar 3YM30AE diesel engine electrical issue
Hi All,
Looking for suggestions to help diagnose the problem. Engine is 5 years old, approx 500 hours on it. Two related symptoms:
1) Engine control panel powers up normally. But when I hit "glow" button, the panels turns off as if power to panel is completely cut. Panel will turn back on normally with the power button.
2) If instead of using the "glow" button, I just try to start the engine, the panel again immediately turns off in the same way. The engine does not turn over at all.
Checked batteries. They are fine. Connection wire from battery bank to back of starter/solonoid "looks" fine. Its a big job to start taking wires off really checking them, so I thought I would ask for advice first.
Generally speaking, I suspect this is probably due to a bad connection. But why would the control panel turn completely OFF? Do the symptoms provide any clues to which wires might be the problem?
From the service manual, it looks like the main power that feeds the engine and the control panel goes first to either the starter motor or the solonoid on the starter. From there, somehow, it appears to branch both to the yanmar control panel and the relay controlling the glow plugs... But it not really clear if this is one wire or two and where exactly they tie into the starter.
Any other suggested tests I can do to help diagnose? For example - to determine if the problem is the yanmar wiring harness as opposed to the main connection to the battery?
Thanks in advance!
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11-07-2020, 11:42
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#2
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Marine Service Provider
Join Date: Jan 2013
Location: Kimberton,Pa.
Boat: Cabo Rico 34
Posts: 1,031
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Re: Yanmar 3YM30AE diesel engine electrical issue
Check out the very active and knowledgeable Yanmar Marine Engine Owners Group on FB
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11-07-2020, 12:02
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#3
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Registered User
Join Date: Aug 2013
Location: Miami Beach
Boat: Island Packet 38
Posts: 263
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Re: Yanmar 3YM30AE diesel engine electrical issue
You say you "checked batteries" and they are fine. Not clear how they were checked, but batteries can show good voltage but have little or no capacity. A large load like glow plugs or a starter can draw the battery voltage down to near zero (turning the instrument panel off). So the batteries really should be load tested or checked with a hygrometer (if lead acid) to ensure that they really are fine.
If batteries are OK, there is likely a bad connection or component somewhere. I'd start by checking (removing and cleaning) the negative battery connection to the engine block. It's amazing how frequently this is the source of problems. Then check battery terminal connections and connection at the starter solenoid. Since this is triggered by both the solenoid and the glow plug relay it seems likely that the issue is upstream of the starter solenoid (somewhere between the batteries and the starter solenoid).
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11-07-2020, 12:08
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#4
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Moderator
Join Date: Feb 2012
Location: Carrabelle, Florida
Boat: Fiberglas shattering 44' steel trawler
Posts: 6,084
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Re: Yanmar 3YM30AE diesel engine electrical issue
When you turn the key, something is pulling down the voltage available to the panel until it goes out. Ditto when you turn on the glow plugs. One bet would be that while the battery is sitting at 12.8v, it has no capacity and voltage drops like a rock when you turn the switch. You test that with a resistance load tester, $12.50 at Harbor Freight. Second possibility is a corroded or loose connection to the battery. It's fine, but because of the bad connection, only a low current can get through. That used to happen in cars - the lights would be bright, but the starter would not work, because the connection was loose/corroded. The third common cause in my experience is a shorted starter, but that doesn't explain it happening when you turn on the glow plugs.
Most of the time, you track down electrical faults by where 12.8v exists, with a voltmeter. In this case you can't do that, you need to track down where the amperage can't get through to turn your starter and light up your plugs. If you start at the battery, make sure that it is OK, and then clean and tighten each connection, you should find it.
Good luck with it.
__________________
Never let anything mechanical know that you are in a hurry.
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12-07-2020, 06:53
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#5
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Registered User
Join Date: Jul 2012
Location: Tampa Bay, FL
Posts: 29
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Re: Yanmar 3YM30AE diesel engine electrical issue
Great suggestions. Will check out the FB group mentioned.
In lieu of load testing the battery, I set a volt meter on the battery terminal and watched the voltage (12.84 V) while I attempted to power the glow-plugs. It dropped to 12.82 V but no further. A proper load test would be better, I agree.
I didn't mention that I have two battery banks and have the same symptom with each one.
I will try monitoring the battery voltage from the starter and see if there any any drop there. The service manual says the glow-plugs draw 8-10 A, so for 3 of them the current draw is only ~30 amps. That seems a lot less than the 200+ amps the starter would draw.
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12-07-2020, 07:31
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#6
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Re: Yanmar 3YM30AE diesel engine electrical issue
You have a loose connection likely a ground, works fine until you attempt to draw current then because it’s loose / dirty it fails.
If it were the batteries, the voltage would tank, like drop to 6V or something, not a .2V drop.
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12-07-2020, 08:42
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#7
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Registered User
Join Date: Apr 2005
Location: Seabroook Texas or Southern Maine
Boat: Pearson 323, Tayana V42CC
Posts: 1,505
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Re: Yanmar 3YM30AE diesel engine electrical issue
X2 on bad ground/connection.
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12-07-2020, 10:46
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#8
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Registered User
Join Date: Mar 2008
Location: where my little boat is ;-) now Philippines
Boat: Catamaran Schionning Wilderness 1320, built myself
Posts: 475
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Re: Yanmar 3YM30AE diesel engine electrical issue
Had 3GM and now 3ym, 2 different catamarans. My, quite similar issue, engines 2005: battery to engine to panel (starter switch) back to starter solenoid, approx 20m. The voltage drop at the starter solenoid was significant, as for the size of our yacht I had to use the extension harnesses. Solving the problem was easy, I installed a cheap Hella 70A automotive Relais. The starter switch triggers the Relais, this Powers the starter solenoid. Never had a starter problem any more.
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12-07-2020, 12:45
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#9
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Registered User
Join Date: Apr 2016
Location: Back on dirt in Florida
Boat: Currently in between
Posts: 1,338
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Re: Yanmar 3YM30AE diesel engine electrical issue
X3 it is a bad ground. Always check the ground first, easiest to do and 'almost' always the culprit.
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SV Bacchus - Living the good life!
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12-07-2020, 13:15
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#10
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Registered User
Join Date: Sep 2017
Location: Langley, WA
Boat: Nordic 44
Posts: 2,506
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Re: Yanmar 3YM30AE diesel engine electrical issue
Checking the voltage at the battery only tells you that the battery is OK. Watch the voltage at the panel. It will drop significantly when you switch on a heavy load.
I agree with the other posts - you have a loose or corroded connection or a bad wire.
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12-07-2020, 14:18
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#11
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Registered User
Join Date: Nov 2013
Location: Slidell, La.
Boat: Morgan Classic 33
Posts: 2,845
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Re: Yanmar 3YM30AE diesel engine electrical issue
If it were me, given your symptoms, I'd start at the batteries and work from highest amp draw towards lowest. Could be anywhere, but that's what I'd do. Not too likely at only 5 years old, but also check the primary cables themselves for anomalous stiffness, which would indicate internal corrosion.
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12-07-2020, 15:26
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#12
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Registered User
Join Date: Sep 2007
Location: Queensland, Australia
Boat: None at present--between vessels. Ex Piver Loadstar 12.5 metres
Posts: 1,475
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Re: Yanmar 3YM30AE diesel engine electrical issue
Sounds like a bad earth or poor positive battery connection. The glow plug and starter relays are operating, but there is insufficient current getting to the engine.
Sounds like the earth connection--or negative connection--and it could either be in the engine room or on the starting battery terminal. Check ALL connections anyway.
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12-07-2020, 16:46
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#13
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Registered User
Join Date: Mar 2008
Location: where my little boat is ;-) now Philippines
Boat: Catamaran Schionning Wilderness 1320, built myself
Posts: 475
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Re: Yanmar 3YM30AE diesel engine electrical issue
Reading the thread again I cannot read that the solenoid even clicks or the engine makes the smallest movement. Maybe I overlooked that. If this is true it might be a stuck starter solenoid. That will pull tremendous current. A few hammer strokes while starting usually help. Btw, ever since I installed a starter switch in the engine room, just for convenience.
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12-07-2020, 17:04
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#14
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Re: Yanmar 3YM30AE diesel engine electrical issue
No, if you were pulling a huge load, the batteries would drop more than .2V.
A starter battery dropping to 10V is not at all uncommon during starting, of course a large house bank is not going to drop so much, but it would be more than .2V
On edit, I have seen a battery switch do this too, burnt or corroded contacts inside the switch won’t pass current, and act like a loose connection.
Not saying it’s that as that’s not real likely, but once you exhaust all other possibilities try jumping the switch
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13-07-2020, 03:50
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#15
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Registered User
Join Date: Apr 2016
Location: Back on dirt in Florida
Boat: Currently in between
Posts: 1,338
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Re: Yanmar 3YM30AE diesel engine electrical issue
Quote:
Originally Posted by blubaju
Btw, ever since I installed a starter switch in the engine room, just for convenience.
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I have done the same, so much easier for any maintenance requiring engine rotation, i.e. bleeding the lines.
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SV Bacchus - Living the good life!
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