Why to start your engine with the charger OFF (a glow plug question)

Bobg · May 14, 2009, 09:07:27 PM

Hi Guys, well here we go again, last fall my engine wouldn't start unless I fogged it with starting fluid, I know not a good idea, and when I shut the engine off, it would start with no problem after that. I replaced all three glow plugs this winter and done the solenoid upgrade, here is the problem, all 3 new glow plugs failed, I have bench tested them and can't get any heat out of them, the first time I tried to start my engine, it kind of galloped along until it finally started. I did get a voltage drop which got progressively weaker until now there is no voltage drop.

guys I only got one bad start with the new glow plugs, what's going on that I destroy my glow plugs. I have 14 volts to each one, but they just won't heat up, and when I remove them, they are wet with fuel.

I have put a MOM switch in the engine compartment so I know the solenoid is getting voltage to the plugs, I get nothing at the plug until I activate the solenoid, then get 14 volts but no heat.

I have been trying to start while plugged into shore power. I now know that is a no-no, but I do believe since I got the boat and I was real dumb then, that's the way I always started the boat and didn't destroy the plugs for 2 seasons anyway.

in a test, If I put the small threaded end (where the wire goes) on the battery positive, and the the body of the plug (where it enters the engine) on the negative side of the battery, it should heat up right? well none of the 3 new ones heat up. I have read all the posts from the archives and didn't come up with a answer on destroying new glow plugs almost instantly. I will order 3 more new ones, but am understandably nervous about putting them in. Any Ideas? will 14 volts while plugged in to shore power wipe out the plugs right away? could I have gotten 3 new bad ones? Thanks guys Bob

Ken Juul · May 15, 2009, 05:36:38 AM

It is probably safer to check the glow plugs resistance than trying to manually attach to a battery. Can't tell you what it is, should be high, but not infinite or zero. I don't think 14v should hurt them either, they seem to be pretty bulletproof. Double check all you wiring, including the ground cables to ensure you are not focusing on a symptom rather than the cause.

Sorry not much help, this is a strange one.

prh77 · May 15, 2009, 06:00:50 AM

I think the resistance should be between 3-7 ohms, not much, which is why they draw so much current. I assume you are aware that these are Kubota parts, and are a fraction of the cost compared to Universal.

Craig Illman · May 15, 2009, 06:08:52 AM

Bob - I think it's probably the high voltage from the shore power charger. That's what I attributed it to on my boat. You shold be able to find replacements for less than $10 each at a Kubota dealer or online. I wish I had the NGK part number handy for you.

Craig

Stu Jackson · May 15, 2009, 07:04:31 AM

I typed in NGK glow plugs in the search box and found this: http://c34.org/bbs/index.php/topic,3347.msg20998.html#msg20998

I, too, originally suspected "high" voltage, but it would do you well to read the box and labels on the glow plugs which should indicate a range of voltages. I don't think it's that, but whadda I know...

There have been reports of people starting their engines while their shorepower charger is still on. It really doesn't do any harm, although I guess the chances of leaving the dock with the plug still in could be higher... The downside is that you don't know, until "you get out there Kitty," is if your reserve or house banks work and can start your engine.

Lance Jones · May 15, 2009, 07:24:38 AM

I can comment from recent experience that if your batteries are low/dead, the motor will not start even if connected to shore power

. It may just be the brand of charger that I have. I hadn't heard about an issue of starting the motor with shore power still attached. What is the problem with doing so?

Bobg · May 15, 2009, 07:42:29 AM

The part number for NGK is Y103V I called carquest and have 3 coming at $8.31 apiece, I called the tech people at NGK and a very knowledgeable fellow reminded me the plugs are rated at 10.5 volts, which is stamped on the plug. He said in all likely hood, the 14 volts burned out the plugs, he said even 12 volts from the battery is bad on the plug, and encouraged me to install a resister in the line limiting the voltage to 10.5 volts, now I have had my boat for 3 years and never had this problem with burning out previous NGK plugs, I wonder if the solenoid upgrade gives me too much honest voltage, (maybe the long #10 wire knocked some of the voltage down)
I do admit with the upgrade, for the first time, I held the plugs on for a long time, 40 seconds, the plug never felt even remotely warm, the tester was on showing 14 volts all the time. thanks for your input, it is highly appreciated. Bob

Bobg · May 15, 2009, 08:18:33 AM

Another idea, when I bench test the new glow plugs and ascertain they are working, I will then connect them to the wiring at the engine and before installing them in there perspective holes, I will again check them on the boat by grounding the plug, activate the power, to visually see if they are glowing, then I will know for sure weather it is something else or not.

Kind of wierd, "how hard can it be?" I mean unless I am missing something, the wire goes from the starter solenoid, to the switch, then back down to the plug, or in this case, the small nut on the solenoid, then to the plug. I don't think that there is a resister hidden in the system that went out, and why would (factory) install plugs rated at 10.5 volts with a 12 volt system. without a resistor of some sort. I do believe the old plugs were factory as they were painted same brown color as engine. I don't know guys, just all seems strange. Thanks again Bob

Stu Jackson · May 15, 2009, 09:26:30 AM

Quote from: pogmusic on May 15, 2009, 07:24:38 AM
I hadn't heard about an issue of starting the motor with shore power still attached. What is the problem with doing so?

The issue is that you have two sources of charging happening at the same time once the engine starts: the shorepower charger and the alternator. Many people over the years have done this, unknowingly, without harm. For those with solar panels, the panels charge when the engine is running, too, so two charging sources, in and of themselves, is not necessarily harmful.

It just doesn't make any sense, personally, to me, to have your shorepower charger on when you start your engine. If you're starting your engine, it means you're ready to leave the dock, so why start the engine before you disconnect from shorepower? Some like to "idle" their engines to "warm 'em up" before they leave the dock. This is one of the worst things you can do to a diesel engine.

KISS: turn your charger off, turn off the power at the dock, disconnect your cord, and then start your engine.

Stu Jackson · May 15, 2009, 09:29:56 AM

Quote from: Bobg on May 15, 2009, 07:42:29 AM
The part number for NGK is Y103V ...the plugs are rated at 10.5 volts, which is stamped on the plug. He said in all likely hood, the 14 volts burned out the plugs, he said even 12 volts from the battery is bad on the plug, and encouraged me to install a resister in the line limiting the voltage to 10.5 volts...

Bob, I must admit that after 11 years here, this is the very first I've ever heard of this, and some of us have had their boats for twice as long as I have and I look forward to their input.

Have you checked with a Kubota tractor engine dealer or with Universal (www.marinedieseldirect.com, Torresen, etc.) about this alleged "voltage to glow plugs" issue?

Stu Jackson · May 15, 2009, 01:39:43 PM

Expanding on the www.marinedieseldirect.com, here are a few other links there:

This is the general parts list: http://shop.torresen.com/marine_diesel_direct/Universal/index.php?p=include&contentsection=universal&contentname=engine&engine=M25

This goes to the glow plugs: http://shop.torresen.com/marine_diesel_direct/Universal/index.php?p=details&mfc=Universal&sku=299685

These are for M25 engines, find your engine and search away.

Bobg · May 15, 2009, 06:45:15 PM

Stu, I havn't talked to kubota or universal yet, but good idea, I bought the first set of plugs from a kubota dealer, using the universal part number, I got NGK Y1030v, same as the ones in my engine. I did notice the web site you provided and the plugs were 71 dollars apiece. too much for my blood. will go to the boat next wednesday and see what happens. I did the Ohm test and they are certainly shot. thank you and will provide a update next week. also I will install a 1/4 inch test lite you suggested. Bob

Ron Hill · May 15, 2009, 07:22:26 PM

Bob : Guess I'm confused and like Stu I haven't heard of this problem like this in the past 20+ years.
If your shore power is OFF (which it should be!!) I'm not too sure how you're getting 14V to the glow plugs. I usually see a 2 to 3 Voltage drop when I engage the glow plugs from a full battery bank of NMT 13 volts??

Stu Jackson · May 15, 2009, 08:22:58 PM

Ron,

Interesting unintended consequence of having your shorepower charger plugged in when you start your engine.

You could burn the glow plugs out!

I just KNEW there was another reason not to do that...

sail4dale · May 15, 2009, 11:41:55 PM

Wow! Learn something every day. I had my Cat 30 for 18 years and my Cat 34 for 7 years and would start my engine with the shore power on many times. When I just want to run it in the slip, the shore power is on. Haven't had a problem yet .... never saw any warning about over voltage on glow plugs. Is it in a manual that I overlooked? Or am I just lucky?