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Glow plug test

HerbertFriedman

Member III
Had some difficulty starting my Universal M25XP and I suspect the glow plugs. It took a very long while to start, battery cranked the starter motor just fine and after the engine ran for a few minutes (and probably heated up), it would restart just fine. Maybe the glow plugs were not operational and the cold weather (maybe 50 degrees) made starting difficult. Can I just remove them one at a time and press the glow plug button and see if they light up? I would keep the power wire connected and ground the plug housing with a clamp.
 

footrope

Contributing Partner
Blogs Author
Too late I already pecked out this reply. That idea might work. Do you have a voltmeter in the circuit for the start battery? Or put a voltmeter across the battery while you activate the glow plugs. You're looking for a significant voltage drop with good plugs. Maybe as much as 0.5 to 1 volt. If you take one out and power it, let us know if it actually glows.

How long did you apply the glow plugs? Did you activate the glow plugs while you cranked? I struggled with occasional cold starting problems for several years. I began to use plenty of glow even when air temps were warm. Keeping the plugs glowing when cranking really helped reduce crank time and now I don't have any starting problems. I replaced the battery, too, but that alone didn't solve the hard starting on my 4 cyl. 5432.
 

HerbertFriedman

Member III
thanks for the suggestion about the voltage drop on the battery. Not sure if the glow plugs are fed off the starting battery or the house battery but I suspect it is the starting battery. I do have a voltmeter reading the voltage at the alternator (as well as a shunt for an ammeter reading) but I can easily put my voltmeter on the either battery, just need an extra pair of hands to push the glow plug switch. It could also be the relay but I am not sure how that is wired, I need to check.

My first plan is to push the glow plug switch for say 10sec and then feel each one of the glow plugs to see if they are hot. If all are cold, then it should be a wiring or relay problem, if only one or two are cold then it probably is the glow plugs themselves. I see no record in the previous owner's notes of any glow plug replacement and since this the original engine circa 1987, I may need new glow plugs.

A previous thread identified the glow plugs as NGK Y103K, available on Amazon for about $10 each or directly from Universal at about $80 each. Imagine that!!!
 

HerbertFriedman

Member III
I have some questions concerning the removal of the glow plugs. I just bought three NGK Y103K and plan to replace the old, probably original ones. Christian reported that although the middle one was hard to remove (only 1/8 turn with an open end wrench) it was possible to remove all three without removing the exhaust manifold. Other threads said you must remove the exhaust manifold. Can anyone clarify this point?

Also Christian reported that he moved a water hose, removed the air filter and removed the return fuel hose for better access. Do you have to bleed the engine if you remove the return fuel hose?

From the photo of the glow plug, the 12mm wrench goes on the body of the glow plug. I dont understand Christian's comment about the knurled nut. Is this nut just to secure the jumper wires? And if so, with no flats does one just hand tighten the nut and ust eh slot for a screw driver blade to tighten just a little more than hand tight?

Is there any sealant, like Permatex Aircraft grade, needed on the threads or just the crush surface below the flats to make seal, in much the same manner as a spark plug on a gasoline engine?

I plan on doing the touch test and the voltage test but I suspect that since the engine has always started easily, that the wiring is OK but glow plugs do burn out.
 

supersailor

Contributing Partner
The glow plug switch (the push button) at the instrument panel has twice failed in the four years since I bought this boat. Check the switch before doing the glow plug change.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Recall that my glow plugs turned out to be fine and new ones were unnecessary. They're as sophisticated as a toaster, not much to go wrong.

More likely it's the switch or the grounds or the wiring.
 

footrope

Contributing Partner
Blogs Author
I have some questions concerning the removal of the glow plugs. I just bought three NGK Y103K and plan to replace the old, probably original ones. Christian reported that although the middle one was hard to remove (only 1/8 turn with an open end wrench) it was possible to remove all three without removing the exhaust manifold. Other threads said you must remove the exhaust manifold. Can anyone clarify this point?

Also Christian reported that he moved a water hose, removed the air filter and removed the return fuel hose for better access. Do you have to bleed the engine if you remove the return fuel hose?

From the photo of the glow plug, the 12mm wrench goes on the body of the glow plug. I dont understand Christian's comment about the knurled nut. Is this nut just to secure the jumper wires? And if so, with no flats does one just hand tighten the nut and ust eh slot for a screw driver blade to tighten just a little more than hand tight?

Is there any sealant, like Permatex Aircraft grade, needed on the threads or just the crush surface below the flats to make seal, in much the same manner as a spark plug on a gasoline engine?

I plan on doing the touch test and the voltage test but I suspect that since the engine has always started easily, that the wiring is OK but glow plugs do burn out.

Maybe I can help a little. It is the intake manifold that may get in the way of getting a wrench on the glow plugs, isn't it? It's much less involved to remove than the exhaust manifold, but on the 5432 it's tough to get to all of the bolts.

You may have problems with the metal injector lines getting in the way of the glow plug removal and the intake manifold removal. If you remove one or more injector lines, then bleeding will be required. Removing a rubber return line from an injector doesn't require bleeding. The picture shows a couple injector lines removed and the knurled nut on top of the plug. There may be tiny lock washers under the nuts, too.

The knurled nuts. It may be hard to get to one or more of them with fingers. You have to be careful not to torque them excessively, whatever tool you use, so the answer is 'yes' it just secures the jumper wires and should only be hand tight.

I wouldn't use any sealant. The plugs are meant to seal metal to metal and that provides a ground, just like a spark plug. I put a tiny bit of copper-based anti-seize on the threads of each plug. Make sure the hole in the cylinder head is as clean as possible where the plugs seat.

I think you have a good plan. Definitely check wiring and relays before tackling the removal of the plugs. My plugs were old and ugly but worked great. If you can get the wires off each plug you can easily test continuity and resistance with an ohmmeter, too.

20160727_143754-small.jpg
 

HerbertFriedman

Member III
Craig, thanks for the clarification, I will look carefully to see what the physical situation is before I try to remove any plugs.

Bob and Christian, concerning the glow plug switch, first, I have not done the re-wire job to separate the glow plug switch from the starter switch. So I need to press both the glow plug switch AND the starter switch in order to start the engine. When I do press both, the engine cranks over but does not start, at least easily. If the glow plug switch were bad, the I would expect that the starter switch would not crank the engine, but probably I dont understand the wiring.

There is a small part next to the engine that looks like it could be a relay for the glow plugs, but again, in a normal relay, there are two low current wires to operate the relay coil, then two high current contacts to power the glow plugs. I do see the high current wires going to the glow plugs but I dont see any low current wires. But I will look tomorrow and take some photos.

I will try to remove the jumper wires and do a resistance check tomorrow, let you all know.

Again thanks, this is a great site with lots of mavens.
 

HerbertFriedman

Member III
just another thought, I guess the easiest test to do is to see if I get 12VDC at the glow plugs with the glow plug switch on and the input wire disconnected ? Or use my DC clamp on ammeter to see if there is current in those jumpers? That and the hot touch test.
 

HerbertFriedman

Member III
Recall that my glow plugs turned out to be fine and new ones were unnecessary. They're as sophisticated as a toaster, not much to go wrong.

More likely it's the switch or the grounds or the wiring.


Christian, just a question on your very nice 2014 thread showing glow plug replacement: You say that initially one glow plug was hot while the other two were cold. Then after replacement you found that all three old plugs were good and that the problem was probably wiring related. I am a bit confused, if one plug was hot then the wiring problem must have been with the jumper wires connecting all three plugs in parallel, and that the feed to the plugs was probably not the problem. I know you must have changed the entire wiring but was it the jumper wires that was the main problem?

And in case the plugs are my problem (and not the switch, wiring or relay, if there is one), am I correct that you were able to replace all three without removing the intake manifold. It may have been difficult and time consuming, but was it indeed possible?

Again thanks, Herb
 

footrope

Contributing Partner
Blogs Author
Good analysis on the glow plug switch. You should be able to put the meter on the end of any of the glow plugs you can get to, leaving the wiring intact. They're in parallel so the reading will be the same regardless of which one you connect your positive lead to. It also won't matter if you have a bad plug, you should see voltage regardless. You're looking for about 12 volts or so with the plugs activated.

If you need an extra "hand" to be able to see your meter you can extend the leads of your voltmeter so that you can place it in the companionway and watch it. I have also used my phone camera in the movie mode to record what happens when I can't see the indicator during tests. Worked great when I was doing compression tests.

I hope it's an easy troubleshooting process and a quick fix.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Herbert,

I think I concluded that the finger test for glow plug heat is just unreliable. One seemed hot , the others weren't. It was unreliable data.

I believe you have an Ericson 34? I had a 32-3, which has an M25 engine with very good access, especially compared to an E381.

On that model, the glow plugs were just an awkward reach, typical of engine stuff. You could get a 12mm spanner on the plugs, but the angle had to be right and patience was required. On that installation there was no need to remove anything big, just whatever hoses are in the way for convenience.

Might be quite different on your model.

An easy way to test the glow plugs, when you get them out, is to run a heavy wire from the battery pos terminal to the glow plug top, then hold the base against the engine block. No need for anybody else to push the cockpit buttons.

FWIW, I'm not a mechanic. My approach is just plunge in, figure things out, go off an buy the right tool, and expect a lot of first-time head scratching. If you do screw something up completely, then just call in a real mechanic to clean up the mess.

You do have to get dirty just to understand the issue. It helps to remember that if they put it on, it should be possible to take it off.
 

Kenneth K

1985 32-3, Puget Sound
Blogs Author
On my M-25...

On the knurled nuts: You'll probably need a screw-driver to loosen them if you haven't had them off before. The slots in the nuts look odd because they're so far off-center. Find a wide-blade screwdriver that fits the slots and you'll be surprised how they rotate just like normal screws. As for re-tightening, I think you have the right idea--finger tight then maybe another 1/8 to 1/4 turn with the screwdriver. I haven't changed glow plugs, but I did remove and polish all the contacts on the jumper wires.

As to removing the intake manifold: It seems I recall a previous post where an owner said the glow plugs "almost" went in/out without removing the manifold. The problem was the overall length of the plugs--the top threaded posts (that accept the knurled nuts) were hitting the manifold during removal/re-installation. The owner suggested that snipping or grinding off any unneeded extra threads on the posts might have helped the installation.

As to possible wiring problems: I have not yet re-wired my starting circuit either. I do know that when I hold the glow plug switch in, the panel lights and the oil pressure light both dim slightly and the clicking noise from the fuel pump changes noticeably. All these are signs of both 1) inadequate wiring, but also 2) that the glow plugs are in fact drawing a lot of amperage (I believe they draw 7 amps each). My engine (M-25 with 2100 hrs) was impossible to cold-start when I held the glow-plugs for the recommended 20 seconds. I decided to energize the plugs for a whole minute, then wait two minutes for the cylinder heads to absorb the heat, then hold the plugs for another full minute. It worked so well that I now do the routine as 45 sec--2 min--45 sec for cold-starting. Again, this works for my set-up which I know has inadequate wiring (the glow plugs are likely getting much less than the recommended power). As someone (MaineSail, perhaps) suggested in a re-wiring post, if you install a solenoid for the glow-plugs (along with the proper wiring), you'll need to energize them for much shorter times or you'll burn them out.

Best of luck.
 
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supersailor

Contributing Partner
Herb,

I was able to remove and replace the glow plugs with only removing the air filter on my M25XP. I would check the voltage at the glow plugs with them still hooked up and a helper pressing the button. This will give you the voltage drop. My reading was 9.7 volts. My glow plugs weren't acting as red hot diesel igniters. They were acting more like baby bottle warmers. After my rewiring, they read 11+ volts at the glow plugs. The engine now starts with 10 seconds of glow in the coldest weather (28 degrees and lower). On the original wiring, the path of juice was through the ammeter to the ignition switch then to the glow plug switch then through that god awful trailer harness to the glow plugs. My harness went forward to the front of the cockpit locker then doubled back to the back then went forward to the engine and glow plugs. All in all about 30' of undersized wire running through an ignition switch that was maxed out amperage wise. The plugs on the harness got quite hot during this little exercise. No surprise as a slide together plug does not have the positive contact that a screwed down terminal has. Main Sail has an excellent article on this subject and the current Good Old Boat online has just got one on how to cook a wiring harness.

These trailer plugs were never a great idea and I consider them to be outright dangerous in a 20+year old installation. It is smart to go over the wiring harness with an infrared temperature gauge. The temp readings at the plugs can be shocking. I used a heavy duty relay so the heavy duty current only goes three feet from the batteries to the glow plugs. The voltage drop is minimized and the fire starting high current isn't running all over the boat.


Oh and I also threw away that air filter and put a K&N on. It didn't seem bright to have all those metal shavings sitting right on top of the intake manifold.
 

Kenneth K

1985 32-3, Puget Sound
Blogs Author
Glow Plug Relay

Bob,

Do you have the details/specs handy for the relay you used? The choices are pretty overwhelming when searching for "12 volt relay" online.
 

HerbertFriedman

Member III
I too have a relay although no idea what one the Previous Owner used. But I did just measure the DC current and it was 30A. Sort of makes sense, it is reported that the resistance of a glow plus is of the order of one ohm so that for 12VDC, that would be about 10A for each plug or 30 A for all three. So you need a 12V relay with 30A capability.
 

HerbertFriedman

Member III
update: Went to my boat this afternoon to check out the glow plugs and here is what I found:

A previous owner did install a glow plug relay so that the glow plug switch on the instrument panel only activates the coil of the relay which is located on the port wall of the engine compartment, see attached photo. Also he rewired the glow plug and starter switches so that they are independent, wish he would have documented these changes. So now the #10 grey/blue stripe wires carries only low current, still goes through the dreaded trailer hitch connector but low current.

The relay is wired so that the green #10 wires goes directly to the starter post where you get 12VDC when you turn on the main battery switch, and this starter post is wired through the main battery switch and then to the starter batter, so lots of current available. Pressing the glow plug switch (with the ignition key on)) puts 12.5VDC across all three glow plugs so no short there, still could be open but no short.

With my DC clamp on ammeter (best instrument ever) I measure 30 A to all three glow plugs. The resistance of each glow plug is reported to be of the order of one ohm so I would expect 10ADC for each plug or 30A total. So it looks like all three plugs are OK.

The engine did start after a 10 sec glow plug heat but took 1-2 sec to catch, so there still may be a problem but I think it is not related to the glow plug switch, relay or the plugs themselves. Before took many tries to get the engine started and a good explanation would have been no glow plug action, so maybe the switch or the relay are intermittent. Certainly others on this site have reported intermittent glow plug switches. I have ordered a new glow plug switch, the present one is probably the original so makes sense to change it out.

Bob, I am amazed that you removed all three glow plugs without removing the intake manifold and maybe even some of the fuel lines, see the attached figure. You can see the glow plug jumper wires just below the black wires and even make out the nut on the front glow plug just behind the center fuel line. I can probably twist off the nut holding the jumper wires with a long nosed vice grip, getting a screw driver blade in there with the intake manifold in place looks impossible. But how did you get a 12 mm open end wrench on the glow plug itself and still be able to turn it. Maybe on the rear one but the front and middle plugs look like I could get a wrench on it but no room to turn. Did you make a special wrench, like a "crow's foot" or something?

Christian, you said you removed all the plugs on your M25, the photo is of my M25XP, is there really more room on your engine??

For anyone who has removed the intake manifold, were you able to get at all the bolts, and did you need PB Blaster of Kroil and if so where exactly did you squirt it? Squiring the bolt head does little and squirting the base of the intake manifold looks hopeless because of the gasket there?








































glow plug relay.jpgengine top.jpg
 

supersailor

Contributing Partner
Ken, I used a Bosch 30 amp heavy duty relay. I am currently in Portland so I don't have the Model number handy. I can get it after I return North.

Herb, That relay looks rather on the old side and the posts look like they have corrosion on them. Try removing the wires, cleaning them with contact cleaner and sanding the terminals with fine sandpaper and reassembling with a glop of di-electric grease on them. You may want to do a preventive replacement of the relay because this is a crucial system. I carry a spare on board just to keep Murphy at bay. Be sure the previous owner put a fuse in between the battery and the relay. This circuit is the closest thing to a dead short you have in your electrical system. Don't use a blade fuse or a glass fuse. Use a post fuse and have spares.

We went up the Columbia River Gorge today to do the Hood River Christmas Train for the two little ones. Holly Cow the wind was ripping! There was spume flying off the water and the car was jigging all over the road. It was calmer at Hood River, thank goodness. With an ambient temperature of 34, the wind chill was out of sight.
 

HerbertFriedman

Member III
Bob, the train ride on the Colombia River Gorge sounds great, we have been looking for nice vacation sites in the US, foreign travel has gotten to be such a hassle. Will probably tour the Colombia River Gorge region next summer.

Regarding the fuse issue on the relay for the glow plugs, the PO did not install any fuses and I agree this is a serious short coming which I will correct. But my current measurement has raised other issues. I did measure the DC current on the connecting the glow plugs with the output of the relay, the green wire in my picture. It was 30 amps so as I said, I believe all three glow plugs are OK, but the ampacity curves indicate that the maximum current for a #10 gauge wire is just 30A so there is no margin there, not a good electrical engineering design, but then again, not putting a fuse aint exactly good design either. Another case of good intentions and bad follow thru.

Now the original Ericson design also had a #10 wire feeding the glow plugs and that wire went all the way back to the instrument panel, through the glow plug switch and back to the glow plugs, and through those terrible trailer hitches. What a disaster waiting to happen. So I can understand why the PO just rerouted the wiring and installed the relay, but he may not have done a current measurement and just copied the Ericson design using #10 wire.

So my issue now are should I change the wire size from the starter post to the relay and from the relay to the glow plugs to say #8 wire? And what fuse rating to use? Safety on one hand versus 30 years of trouble free operation on the other?

In any case, I will install a Blue Seas terminal fuse block with some fuse. The fuse block is rated for fuses 30 to 300A so I would probably put in a 50A fuse just to make sure the present 30 A current does not blow the fuse.

As always your suggestions are appreciated.

Just one more question, regarding the replacement of the glow plugs without removing the intake manifold. Aside from removing the knurled nuts for the jumper wires, were you able to get glow plugs out with just an open end wrench, any tricks or special wrenches??
 
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