Glow plug failure diagnostics...

[Mouse]

Had another failure - getting valve and valve seat sorted locally but the glowplug also failed and I'm after some advice.

This is the condition of the glowplug in the side that just overheated and failed (again).
During the last hour of operation I can say there was a leaky valve - low compression and it was maybe sucking in a bit of sump oil through an oil leak in the rocker cover that was dripping onto the air filter.

Does it show classic signs of something being set up wrong.









A replacement is slim as its a 0.9Volt 40Amp beastie thats not fitted to anything I can find ad there was only one cross reference part I found but it was 10 mm to long. I can see me finding a modern slim glow plug the right length and hollowing out and threading the body of this one to take it

[sbrumby]

Is the engine direct or indirect? Some tractors have something like a glow plug which is also connected to the fuel supply situated in the manifold. When switched on a small amount of fuel is lit on the way into the engine. Maybe worth considering. By the way I once owned and ran a multicar skip waggon, size of a mini but could lift 2 ton and it had a diff lock as standard.

[Mouse]

urm there is a little chamber thing the injector squirts into then there is a 5mm(ish) hole into the main cylinder, this also houses the glow plug.
I cant photograph it as its at the engine place being fixed up.

[coachgeo]

urm there is a little chamber thing the injector squirts into..

What engine is this. Sounds like a pre chamber engine (swirl chamber) IDI type (Indirect Injection)

[Sphere]

urm there is a little chamber thing the injector squirts into..

What engine is this. Sounds like a pre chamber engine (swirl chamber) IDI type (Indirect Injection)

Motorenwerk Cunewalde 2VD 8/8 - 2SVL engine

[Crazymanneil]

Got a pic of a good glowplug?

Footery wee things aren't they? I busted 2 on my engine trying to remove them but they are still in there...

N

[Sphere]

I busted 2 on my engine trying to remove them but they are still in there...

I'm sure that brought you closer to God

[albertaphil]

How is your injection timing, mouse? That plug got very hot, and unless your engine is seriously overfuelled (which you would see by a cloud of black smoke) the only way to get that kind of heat in an indirect injection engine is from timing that is too far advanced.

In direct injection engines, bad injectors can cause similar heat damage to pistons. Not sure on IDI, though. How does your piston crown look?

[TedV]

Glow plugs are usually in the cup chambers of an IDI. Leaky injector or bad spray patern could do that damage

[Mouse]

Would sump oil dripping into the inlet manifold also cause similar problems?

[IgorVigor]

Oil dripping into the inlet manifold?

I wouldnt have thought so personally.
The olny time I have seem anything resembling that on a glow plug was from starting whilst the glow plugs were still being heated.

[Mouse]

Ah! so your suggestion is that I shouldn't have keep the glow plugs energised whilst cranking?

[TedV]

if the fuel squirts in and it's not hot enough to ignite, the fuel will coat the inside of the chamber. When it finally does ignite, the liquid fuel burns very hot and slower than the attomized fuel squirting out the injector. thats why leaky injectors can melt pistons, head, whatever. I've seen a head that looked like a cutting torch cut it. The injector was shooting a stream into the far side of the precup chamber melting the aluminum in its path. I'm not sure if the oil leak would do the same thing. Usually if an engine is bad enough to be that oil leaky, the fuel system and injectors have been ignored and are in bad shape too.

Oil leaking, if bad enough, can cause a run away engine. You turn off the fuel but enough oil is being sucked in to keep it running. With no proper timing when it is injected and ignites, it can be hard on the engine, bearings, etc.

Is there any way you can have your injectors pop tested to verify what presure they open is in spec and their spray patern is good?

[IgorVigor]

No, you shouldnt keep glow plugs energised when cranking...

They get too hot (I know that sounds silly seeing that they glow white hot when energised, but its true)

I dare say someone will come along and disagree with what I have said, but I have seen glowplugs out of a variety of different engines, and the only time I have seen deposits/damage to the plugs is when they were heated, and the engine cranked at the same time...

[Mouse]

The more I learn the more ignorant I realise I am!

Note to self: Keeping the glow plugs on dont make the engine start any better!

[Nanko]

Some plugs need only few seconds some more than 30 to get hot enough
Heating a 7 sec type for 30 seconds will melt the tip
So try to find out how much time the plug needs.
Cars use nice glowtime relays ,
If you decide to use such relay , I figured out how to connect them.

[andrewaust]

Agree! From what I see the plug/plugs have melted by keeping them on to long. Best bet is to place one in a vice "not to tight" and energise the plug, see how long it takes to go a nice cherry red colour, do not let it progress to bright orange as next will be white hot and death of the glow plug

Most glow plugs only have a 10-15 second duty cycle = meaning holding them on longer will burn them out. I will say glow plugs have different duty cycles depending on voltage. Some plugs have a lower voltage rating then the vehicles system as the resistance drops the voltage on the glow plug wire connectors "supply rail". The plug will have the voltage stamped on the side of the plug mostly where the Hexagon flat is. My old Nissan MQ Patrol has 23V plugs, as it is a 24V system. Some Toyota land cruisers use 11V plugs etc.

There's a lot of technology behind those simple plugs.

Another little trick using a glow plug engine! If a cylinder is missing you can measure the resistance of each glow plug whilst the engine is running, the one with the most resistance should be your bad cylinder. Word of warning measure all of the plugs resistance beforehand !!



A

[IgorVigor]

The more I learn the more ignorant I realise I am!

Note to self: Keeping the glow plugs on dont make the engine start any better!

To be fair to you, the engine will normally start easier with the plugs energised...
The plugs are at their hottest then, so when the fuel is injected, its most likely to start.
The problem is, the plugs, as I said before (and other agree ) arent designed to be energised when the engine is cranked...

Apart from the plugs being destroyed , do you need a little extra starting help?

If so, you could squirt a drop of oil (I mean a few millilitres) into the intake (after the airfilter )
Some stationary diesels had that feature (Lister LT1, like I have outside for example)

Oil doesnt take so much heat to ignite under compression, so it will burn before the diesel can.

Or you could try Easy Start (ether), but personally I hate the stuff...
Sure it works, but believe me, you engine WILL become addicted to it....

[sbrumby]

Engines getting addicted to easy start,is an old wives tale, you hear the expression a lot but its not based in fact. Farmers quote it a lot (and i am one). But what they fail to say is their tractor that was built before gunpowder, is lacking in compression,has a lazy starter,duff battery,injectors that have never been apart since they were born. Some engines were rubbish when they came out of the factory anyway. TE20 gold engine, Ford transit york engine, etc.
I swear by the stuff, if you are trying to start a lawnmower (petrol) that has not been run since OCT last year and refuses to start because the spark is weak but as its a pull start you cant get it to turn fast enough to get a good spark then useually a wiff of easy start does the job and will blow the cobwebs out of the engine.

[Sphere]

...build before gunpowder...

Hilarious Now my dog is eyeballing me, why I'm laughing out loud reading a diesel forum.

[thundercougarfalconbird]

HMMMMMMMM, easy start , hot glow plug and open intake valve = FIRE not always inside your engine, and your would not be the first with an extrnal combustion engine.
* keep the extingusher handy *

if you want a very durable glow plug that is self limiting, just use a delco 60G

[IgorVigor]

I think I may have worded my last post wrong :S

Right, here goes.

Engines CAN become addicted to easy start.

I know, because I know enough people who have had it happen.
I know of several people who have decided because in the winter their car takes 3-5 seconds to start (compared to 1-2 in the summer) even though they have got brilliant compression (and near enough equal across cylinders), new spark/glow plugs, etc.
They started using easy start.

The problem is now their cars wont start unless to crank them for 10-15 seconds, but if you give a blast of easystart instead, they start on the first spin...

And as for the external combustion engine :p
I have seen that too many times...
As you said, hot glow plug, open inlet valve, and whoosshh!

Then again, I have heard similar problems with all these fuel additives...
Never actually seen a problem, as I havent used any of them, but I have heard from people that their car/etc wont run smoothly without a shot of the additive.

Now whether that is just BS, whether it does make a difference (because they are so used to engine running on it), or whether they are just a big rip off....

[Mouse]

An old bloke told me the other day that the problem with easy start was that it causes such a harsh knock when starting a diesel ( and believe me its harsh if you've ever used it) that it knocks the carbon deposits from inside the chamber and that these deposits usually aid the initial combustion when the engine is cold. I dont know if this has any bearing on reality but I have tried to avoid the stuff because of the sounds that come from the engine when it does eventually start hence making the mistake of keeping the plugs energised. The old bloke then went on to recommend fly spray as a suitable alternative

As for petrol engines becoming addicted to easy start is usually down to a lazy owner not sorting out the underlining ignition / carburettor problem.

[sbrumby]

There used to be a load of people thought the earth was flat. You dont hear much from them these days. Unless you take an engine to bits to find out what is wrong everthing else is just hearsay. A new engine comeing out of a factory has no carbon but it starts. So if it doesnt start after some time has past there must be a difference between a new engine and an old engine. I have a peugeot boxer was a bad starter, smoked a lot, not much power, had cam belt changed, no different, had injectors reconed, no different, moved the pump timing just a bit, brilliant starter, no smoke,loads more power.

[IgorVigor]

Personally, if I for some reason an engine wont start, I would use a squirt of WD40, or similar...

Its usually enough for it to cough into life.

But I do agree, a lot is usually a lazy owner...
If they have no idea what to do to cure the problem, they wont spend out a bit of money to get the engine tuned a little better, but are willing to keep spending out on cans of easystart and fuel additives :S...

Most diesels that I have either worked on, or helped with that are a bit stubborn to start, a drop of oil into the intake works better than easystart...
And you dont get that horrible sound like you get with easystart :S

[Mouse]

I've been inspecting the head recently now that I've had it apart properly.
There is indeed a small valve thing that drops a drop of oil into the inlet manifold when you operate the decompresser lever.

I should have it back together in a few days.

[IgorVigor]

Should be nice when its back together

My project isnt off the starting blocks

Will you post a new video once its back together?

[albertaphil]

From anything I've read, using "easystart" (I assume you're talking about ether) in an engine with glow plugs is a recipe for engine damage. If you shoot starting fluid on a hot glow plug it will ignite when it shouldn't and you will likely be buying some engine parts. I think most starting fluid made nowadays has some sort of lubricant in it, but if the old farmers talked about engines getting addicted to easystart, it would be because ether will wash the oil off the cylinder wall, thus leading to premature wear of the piston rings=low compression=easystart must be used to start the engine. If you must use the stuff, make sure your engine is cranking when you spray it into the intake so as to encourage the fire to go the correct way out of the engine and so that you will get some oil to your cylinders more quickly.

I've also heard that ether can break piston rings, but it seems to me that if ether breaks your piston rings, then they were on the verge of breaking already.

Bad injectors wreck things. Here is a picture of what a bad injector did to the piston of my Cummins NHC 250. I have no idea how long it took for this to happen as I just bought the old truck, but there is damage to the adjacent piston from piston ring material that had blown back into the intake manifold and gotten sucked into the other cylinder. Fun fun:-)

Phil

[thundercougarfalconbird]

kewl pix phil, i should take some of my lister pistons from engine being overloaded and too much fuel. and yes ring breakage is also a side effect, i have a honda 50 and the previous owner used alot of easy start on it,the valves needed to be set, the top ring was broken, no other reason for it, it was not worn thin , no other problems other then broken.

[Sphere]

Rather nice "insight"