Help!! Loud Engine knock after changing glowplugs

[banjodunn]

G'day the more i read this the more i hope i am wrong for your sake But i still think you have done a crank bearing ( big end ), don't be fooled by the sound coming from the top of the engine as this can be the piston just travelling up the bore a little more and tapping the head( I know this from experience:ashamed. By all means check your valve train but i would be draining the oil and cutting open the filter to check for metal particles, I have seen an engine do a brg and not drop considerable oil press due to the gallery being half plugged by the failed brg. Hope it works out well for you


Jon

 

[TO_Bud]

Lots of ideas here for you to digest. You've titled your post as a loud engine knock but further down you post the noise can be heard above the engine from some feet away. A rod or bearing knock will be heard some hundreds of feet away, in fact the knock might be the only thing heard from a distance. Since the tempo of the sound stays constant on accel and decel it doesn't seem to be a rod or bearing so I'm with the posters on carbon build-up. Carbon build-up on a piston or cylinder can glow red hot while the engine is running. Any fuel leakage by an injector will be ignited before the piston is at it's proper location in the stroke causing rattling or dieseling (knocking sound if you will). It also doesn't sound like a destructive condition. I would try some fuel additive for moisture and some fresh winter grade fuel first before diving into the engine.
More advice hope it helps.

 

[BeeferMan]

Now I'm no expert here, but I'm having a hard time understanding the "carbon-knock" scenario in a diesel engine. Spark plug engine, ok, that'll happen when the glowing carbon (pre) ignites the fuel before the spark normally would. But in a diesel, there is no fuel to "pre-ignite" until the injector fires - and that's when it's supposed to ignite. So how could carbon in a diesel cause a early ignition condition and the subsequent knock?

Again, I'm not saying it couldn't, but please educate me as to how it could...

 

[Jerry/MT]

Now I'm no expert here, but I'm having a hard time understanding the "carbon-knock" scenario in a diesel engine. Spark plug engine, ok, that'll happen when the glowing carbon (pre) ignites the fuel before the spark normally would. But in a diesel, there is no fuel to "pre-ignite" until the injector fires - and that's when it's supposed to ignite. So how could carbon in a diesel cause a early ignition condition and the subsequent knock?

Again, I'm not saying it couldn't, but please educate me as to how it could...

The person who posted above you said "Any fuel leakage past an injector....". That's the postulated fuel source.

 

[BeeferMan]

The person who posted above you said "Any fuel leakage past an injector....". That's the postulated fuel source.

:thumbsup:

 

[OldBulldogger]

Update on the loud engine knock/tap. First of all, thank you to everyone who replied to my post. All of the input you gave was greatly appreciated and everyone seemed to have some very valid reasons for what could be causing the loud knocking/tapping sound. That is the best thing about these forums, we all get great information and can learn from other's experience.

I have to admit, I was pretty concerned after reading what could potentially be causing all the noise and the $$$ that could be involved to fix it. I purchased a mechanics stethoscope yesterday and I will say that was well worth the $20 after using it. Long story short, when I got home last night, I went out to the shed to take another look at the tractor after reading all the great information provided.

Admittedly, I am a praying man and believe in the power of prayer so I threw up a quick one to the good Lord and then started the tractor. The loud noise was still present. So I used the stethoscope to try to isolate the sound. It did seem like one cylinder in particular was a little louder and closer to the top end. I then jumped on the tractor and revved it up and down and listened. It continued to rap loudly keeping in sync with the RPMs. The tone changed with the speed - more of a loud tapping on the faster RPMS and more knocky on the slow rpms. I revved it up and down slowly three times and then ON THE THIRD TIME REVVING IT UP - the sound disappeared completely.

The engine idled like normal - no sound. I revved it up and down several more times - no sound. I then through it in gear and drove it around the yard, using the throttle and foot throttle to work through the RPM ranges - still no sound. I live about a mile from town so by then, it was good and warmed up so I drove it into town, topped of the tank with half a tank of new diesel and drove it home - again no strange sound. Parked it for the night and fired it up again this morning in 25 degree temps. The new glowplugs did their job and it fired right up (no more ether!). And again, no more loud knocking rapping sound.

Here is my take on this so far.

First, if you are a praying man, it never hurts to ask the good Lord for a favor! I can honestly say I have been blessed many times in my life by the man upstairs, especially when on bended knee. Enough said.

Secondly, I think the post from ZZVYB6 (read above) fits. In this case, the glowplugs I changed were original and 22 years old and all had carbon build up, the center one worse than the others. And, coincidently, the loud knocking occurred AFTER changing the plugs. Sure, something else like a main bearing or rod bearing could have failed by coincidence at the same time however it would seem unlikely. (never say never though!) The one variable in the whole before and after review was pulling the plugs. It would make sense that if there is considerable carbon build up that some carbon was dislodged and floating around in the head until the point where it blew out in the exhaust after revving up the engine several times. I will admit I am surprised by how loud of a sound it made. I did talk to my local Ford/NewHolland dealer and they did say it is possible and could almost sound like someone threw a small rock into the combustion chamber. Good news is that it is gone and the tractor is running smooth as before.

I will keep this post alive with a few more updates so as not to rule out anything else and let everyone know how long term this played out. In the meantime, I love my Ford 1720 again. Okay, I never really quit loving it... I must be a tractor junkie. I have to say, they are great little tractors for their size.

If anyone has additional feedback, I would like to hear it. I learned quite a bit so thanks again. The feedback was great.

 

[Transit]

It sounds as if something loosened up, I'm thinking a valve hung up or piston slap.

 

[banjodunn]

G'day glad to hear it is ok :thumbsup: I dont mind it when i am wrong on these things

Jon

 

[Raspy]

Sounds like you got the problem resolved. Good.

If it continues, I think you should explore all options with the injection system first.

So, first off, a bad injector on a mechanical injection engine does not affect timing. Second, idling diesels do not fire prematurely from hot carbon. They can't, there is no fuel there to fire until injection occurs. However, an injector can fail by making a poor spray pattern. This means more of a jet of fuel than a fine mist. When this happens the fuel ignites with more of a bang and a knocking sound. It also makes a lot of carbon.

I suggest you crack the injector line on the carboned up cylinder, while the engine is idling and knocking. If this stops the knock and makes it run rough, you know it's an injection problem.

If it is an injection problem on that one cylinder you'll need a set of injectors, or yours rebuilt by a qualified diesel shop. And when you get that taken care of go out and work it at full throttle for a while to clean out the deposits so the corrected spray pattern is not spraying on a carbon buildup. It needs to spray cleanly into the combustion chamber and ignite while atomized.

A fuel knock can be unnerving and sound much more serious than it often is. A rod knock is more of a pounding down low in the block, and likely develops over time to become gradually louder. But all bets are off with the use of ether! I've seen broken pistons, rings, and crankshafts that resulted from ether. One man's "small" squirt is another man's flood. If you absolutely must use ether, and I mean absolutely! Just give the engine enough to smell it. That's all! No liquid! Just the scent of ether does the trick. More and you are likely causing damaged ring lands and future compression loss, or worse.

But I have to draw the line at praying for a fix. Doesn't the Lord you pray to have better things to do than take care of your tractor? And, If I was him, I'd point out that you have been deliberately hurting your engine with ether and likely caused some damage yourself.

 

[dqdave1]

I had an injector that was bad and it ran pretty smooth. It was just down on power. You may not know you are down on power since you got it with a bad injector. Ask dealer what fee is to check injector. Another way to get piece of mind for about $25.00 is to do an oil analysis. I use Blackstone Labs. They will send you the needed items for free. Warm up engine; drain oil; catch a little in supplied bottle and send it to them. They will check oil and send a report to you. If you have bearing problem , it will show up. If you have alot of "soot" in oil; it will show up and on and on.
I use my stethoscope all the time. Pinpoints noises quickly.
Glad you may have a cheap fix.

 

[wvpolekat]

Sounds like you got the problem resolved. Good.

If it continues, I think you should explore all options with the injection system first.

So, first off, a bad injector on a mechanical injection engine does not affect timing. Second, idling diesels do not fire prematurely from hot carbon. They can't, there is no fuel there to fire until injection occurs. However, an injector can fail by making a poor spray pattern. This means more of a jet of fuel than a fine mist. When this happens the fuel ignites with more of a bang and a knocking sound. It also makes a lot of carbon.

I suggest you crack the injector line on the carboned up cylinder, while the engine is idling and knocking. If this stops the knock and makes it run rough, you know it's an injection problem.

If it is an injection problem on that one cylinder you'll need a set of injectors, or yours rebuilt by a qualified diesel shop. And when you get that taken care of go out and work it at full throttle for a while to clean out the deposits so the corrected spray pattern is not spraying on a carbon buildup. It needs to spray cleanly into the combustion chamber and ignite while atomized.

A fuel knock can be unnerving and sound much more serious than it often is. A rod knock is more of a pounding down low in the block, and likely develops over time to become gradually louder. But all bets are off with the use of ether! I've seen broken pistons, rings, and crankshafts that resulted from ether. One man's "small" squirt is another man's flood. If you absolutely must use ether, and I mean absolutely! Just give the engine enough to smell it. That's all! No liquid! Just the scent of ether does the trick. More and you are likely causing damaged ring lands and future compression loss, or worse.

But I have to draw the line at praying for a fix. Doesn't the Lord you pray to have better things to do than take care of your tractor? And, If I was him, I'd point out that you have been deliberately hurting your engine with ether and likely caused some damage yourself.

Cracking a line and quieting a noise does not always mean it is an injector problem. That also unloads the bearings. It can help narrow it down to a particular cylinder and is a good troubleshooting step.

I do agree on ether. Bad juju.

 

[Jerry/MT]

Sounds like you got the problem resolved. Good.

Second, idling diesels do not fire prematurely from hot carbon.

They can IF the injector is leaking.

 

[Raspy]

They can IF the injector is leaking.

Mechanical injection systems only send pressure to the injectors when it's time to inject. They have no or almost no pressure until then. When the injection pump sends pressure, it's time to fire and not early. All fuel is burned and there is nothing to fire until the next injection event.

Idling diesels have a hard time warming up because they have so much excess air being pumped through them. This means a cool combustion chamber and no glowing carbon sitting around to fire fuel that hasn't even arrived yet.

If these engines can sit without running and have an electric transfer pump running and bad injectors, they can slowly leak and hydraulic a cylinder, but otherwise run just fine even with a severely reduced pop point or a plain old leak. There is just not enough pressure to cause enough fuel to leak past a bad injector, between injection events, to be ignited early enough, in an idling engine, to be a loud knock. This theoretical situation just doesn't exist in the engine in question, that started up cold and knocked. His problem was about loose carbon, or a broken glow plug tip or poor atomization. Not hot glowing carbon in 25 degree startup.

High pressure common rail injection systems have very high pressure at the injectors all the time and can fail differently.

 

[Jbrink64]

Perhaps the man upstairs was making the noise to wake you up. Glad the noise went away.

On a mechanical fuel system, a leaky injector will affect timing. At the end of injection, the nozzle will close and hold pressure (just below cracking pressure) for almost 15 seconds.

Back at the injection pump, each pumping unit has a delivery check valve mounted just above the plunger. The idea is to maintain a near cracking pressure in the injector-fuel line-upper pump chamber until the next injection phase.

When an injector leaks, three scenarios happen.
1) a small amount of fuel dribbles into the pre-combustion chamber. This fuel smolders, and burns unevenly. Also causes soot.
2) the pump plunger needs to travel farther to bring the injector-fuel line-upper pump chamber up to the cracking pressure, causing the point of injection to be late.
3) a small amount of combustion gases (exhaust) during the power stroke, or air during the compression stroke, can be pushed back into the injector. This acts like having air in the fuel system, and further complicates timing.

I would definitely have the injectors tested for opening pressure, and leakage.

 

[OldBulldogger]

Thanks again everyone for the input. Seeing how I just got this tractor, I am in the process of changing out all the fluids and filters to establish a baseline for myself. One question I have is regarding the product SeaFoam. I have read where adding this to the oil is beneficial for many reasons. I would like to get your perspective on this. Also, my manual says to add 4.8 quarts of oil with a filter change. My question is this, to you add the Sea Foam in addition to the 4.8 quarts already in or do you cut back the oil appropriate to the amount of Seafoam ounces added so as not to over-fill?

I will look into the injectors as well being the one cyclinder had quite a bit more soot than the others.

 

[MD09]

One thing I completely overlooked... The#2 cylinder is sooted up, you changed the glow plugs I assume because it was hard to start. The soot in the #2 cylinder is most likely from a malfunctioning Glow Plug.

 

[Caliche]

Originally Posted by Raspy

"But I have to draw the line at praying for a fix. Doesn't the Lord you pray to have better things to do than take care of your tractor? And, If I was him, I'd point out that you have been deliberately hurting your engine with ether and likely caused some damage yourself. "


If your favorite son's tractor was broken and asked you for help, would you tell him you were busy with more important issues?

 

[Raspy]

Caliche,
I don't want to pop your bubble, but I'm not the Lord and have never claimed to be. I spend a lot of my time helping my family, my friends, my neighbors, my relatives and my customers. Always have and always will. I also take responsibility for myself and don't pray for favors from the Lord for tractor issues or any other little inconvenience that life brings. Or, maybe it would be better said that, the Lord helps those that help themselves, or why sit around praying when you can do a simple analysis of the problem and solve it yourself using the God given common sense that most of us have for that specific reason.

It's a matter of taking responsibility for ones self.

Someone that gets up and approaches a problem they are having, with their tractor for instance, with a wrench and some thought, will always do better than someone who simply sits and prays for the problem to go away or be fixed by divine intervention. Are you confused about that?

 

[Jerry/MT]

Mechanical injection systems only send pressure to the injectors when it's time to inject. They have no or almost no pressure until then. When the injection pump sends pressure, it's time to fire and not early. All fuel is burned and there is nothing to fire until the next injection event.

Idling diesels have a hard time warming up because they have so much excess air being pumped through them. This means a cool combustion chamber and no glowing carbon sitting around to fire fuel that hasn't even arrived yet.

If these engines can sit without running and have an electric transfer pump running and bad injectors, they can slowly leak and hydraulic a cylinder, but otherwise run just fine even with a severely reduced pop point or a plain old leak. There is just not enough pressure to cause enough fuel to leak past a bad injector, between injection events, to be ignited early enough, in an idling engine, to be a loud knock. This theoretical situation just doesn't exist in the engine in question, that started up cold and knocked. His problem was about loose carbon, or a broken glow plug tip or poor atomization. Not hot glowing carbon in 25 degree startup.

High pressure common rail injection systems have very high pressure at the injectors all the time and can fail differently.

Idling diesels do have a hard time warming up for the reasons you stated, However cold is a relative term. The peak gas temperatures in the cylinder just due to compression (CR=17) are on the order of 900F. It's even hotter when you add idle fuel. Not nearly as hot as when running at power but certainly> 900F is a tad warmish.

As far as the pressure across the injector, I think you'll find that the injectors are pressurized and they can and do leak fuel if they are worn or dirty and do not seal properly. If it was direct injection diesel, you can burn a hole in the piston from an injector leak.

 

[Raspy]

Burning a hole in a piston from an injector leak, or missing tip, is because of a jet off fuel rather than the designed spray pattern. it's a common problem, but not the problem being discussed in this thread. The correct spray pattern is very important for proper combustion.

Your theory that 900 degrees is enough to warm an engine misses the point. Its not the instantaneous temperature the combustion chamber reaches, it's the BTUs delivered to the block. Diesels have, whether you like it or not, a lot of excess air pumping through them all the time at light loads or while idling. This makes them hard to warm up in cold weather while idling. And they are not likely to have glowing carbon standing by at cold startup to prematurely fire the fuel that isn't even there yet, unless there is some kind of serious malfunction.

Please, no need to argue a silly point. Old bulldogger simply asked why it would be knocking at cold startup, at 25 degrees. All BEFORE it had time to warm up.