Help!! Loud Engine knock after changing glowplugs

[OldBulldogger]

I need some help.

I recently purchased a 1989 Ford 1720 with 3350 hours on it. I have used it for several weeks with no issues - all sounds normal. When it was cold (below 40 degrees), the previous owner would occasionally use a very small shot of ether in the air intake to get it started. I had to do this also and it would always start right up. He had replaced the relay to the glowplugs but still had trouble starting it when cold.

This weekend, I picked up 3 new glowplugs and replaced them. Before replacing I blew high pressure air around plugs to blow dust/debris away from falling in empty chamber. When I pulled the old ones out, I noticed that the center one seemed to have quite a bit of soot like black powder on it. The two outside ones seemed about the same and pretty clean compared to the center one. After replacing the glowplugs, I cycled the relay with the key until the indicator light went off showing the engine was ready and then started the engine. It was about 25 degrees out.

I had accidently had the throttle pushed forward to a near wide open position when it started. It instantly fired right up without needing any ether. I saw/heard that it was revved and I immediately (within seconds of starting) moved the throttle back to about 1000 rpms. I let it idle for while I went about cleaning up my tools to let it warm up. Everything sounded normal and it ran smooth. About 5 to 8 minutes after starting and idling, it all of a sudden starts making a loud knocking/clacking noise that it has never done. I did not notice any blue smoke but the knock continued. I shut it off checked the oil, everything is fine and to the level. I again started it and it knocks continuesly - no smoke. If I rev it up, the knock continues only faster. Hydraulics all work fine both the FEL and three point.

Let it sit overnight and started it again this morning while it was cold out- 25 degrees. It started great - again not needing ether so new glowplugs must be working fine now but again, it continues to have this loud knock coming from the engine. Engine does not run rough, seems to fire in rythm just a loud knock. I only let it run for a coulple minutes and then shut it down for fear of damaging anything further.

I am at a loss for why the sudden noise. Could I have knocked some carbon buildup inside the combustion chambers loose when I pulled the glowpugs? They appeared to be orignal - 22 years old with blue paint from factory. Even if I knocked some carbon buildup loose changing the glow plugs, could this cause this kind of knocking noise in the engine?

I really need some sound advice here before proceeding. I don't have a lot of tools to tear into the engine or check certain clearances etc. It will probably end up in the shop and I want to minimize my cost.

Please share your thoughts if you have any ideas! I would really appreciate it!!

 

[Skyco]

I'd pull the new glow plugs back out and have a look....it is possible one was defective and the tip came off.
If it did you probably will have to pull the head and have a look....

 

[frankhinde]

Something has happened.

The last thing you changed was the glowplugs so pull them and check to see they are all intact before starting that engine again.

If they are all there..Compare the length of the new glow plugs with the old ones just to make sure they are not protruding inside the chamber further and hitting the piston.

If they are, replace with the old GP's and restart to see if the noise is still there.

As the noise did not happen immediately upon replacing the GP's it is unlikely they are protruding to far..or if they are maybe a pitson broke the tips off.

Like the poster above said you will probably have to pull the head to get the remains out.

Now if the GP's are perfect and show no signs of impact damage then something else has hapened.

Knocking usually comes from big end bearings, but this is unrelated to the GP's.

Good luck and tell us what you find.

Frank

 

[OldBulldogger]

Ok, I pulled the new glowplugs and they are intact. I did not notice anything wrong with them. Center one definitely has more soot than other two. When first starting I do get initial puff of dark exhaust but clears right away. It has always done that. Listen closely to the noise and it is more of a loud tap than a knock. Any thoughts now?

 

[dqdave1]

Check injector on cylinder with soot. Use a mechanics stethoscope to isolate tapping noise. A piece of metal against your ear can work also.

 

[Caliche]

If you turn over the engine with the starter with the glowplugs removed, do you hear the sound in question? A short burst should tell you.

 

[Transit]

How are the gaps from the rocker arm to valve stem set? You could be hearing a slap if the gap is too wide.

 

[banjodunn]

G'day hate to be the one to say it but i think you have done a big end bearing I think it was pure coincidence that it happened just after you changed the G/P. Don't know how easy it is to drop the sump on your machine but that is where i would be heading


Jon

 

[MD09]

Ok, I pulled the new glowplugs and they are intact. I did not notice anything wrong with them. Center one definitely has more soot than other two. When first starting I do get initial puff of dark exhaust but clears right away. It has always done that. Listen closely to the noise and it is more of a loud tap than a knock. Any thoughts now?

Since your knock started sudenly if sound liek something let go. Finding soot in only one cylinder points to something with that cylinder. Does the engine run ok ( save the noise)? If yes this points to a connecting rod bearing or wrist pin, if no Check the valves see if a rocker arm is broken.

Might want to check your injector ( center one) and see if it is leaking or malufunctioning. This will have to be do by a shop. If the injector is faulty it should smoke some while running

If all is good up there.....
Drop the oil pan and start checking for play in the connecting rod bearings

Cheers

 

[OldBulldogger]

Okay - here is an update. The engine does seem to run fine, minus the loud tap/knock I am hearing. It revs up fine and returns like normal. I checked with a couple dealers and the service departments all said that starting it full throttle is okay as long as it is revved down right away. I checked the operator manual for cold weather start ups and it does say to open the throttle up. My fear was that being it was cold (25 degrees), would full throttle harm it? What would be the cause of the excess soot in one cyclinder? One mechanic mentioned wrist pins or a rod bearing. Most agreed that a faulty injector would cause it to run rough. One mentioned tappets. Most seemed to say if it was a crank bearing, they usually don't go that fast and I would see a drop in oil pressure. Any thoughts??