IH424 pre-combustion chambers

[stevej]

Previous owner had engine work done on 424 diesel but never got the thing running.  Getting close to getting it running but ran into a problem with glow plugs.  It appears that the pre-combustion chambers were not aligned properly when they were installed.  So the glow plugs are partially obstructed when installing.  Visibly, looking into the glow plug hole, it is easy to see that the chamber hole is not aligned with the head.  The problem is that the glow plugs show definite contact marks when removed and one even has its glow loop bent.  With the plugs installed, because they are making contact with the chamber, they are all shorted to ground per ohmmeter readings.  The very second the glow plug button is depressed it immediately goes bright red.  I have been careful and so far have not destroyed anything, but I need to figure out what to do.  I removed the head.  Now for the questions.  Can I simply go down into the glow plug hole with my Dremel tool (it has the flex cable option) and simply grind out the interference or do I have to have the chambers removed and reinstalled properly?  At least 3 of the holes are messed up.  Also, how do you remove a chamber?  I tried, not very hard, to pry in the T-slot in order to pop it out but it didn't seem to give any so I quit.  Any information would be a big help and thank you for your time.

[J-Mech]

1 hour ago, stevej said:

Can I simply go down into the glow plug hole with my Dremel tool (it has the flex cable option) and simply grind out the interference or do I have to have the chambers removed and reinstalled properly? 

No, no, no.  You cannot just grind them out. Good night.  Yes, you have to remove them and properly orient them.  

I've not ever knocked those out, but I looked up the part.  Looks to me like the go out the top.  Drive them up from the bottom.  If you ruin one, looks like new ones are about $20. 

[jimb2]

There is a service manual for the IH BC and BD engines online at link below that mentions a special tool to remove the pre-combustion chambers.
There is also a kit that is available to replace those old glow plugs with a new fast heat glow plugs used in Mercedes 240D, see link below.

http://www.tractorparts.com/PDFs/IH_ENGINE_IH_BC-144_BD-144_BD154_ENGINE_SERVICE.pdf

190D 200D 220D Early 240D Fast Glow Plug Upgrade w / Manual Push Button Control | Product | MercedesSource.com

[stevej]

Tackled the head problem again this morning.  Took it to an engine machine shop and they weren't familiar with the 424 but felt strongly that the pre-combustion chambers were driven out by going down through the injector hole.  I was skeptical after looking at photos online and agreeing with J-Mech.  Went back to the shop and got a brass rod and hammer and drove one of them out by going upwards through the injector hole.  It actually came out fairly easily.  Cleaned it all up with a bench mounted wire wheel and a wire cup mounted in a drill.  After cleaning is up I re-inserted it into the hole and discovered that there is no alignment adjustment.  The chamber is cast/machined where it can only go in one way and self-centers.  And if you try to turn the chamber it simply 'cants' up on one side or the other and no longer lays flat with the head surface.  So there is no alignment tool needed, it would be useless.  

Now that the removal and alignment issues were resolved it was time to check the alignment of the threaded hole in the cylinder head for the glow plug and the the alignment of the hole in the pre-combustion chamber.  It was immediately obvious that the problem still existed.  Looking in the glow plug hole with a pen light it was easy to see that the chamber hole is not lining up with the glow plug hole.  That is a big problem because there is nothing that can be adjusted to compensate for the misalignment.  And yes, the chamber was fully seated with the face lying perfectly flat to the main combustion chamber. 

I screwed a glow plug in and sure enough I could feel it contacting something when it was almost fully inserted.  A quick check with a multimeter and the glow plug was a dead ground, no matter where you measured it.  So I backed the glow plug out a bit where no contact was detected and the meter immediately indicated that the ground cleared.  No doubt whatsoever, the glow plugs are making contact with the 'isolated' part of the glow plug thereby grounding it out.  

Since there is no way to do anything mechanically to the cylinder head or the pre-combustion chamber mounting I simply looked into the holes and determined which areas of the chamber were interfering with the glow plugs. The material that was interfering was the bottom section of the chamber.  In order for that material to not interfere with the glow plug the chamber would have to be installed deeper than was possible.  I then removed the chambers and using my Dremel tool I removed the material necessary to clear the grounds.  All four cylinders are now ground free and the head is fully reassembled and ready for installation.  Hopefully before the end of the week.  

I took to heart what J-Mech had to say about not modifying the chambers but there was no other choice short of ordering a whole new set of chambers hoping that they would be different that the ones the machine shop put in there about 4 years ago.  I suspect that there is a good chance that a new set would work because I believe that these may have been some mis-machined, cut rate parts.  So for now I am going with it the way it is.  

The strange part about this is that the hole in the pre-chamber is larger than necessary for the glow plug.  The holes are also a bit oblong top to bottom.  Had those chamber holes simply been about 1/32" lower on the pre-chamber body everything would have worked out without issue.  That is why I suspect a quality control issue with the chambers.  

Thanks both of you for the information.  I am sure as this project proceeds I will likely run into more stuff that I will need a bit of help with so you will likely see me here again.  

[stevej]

On a bit of different note I have to replace the fuel shutoff pull cable since the original one, after sitting outside for 4 years, was froze solid.  I Kroil-ed the cable for about 4 days but simply could not get it to loosen up.  Ordered a new one that is vinyl jacketed, hoping it would last longer.  The new one even has "Pull to Stop" printed on its red knob.  With all of that said, the problem I have is with regard to the working end of the cable.  I can see no fastener, attachment or anchoring hardware to solidly secure the far end of the cable where it connects to the injector pump's shutoff valve.  The shutoff valve is connected to the 'accelerator' arm of the injector pump with a spring but I am not quite sure how the 'choke' cable affixes to the engine block or the pump.  It seems to me that the working end of the cable - the jacketed part - should be anchored.  I tried to look at web photos but can't determine much.  Some of the photos show a solid rod connected to the shut off valve.  Mine is definitely intended to be a cable.  Do you have any reference or observation regarding this issue?  Thanks again.

[J-Mech]

Sounds like you did the right thing on the pre-ignition chambers. 

[Rod Smith]

Stevej,

The other option that may have worked would be the installation of the fast heat, pencil type glow plugs jimb2 linked in his post.  Depending on the contact point, the pencil type glow plugs are more narrow than the old champion ch28 loop style plugs that come from the factory and (in my experience) are likely not to make contact with the precombustion chambers, along with a whole host of other benefits.