3B glow plug physically won’t fit into hole (1 Viewer)

[John in Utah]

Doing glow plugs and a compression check on my 3B since it’s had a harder time starting this winter than last, I found someone had put the wrong plugs in it. The correct Y-147T plugs are quite a bit long than the Y-118T-1 old plugs:

I didn’t think much of it until the #4 plug won’t even catch threads in the hole. It will thread into the other 3 cylinders just fine though. Could this be why someone used the shorter than stock plugs?

Ive read of VW or merc diesels having issues with carbon buildup in the holes and needing reamed out. Could I just dump some diesel down there and hope to loosen any up? I thought the plug goes down into the pre cup so I’m pretty scared about forcing it down in there.

 

[roscoFJ73]

Try diesel or some kind of solvent. They all have a carbon build up problem if the maintenance on the injectors is let go.
It might be job for a machinist if you cant get the thread to start.

 

[Yellowknifer]

Are you superglow? I'm using a Y-197R plug in my superglow 3B.

 

[John in Utah]

Are you superglow? I'm using a Y-197R plug in my superglow 3B.

No just a 12v Wilson switch. This is a motor swap so I don’t have any of the original glow equipment.

 

[roalco]

I have had carbon build up in the glow plug hole before, and if I remember correctly, I used slightly undersized drill bits (by hand) to gently ream out the carbon, without damaging the iron head. If you lightly grease the drill flutes, most carbon chips will stick in there and can be extracted when the drill bit is withdrawn. Gently, gently.
Btw, my 12volt cruiser originally had super glow, but unfortunately the initial heating circuit in the controller failed, so I put a momentary contact switch bypassing it (ala "Wilson" switch), but still have the reduced voltage secondary heating circuit active. Have used a number of glow plugs, and find that the modern Bosch GPT-214 (6v, .3ohm) are the perfect length, and are closest to the original heating time, I use 5 seconds on the switch (once, or perhaps twice, if it's very cold) and it starts very well and Iget good long life from the plugs (last set has been in for at least six years).