I am cleaning up a recently-acquired Coleman 639. Stripping the generator I find that the pump tube has two springs/coils in it - one inside the other. I battled a bit to get either coil out but finally managed to extract the inner coil with the pricker needle firmly stuck inside it. The outer coil remains stuck in the gennie tube. I've soaked the inner coil and pricker in caustic soda and seem to have got rid of most of the carbon build-up but still cannot remove the pricker rod from the coil. However when I put the inner coil back into the tube, it slides fairly freely inside the outer coil so, presumably, the pricker needle will be able to do its job. So, my question is: is it essential that the pricker rod slides inside the inner coils or will the generator still work properly if the one coils slides inside the other? I ask the question not to avoid work/effort but because I am anxious to avoid recent misadventures where I applied force and bent coils out of shape which were then very difficult to reassemble. Peter
Hi Peter, a good way to clean the inside of the generator is to burn out the carbon. Remove the jet and if at all possible the pricker rod, place the generator on a dry clay brick and have a dish of cold water handy. Heat the centre 3/4 section of the generator to dull cherry red for 10 -20 seconds with a blow torch and roll it off into the water. Rinse and repeat. This will burn away and loosen the carbon and enable you to remove the brass spiral(s) without significant damage. You can do the same to the individual spirals too but be careful not to overheat and melt them. The brass tube and spirals will be annealed and very soft so care is needed not to deform them when e.g. holding with a pair of pliers. Being so soft they can easily be re-formed using a rod or screw driver of the correct diameter. Any remaining carbon ash can be removed from the spirals by rotating them through fine steel wool and the tube can be cleaned out with a copper gun brush, drill bit or round file. Clean the flared end of the tube inside and out with the steel wool too to ensure a good seal. Rinse the tube to remove any debris or dust before reassembly. Keep the flame far away from the pricker needle! Just a hint of flame will burn it away and you will then have to buy a complete new generator. Packrat do have stock, by the way.
Many thanks, Phil. I followed your detailed advice and it worked a treat. Decoking enabled me to get the stuck coil from the tube and I then applied the heat treatment to both coils and cleaned out the tube. Best of all, I succeeded in reassembling the gennie and it works! Peter
Another question, if I may: should there be a seal of some sort in the boxnut on the control knob stem? Since I cleaned up my the lamp, a fuel leak has developed at the boxnut when the lamp is pressurised. I notice that there is no rubber O-ring there although there does seem to be a seal of sorts at the bottom of the boxnut. Initially I thought it was a build-up of grease but it won't clean out easily. I now suspect that it may be a graphite seal/ring (although, if it is, this one is disintegrating). It would be nice to know what I'm dealing with before I do it a mischief . Peter
There is a graphite ferrule inside the box nut sealing against the valve stem. You can pinch up the box nut until the valve stem becomes quite hard to turn and then back off a tad. That should re-shape the graphite and make it seal again.
I followed your advice and the problem is solved. Many thanks, Phil. However in trying to clean out the supposed 'grease', I scratched away some of the graphite ferrule with the result that I have had to tighten the boxnut almost to the end of its threads. So, I suspect that a new ferrule will be needed in the foreseeable future. Are these available and if so, where? Peter
You can use any flakes of graphite seal material you may have. Stuff it in and tighten up. It forms a ferrule. I will send you a strip of graphite sheet in your parcel.
Hold on, I think on the 639 the graphite ferrule is around the shaft inside the valve body behind a brass spacer, which is pushed in by the box nut. So to refurbish the graphite seal, undo the box nut, partially unscrew the valve stem, move the spacer out of the way, screw in the valve stem, stuff in the graphite, replace the spacer, then replace & tighten the box nut.
The above instructions are correct for the 237 but the 639 has no spacer between the box nut and graphite packing. On both models there is a brass retainer and a wire circlip on the other side of the seal. In the photo below, a new graphite seal has been put onto the shaft of a 639:
