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Diesel Workshop Heater 1st Year Service.
Joules:
The workshop heater has done about 13 months in the workshop and started to smoke prior to ignition since about December. I figured it was time to strip it down, de-coke and check the vaporising mesh. The dissasembly was pretty straight forward apart from damaging the gaskets, they are little more than fireproof cardboard. The combustion chamber gasket was repaired with high temperature silicon used for stove installation. I also used this as a replacement for the fan housing gasket, being very cautious not to get silicon on the compressor fan.
Considering my heater is mostly at idle the heat exchanger shows little in the way of soot. Since I had it apart I used a toothbrush to clean out what was there, but it wasn't much. The exhaust pipe is coated, but in no way chocking up. A snag I had not using the original gasket on the fan housing was that the motor shaft is only 1mm clear of the rear of the combustion chamber, you can see the mark the shaft made... This was due to the clearance the gasket gave. A quick job with the Dremel got 1.25mm off the shaft and regained clearance using the silicon gasket. If I had used silicon on the combustion chamber it would have had the correct clearance, but a little extra won't harm here.
What I did find interesting was the mesh present in the combustion chamber (top of picture), it must have started breaking down and not acting as a wick anymore, some mesh is present inside the cavity around the wall, so I guess this also helped in vaporising fuel and aid ignition once hot. The vaporising meshes sold are just wound and pushed into the port where the heater goes, you don't seem to get one with the heater as none was present on mine, only the mesh in the combustion chamber. It's not a problem to make your own, mine shown here is fine mesh rolled on a 6mm drill to form it. This is then pushed into the port using the heater to seat it, screw the heater in by hand to set the mesh in position and be careful no wires come loose from the mesh and get trapped in the thread.
My mesh was rolled from a piece 18mm x 30mm and took a couple of minutes to make. The heater can be reassembled and installed back, oh worth swapping over the fuel filter whilst your at it, mine had got pretty funky after a year. My heater is back in service, I altered the position of the external fan a little to stop it rubbing as it did on occasions, the mouldings aren't that great and you can see quite a bit of runout towards the blades where the fan has relaxed after moulding.
So if your heater has started smoking, it's definitely time to fit, or replace the vaporising mesh.
Joules:
Well that was a FAIL....
Yesterdays tests went well, no smoke and heater started no problem. Today, loads of smoke and failure to light. Scratching my head, wondering if the glow plug was on its way out. Nope, the mesh I installed had choked up and held enough fuel to chill the plug below ignition. Kind of explains why the mesh WASN'T around the plug. :bang:
Sooooo, pulled the mesh and the heater worked fine, other than a little smoke and for longer as it cleared the residue out the heat exchanger.
My mesh was a big fail, so wondering where it goes and looking at the amount of residue, my mesh may be too fine. I guess you are supposed to somehow jam it into the combustion chamber, but no way I can see you can get a 9mm roll of courser mesh into that cavity. Looks like I live with a little smoke at the start for now.
awemawson:
What determines the volume of fuel supplied to the burner - is there a calibrated jet? Perhaps it's over fueling?
Or conversely under airing?
Joules:
Just the blower and pump control the fuel air mixture, no jet. It relies on a trickle of fuel down the glow plug combusting on contact, once the combustion chamber is hot the fuel vapour spontaniously combusts and keeps the mesh in the combustion chamber glowing, bit like a hot bulb engine. The glow plug is turned off once the temperature raises above a set limit. Too much mesh in contact with the plug just soaks away the heat and holds liquid fuel, this fuel then just chars, but doesn't ignite causing the carbon build up. A bit of smoke at the start is the lesser of two evils for now. Looking at the picture you can see the section above the glow plug tip is discoloured but no carbonised fuel. That is why the glow plug is turned on and the fan ramped up at shut down, to clear residue for the next run.
mc:
I was wondering how your home made mesh would hold up.
I've only ever serviced Eberspachers, but their mesh is more like a metal mesh version of an air stone.
Actually, having just done a search trying to find a photo, this page shows one unwound, and they're actually five different layers - https://www.letonkinoisvarnish.co.uk/d2_d4_service_2.html
I have been considering one of these Chinese heaters for the workshop, but I've not been cold enough this year to finally spend the money. However, I'm lead to believe this facebook group is the best place for finding spare parts for them - https://www.facebook.com/groups/146837062640024/
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