Fixing Hapy Furnace (part 2)

Picking up where I left off the last post, Hapy has an operational furnace again.

Fuel Pump Swap

As I mentioned in my last post, the fuel pump which originally delivered with the heater/furnace would not work when I tried to bring things back to life. I splurged and bought a more expensive "quiet" model for $50US rather than another standard pump for $20US. I figured quieter or not, the more expensive pump may have better parts in it, and it may last longer whether it is quieter or not. Or it was just a marketing gimmick and I got took. Let's chalk it up to the cost of an experiment.

The old fuel line path was relatively simple. The "hard" (clear but firm plastic) lines that delivered with the furnace had short (50mm / 2-inch) stretches of fuel hose between them and the pump. The pump was suspended from a cross beam by the included rubber mount held in place by a single sheet metal screw. After a few turns with a screwdriver, the pump was on the ground. A few more and the fuel lines were removed from it. The supply fuel line started dripping fuel after a few seconds, so I caught it with a pan. The line on the pressurized side was completely empty, so no drips. I simply reversed the removal: added the rubber mount from the supply end of the pump, added the supply fuel line, suspended the pump from the cross beam and then added the pressurized-side line.

Prime and Fire Up

The Afterburner has a control page where you can direct only the fuel pump to fire up. This allows you to get fuel all the way to the furnace without the glow plug turning on (drawing the battery and maybe burning out the glow plug). I had not connected the pressure line to the furnace, but I wanted to clear the lines of any bad fuel, so I moved the pan under the dangling hardline and triggered the Afterburner to prime. Within a minute of the prime starting, fuel started spurting out the end of the line. It took longer than I expected it to, but perhaps that is an indication of how little fuel these units actually consume. Once the fuel leaving the pressure line looked like the fuel supplied at a filling station, I stopped the prime function and connected the hardline to the fuel hose dangling from the furnace.

While the pump was slightly larger than the original, it did not seem much quieter during the prime. Of course, I hadn't heard it pump in a couple of years, and memory is a funny thing. I do recall that when the furnace was running, I could hear the tick-tick-tick of the fuel pump over the whoosh of the furnace. With this in mind, I set the furnace to start. I did not want to consider the experiment with the new thicker, dedicated wiring yet, so I left the battery tender hooked up. At no point did the battery fall below 13.5V so either the tender was working hard, or the new wiring is a hit.

Regardless, the glow plug got lit, the fan started spinning and after 2 or 3 minutes the furnace ignited. This felt like a considerably longer period of time than before. Perhaps the priming was incomplete and I needed to prime again after connecting the hose to the furnace. Perhaps it took time to ignite simply because it had been so long. Once it ignited, a huge plume of smoke poured out of the little muffler. There was virtually no wind, so the cloud grew and sat slowly obscuring first the rear end of the bus and slowly 2/3 of the bus before a light breeze broke it up. After a few minutes, the cloud dissipated and the exhaust emission was reduced to nothing. All that remained was a light smokey haze inside the bus. I regret not taking a picture of that.

Noise Observations

While the temperature inside the bus slowly crept up from 55*F (13*C), I noted the noises. I could only hear the fuel pump ticking inside the cabinet where the furnace is located and even then, only when I stuck my head into the cabinet. I think the pressurized line is transmitting it. I stuck my head into the rock-n-roll cabinet above the spot where pump is actually installed and could not hear it. Maybe this new pump is quieter. Then, I moved outside where in the past I could clearly hear the pump from several feet away, even from the passenger-door side. I could not hear it, but I could hear the furnace whoosh. Of course, my muffler-ing of the furnace is different this time, having removed the second small rectangular muffler and the motorbike muffler. Perhaps the pump is no quieter, but the furnace is that much louder. To determine if the muffler configuration is a variable, I decided I will conduct another test at a different time, after re-attaching the other muffler bits. I had thought about bringing them along for while-parked use, and maybe I will need to, out of respect for our festival-going neighbors. In the past, I took decibel readings, but they were for while the furnace held a temperature, not during temp catch-up (full blast).

I will continue to experiment with noise readings and post if I find any readings are different than they were 4 years ago. I expect that once I put the extra rectangular and motorbike mufflers on, the readings will be what they were before. The only real mystery to me is whether the fuel pump can be heard over it. At this point, though, the pump seems significantly quieter.

Thanks, as always, for following along-