Tested fuel burning heaters today

[cranetruck]

I have used two different fuel valves on this heater and discovered this morning that the wiring to the solenoids had accidentally been switched last time one was installed, so the valve never turned on...

The wiring was corrected, but it still didn't ignite. I suspect that during the several "dry" starting attempts over the last few weeks, the wick may have been charred.
Removed the igniter section and found no wick, but a porous disc with a tab located 3/4 inch from the igniter coil. It's all pretty charred.
The igniter will be tested next....

For all the high quality parts in these heaters, it all comes down to a cotton or fiberglass wick for it all to work, crazy. Wonder how a spark igniter would work....(Multifuel flame heater style)...

Okay, the igniter glows red, so everything seems to be working. Now I'm thinking that it may take a lot longer to get the coolant heater going than the personnel heater....much less fuel delivery...I have no good reference for times to start the various heaters...

1530 hrs: After putting it all back together, I tested it twice this afternoon and each time it ignited (could hear rumble from the flame) after 110 to 115 seconds, the light came on after another 30 to 35 seconds.
However, it only ran for 15 seconds or so after which the overheat thermostat (??)
turned off the fuel solenoid... Same thing happened with and without the circulation pump running.
Need to check the thermostat. It is supposed to turn the heater off when the coolant gets to about 175°F.
Maybe there is some obstruction......

Next day, several test runs later:
Tested the thermostat and it appears okay. Measured the voltage at the "S" solenoid and it's not what's turning it off.
Every time I run the unit, the pattern is the same, flame can be heard 15 to 30 seconds later and the light turns on 30 to 40 seconds after that. It still only runs 10 to 15 seconds. The flame is snuffed out somehow....

Checked fuel pressure and it's 7 psi.
Voltage drops about 1 volt when igniter is on. Fan speeds up slightly when igniter goes off and switch is placed in "RUN" position.
Increased fuel delivery slightly, but no difference. Turned fuel delivery back to calibration setting (7 cc/min in "LO").
Removed cover on air intake end to improve air supply, no difference.

Based on my notes after six starting attempts, the time from "flame is heard" to flame detector switching is 35 to 40 seconds. This may not be enough for the combustion to become self sustaining.
Checking the TMs, this time period can be up to 200 seconds! As usual, the manuals don't explain what is supposed to happen during this time, but a re-calibration of the flame detector seems in order....

 

[cranetruck]

Adjusted the flame detector switch and started the heater.
Test 1 (08:20)
Time to flame ( I can hear the rumble from the flame): 20 seconds
Time to light (flame detector switch): 90 seconds
It now runs continuously, but smokes badly, so I turn it off after 1 minute. The purge time is about 2 minutes.

Test 2 (08:30)
Time to flame: 65 seconds (unit was properly purged this time)
Time to light: 105 seconds
Runs continuously , but smokes, so I shut it down after 1 minute again. Purge time about 2 minutes.

Test 3 (08:45)
Time to flame: 90 seconds
Time to light: 145 seconds

Runs continuously. Smokes again, but I keep it running, noted red flame at exhaust pipe, which may be normal, since the pipe is only 6 inches long. Lots of gurgling in the coolant hoses, which are getting warm. Noted coolant below the heater from a leak, can't see where it is.... turn heater off after 2 minutes. The purge time is very long this time, about 5 minutes...

The circulation pump is not turned on in any of these test runs, the coolant is moved by convection only, which seems enough to push the hot coolant through the hoses.

Well, looks like I'm getting somewhere, the flame detector switch adjustment seems critical to let the heater warm up.
Need to find that coolant leak now....

Tested the heat exchanger under pressure (about 45 psi) and found the hose barb to be leaking. Put the thing back together and it's now ready to be be installed on the truck again.

The heat exchanger holds 1/4 gallon (1 liter) of coolant, which may contribute to the time it takes for the flame to become self sustaining, up to 200 seconds according to one TM.

 

[cranetruck]

Checked the calibration of a Benmar fuel valve today for a break in the routine and found it working right off the bat, something that the South Wind heaters never did (five out of five have needed work).
If the rest of the heater works as well, I'll be swapping it for the South Wind unit, now on the truck.... They are both 30,000 BTUs.

 

[cranetruck]

It's one of those days, cool and overcast, so it's not too fun to work outside. Took apart a Benmar heater and noticed that it doesn't use a wick, like the Stewart & Warner units, but has a ceramic block with the igniter running right through it. I kind of like that, should make it more reliable, it's soaked by the fuel and the blower action vaporizes it, which is then ignited by the igniter.

 

[doghead]

Can you post a picture of the Benmar ceramic block?

 

[cranetruck]

Can you post a picture of the Benmar ceramic block?

This one is cracked, the heater has a big dent in it, so it's not surprising, I still have a good unit, though.
The disc is item #41 in the diagram.
The Benmar heater model number is AP-3050 and the NSN is 2540-00-186-2558

 

[cranetruck]

Tested the Benmar heater for the first time in six or so months and noted smoke in the hot air outlet...not good. Took the whole thing apart and found corrosive damage by the combustion chamber. The double walled structure that feeds air into it is rusted thru in several places.

Question: Has any of you experience with any high temperature putty?

 

[gimpyrobb]

Just find an hvac guy and have it brazed.

 

[cranetruck]

So I took the best parts from the two Benmar units I have, cleaned everything and re-installed it on the truck. It was running after 2 minutes and 40 seconds and I let it run for 15 minutes. No smoke in weird places....The shut down sequence took 1 minute and 45 seconds and it smokes at this time when excess fuel is burned off.

Edit: Added pictures to complete the entry.

 

[cbvet]

Thanks for keeping us updated Bjorn.
I got too busy & a little bit discouraged while working on mine last fall, so I will make use of the info you share when I get back to them.

 

[Coldfusion21]

Thanks for the great logging of your work. I dont have a MV much less a fuel powered heater but i think its great that you take the time to share all that info. When the time comes (and it will) that i have an MV and want to mess with the heaters, i will surely appreciate this thread as a reference.

 

[cranetruck]

Thanks for keeping us updated Bjorn.
I got too busy & a little bit discouraged while working on mine last fall, so I will make use of the info you share when I get back to them.

Know what you mean, just look at the dates of the above postings and you'll see me doing the same.
Still haven't gotten into the coolant heater after I left it back in October...

 

[steelsoldiers]

We'll all be furiously working on our heaters in another few months! My kit is complete except for the supply hose that runs from the pump to the heater. Mine was leaking all over the heater exhaust and making a nice smoke screen. I got a new one made at NAPA in 10 minutes using the old one for a pattern. I haven't gotten it installed yet because I have had bigger fish in the pan trying to get the engine completed!

Good luck with the coolant heater. I am glad you got the smoke in the cab taken care of, Bjorn.

 

[Boatcarpenter]

OK, been reading a lot about these heaters and a TM is referenced but I can't find the number. Any help?
BC

 

[ida34]

A little late but the -30 manuals for various trucks have maint instructions.

I got three heaters of the B variety from M1075 with newer solid state circuitry. They are NOS with calibration tags and all. They also came with a mounting fixture and flange welded on the exhaust pipe. I had been working on my old heaters also. Got one control valve to flow by spec. I plan to try it on the air heater to confirm its operation. If it works good I will put the valve on my NOS coolant heater. It took parts from both of them to get one working fuel control valve. I also have a M151 fuel heater and it has a smaller connector so I can't use the standard control box. I will take the connector off one of the other heaters to check the operation of the M151 heater. It also has a port for a thermostat which just has a jumper in it. It also has a separate output for the fuel pump that I have not seen on other heaters. It is nice to have a small victory. BTW the fuel control valve was about 18.3 CC on high and 6 on low. I had to pump it up a little to get the low setting closer to acceptable but did not want to go too high on the high setting. Crossing my fingers on this.

 

[jas67]

I wouldn't mind having such a thing on my Powerstroke-powered F-350. It'll start when it is cold, but I prefer to use the block heater, as it runs much more smoothly after startup if I do. Of course, the block heater isn't an option at work for the drive home. It would be nice to pre-heat the engine before leaving for home at night.

 

[ida34]

You might be able to rig one up but these operate on 24 volts. Another problem is room to mount it. I wonder if the powerstroke would have enough room to mount one under the hood. If you have one of the older body styles I would think it would fit with some work.

This link is for a company that sells new 12 volt diesel coolant heaters.

 

[cranetruck]

In the process of resurrecting an SW heater and I would like to post my procedure for draining fuel from the combustion chamber here.
If the unit doesn't ignite on time (after about a minute) and you continue to hold the start switch in "start", fuel will begin to build up at a rate of more than 1/2 an oz per minute. This accumulation of fuel can cause problems and must be removed before another attempt is made to start the heater. The TM will just tell you to replace it...not what we do, of course.

Instead of taking the heater apart to drain, remove the flame detector switch, shown on the table to the left of the heater in the image below and insert a piece of tubing into the opening. Next, start siphoning and let drain.
When you can't hear any more sloshing, consider the heater ready for another try, just reinstall the flame detector switch.