Steps to deal with weak pilot on old Jotul GF 300 DV Allagash?

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warmup777

New Member
Dec 30, 2021
23
bay area
Hi experts! I purchased an old Allagash (NG) that wasn't used much and then sat around for many years, and I vacuumed and blew out a lot of dust everywhere. After I had it installed (horizontal vent into a snorkel), the installers fired it up and it burned beautifully for about 20 minutes. But when they turned off the pilot and relit it, the pilot was feeble--two parts of the flame seemed OK but the third didn't reach the thermopile. Then they had to leave and can't come back for a while, ugh.

The pilot and burner orifices seem to be in great shape and are correct numbers for NG. After reading tons of posts, I'm trying to compile a sequence of steps to try to get this thing roaring again. I'd be grateful for corrections and additions of any sort before diving in!

1. Remove burner orifice and clean the gas feed tube behind it for spiderwebs (q-tip, pipe cleaner, wire, compressed air).
2. Clean holes in burner plate (small drill bit by hand) and gently knock/blow out any debris. When (if) burner lights, adjust air shutter to burn off debris.
3. Remove pilot orifice and clean behind it (compressed air? wire?).
4. Check tightness of screws where the thermopile connectors are attached to the valve's terminal block and make sure there's no visible corrosion.
5. Check thermopile terminal millivolt reading: (vDC, use TP-TH and TP screws on valve): With pilot lit and ON/OFF switch OFF, thermopile should be 500 plus or minus 25; with ON/OFF switch ON (burner on), should be around 220.
6. Check thermocouple reading (Disconnect thermocouple from valve; attach one clip on the enlarged "button" that seats in the valve & the other clip on the copper tubing an inch or so away from the button; ignite pilot & hold in pilot knob in to keep flame on): should be about 28mV.
 
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warmup777

New Member
Dec 30, 2021
23
bay area
Oh and:

7. Check to see that the two leads from remote receiver are properly connected to the valve. Test function of switch device by using a wire (jumper) to touch both connection terminals (TP/TH and TH) to see if the main burner comes on. If the jumper doesn't cause the main burner to come on, valve may be the culprit.
 

Lennox65

Member
Jan 29, 2021
131
New Hampshire
Oh and:

7. Check to see that the two leads from remote receiver are properly connected to the valve. Test function of switch device by using a wire (jumper) to touch both connection terminals (TP/TH and TH) to see if the main burner comes on. If the jumper doesn't cause the main burner to come on, valve may be the culprit.
All of those are great troubleshooting tips but your immediate problem is weak gas flow to your pilot. Until you fix that, none of the other steps are important.
 

warmup777

New Member
Dec 30, 2021
23
bay area
All of those are great troubleshooting tips but your immediate problem is weak gas flow to your pilot. Until you fix that, none of the other steps are important.
Thanks! I wanted to gather the possibilities so I had all the info in one place--with the exception of checking flow with a manometer, which I don't have and which I'd leave to the pros. To fix weak gas flow to the pilot, which of these steps would you suggest starting with?
 

Lennox65

Member
Jan 29, 2021
131
New Hampshire
Thanks! I wanted to gather the possibilities so I had all the info in one place--with the exception of checking flow with a manometer, which I don't have and which I'd leave to the pros. To fix weak gas flow to the pilot, which of these steps would you suggest starting with?
Check the pilot orifice. It is literally a pinhole and even a tiny amount of obstruction will reduce the flame.
 

warmup777

New Member
Dec 30, 2021
23
bay area
Check the pilot orifice. It is literally a pinhole and even a tiny amount of obstruction will reduce the flame.
That was the first thing I checked, if you meant unscrewing the orifice and making sure it was clean and free of obstruction. What I'm not clear on is how to clean below the orifice and down into the tubing, if that might be a worthwhile thing to tackle.
 

Lennox65

Member
Jan 29, 2021
131
New Hampshire
That was the first thing I checked, if you meant unscrewing the orifice and making sure it was clean and free of obstruction. What I'm not clear on is how to clean below the orifice and down into the tubing, if that might be a worthwhile thing to tackle.
Work backwards from the pilot. You can disconnect the pilot supply line and blow it out with compressed air.
Of course at some point you will need a manometer to verify correct supply pressure.
 
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yooperdave

Minister of Fire
Oct 26, 2010
1,221
Michigan's U.P.
Has the gas pressure been checked? (with all appliances running)

Has the vent screen on the regulator been checked to be clear of obstruction/debris?
 

warmup777

New Member
Dec 30, 2021
23
bay area
I spent some more time on the pilot and got it going again, yay! The pilot lights reliably with 3 flames coming out, the burner goes on and off as it should, and the turndown knob works. The pilot light is mainly blue with some flecks of orange at the tips. What I'm not sure about is whether the pilot flame looks right--would love it if you wise folks could weigh in on the photos.

Sorry for the photo quality, took them during the day with a lot of reflection! I've included the diagram from the instruction manual (which shows 1/8"-3/8" guidelines and seems to show the flame going past the thermopile?). I didn't play with the air shutter, which is positioned where the install guys left it.

pilot1.JPG pilot6.jpg pilot2.JPG pilot3.JPG pilot4.JPG pilot5.JPG
 
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warmup777

New Member
Dec 30, 2021
23
bay area
Has the gas pressure been checked? (with all appliances running)

Has the vent screen on the regulator been checked to be clear of obstruction/debris?
Good questions! I would assume the install guys checked the gas pressure, but if they end up coming back I will ask them to do this. I'm not sure what the vent screen on the regulator is, so the answer would be no on that one. :)
 
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warmup777

New Member
Dec 30, 2021
23
bay area
The millivolt readings were quite high--747 with pilot on and 295 with the burner on. After running a while, I turned off the burner and got 612, which is still high. So I'm going to slightly adjust the pilot screw on the valve and see if I can get them in the lower range, and also close the air shutter slightly to try to get the burner flames more yellow, and hopefully will be good to go (cross fingers)!