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Spark Won't Light Pilot

Harry_6
Harry_6 Member Posts: 126
OK, I have a boiler with a spark ignition which only works occasionally. The boiler was out of service for several years, so as a precaution I replaced the ignition assembly (just a spark gap and pilot), high voltage wiring, pilot solenoid valve, etc. It has lit a couple of times, and the spark is reliably sparking, until the module doesn't sense flame and stops trying. It lights fine with a flame from a fire starter, but not the spark. Main burners are fine once the pilot lights, and the sensor keeps everything running. What think we? Pilot pressure? Weak spark? The spark position should be fine, as the assembly is fresh from the factory. Ditto, no debris or carbon.

Comments

  • Tim McElwain
    Tim McElwain Member Posts: 4,477
    Give a little more information and some pictures would help. What is the Make and Model of the boiler? Do you know how to measure microamps?
  • Harry_6
    Harry_6 Member Posts: 126
    I know how to measure microamps, but don't have the equipment to do so. The boiler is a Peerless series 63 from the late 90's, but I would think that's moot. There is a new spark igniter/pilot, new high-voltage cable and an older, but apparently operational, module controlling things. These parts could operate completely separate from the rest of the boiler.
  • Jamie Hall
    Jamie Hall Member Posts: 16,609
    Harry_6 said:

    ...The spark position should be fine, as the assembly is fresh from the factory. ...

    That ranks right up here with "famous last words". Check it.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • JUGHNE
    JUGHNE Member Posts: 8,687
    edited June 20
    You mentioned you replaced the pilot solenoid valve....is there a separate gas regulator for the pilot line?

    How about pictures of the entire gas train system?
  • Harry_6
    Harry_6 Member Posts: 126
    Yep. The pilot does have its own tiny 1/4" regulator right off the main and before its' 1/4" solenoid valve. The main burner part of the gas train is the common (for a boiler this size) 1" Regulator and two series V88 gas valves. Main burner fires up fine once the pilot lights. Spark sparks every time, just that the pilot won't always light. Plenty of pilot gas for me to light it by hand.
  • mattmia2
    mattmia2 Member Posts: 3,686
    Can you see where it sparks? if the insulator was cracked from the factory it might arc to the bracket somewhere.
    Shane_2
  • Shane_2
    Shane_2 Member Posts: 143
    mattmia2 said:

    Can you see where it sparks? if the insulator was cracked from the factory it might arc to the bracket somewhere.

    I would definitely check this. I have had brand new spark assemblies and even a brand new boiler do this.
    (Spark doesn't light pilot due to arc elsewhere)
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,247
    Hi, I'll add that if the gap is too small, that seems to affect the ability of the spark to light off the gas. I've had good success with widening the spark gap and getting gas to ignite consistently.

    Yours, Larry
  • Harry_6
    Harry_6 Member Posts: 126
    Thanks. All good suggestions. I inspected the assembly before installing it and it looks fine - no crack. Spark appears to be from the tip of the electrode to the deflector thing that spreads the pilot (technical term). All I can think is could the spark be too feeble or the gas pressure be too high/low? Haven't checked the pressure yet.
  • JUGHNE
    JUGHNE Member Posts: 8,687
    Just to point out that ground circuit from pilot to module is very important.
    May or may not be part of the problem.....seeing how the manual lighting works.

    Did you change or clean the pilot tubing?

    I have found that too high of pilot gas pressure lifts the flame off the burner.
    Too low is simply not enough flame.
  • Harry_6
    Harry_6 Member Posts: 126
    Pilot solenoid valve and tubing and pilot assembly all new. Ground was attached to the adjustment screw on the burner tube, which I don't trust. I'm moving it to the pilot bracket. I suspect the spark might be too weak, since I opened the valve on a propane torch and blew propane on the spark, and the torch wouldn't light either. I'm also going to get a new module, since I don't fully trust the old one. But I can light the pilot with the lit torch and it then stays lit and works fine. Ditto, once the pilot assembly is hot I can start the boiler and it lights right up, so there must be enough pilot gas to ignite from the hot flame spreader thingee (technical term).
  • HomerJSmith
    HomerJSmith Member Posts: 1,345
    NG or LP? Not all sparks have the heat value to ignite gas. The spark gap on a pilot assembly is generally set. Too small a gap-not enough heat value. Too large a gap-no spark.

    If you have gas present and spark you should have ignition. The ignition module should have unlimited tries if NG and limited tries if LP. What is the model # of the module?

    Weak spark could be the pilot assembly or the ignition module. The blue-er and brighter the spark the better.


  • Harry_6
    Harry_6 Member Posts: 126
    Natural gas. Pilot orifice should be right for NG. I suspect the module was not right, since it tries to light for under a minute and I have never seen it retry. Spark is like glorified static electricity.
  • JUGHNE
    JUGHNE Member Posts: 8,687
    Does the 24 Volt hold to 24-27 while sparking?
  • Harry_6
    Harry_6 Member Posts: 126
    Good question. I haven't checked that. I'll have to look.
  • Harry_6
    Harry_6 Member Posts: 126
    Replaced the module, moved the ground to the pilot bracket, and it's now right as rain.
    rick in Alaska
  • JUGHNE
    JUGHNE Member Posts: 8,687
    Did you move the ground wire first, before replacing the module?

    Or was it a defective module also?

    We appreciate the feed back, thanks for letting us know.