38k Protector backfires under load

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Tony
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Have had Generac 38k Protector propane fueled generator for 22 months. During routine self tests, the Mitsubishi 4 cylinder engine ran like a top. During the freeze in Texas a few weeks back we lost electric and it powered on. Under the house load it backfired every 60 seconds or so. Decreasing the load did not change the symptom. The guy who installed it (builder’s choice) charges time plus mileage for service calls and is 68 miles away. Works out to $400+ just to show up. I’m pretty handy with engines and would like to try and fix it myself. Sounds like a timing issue. Any thoughts would be appreciated. Tony
Chris
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What you need is a relationship with a qualified dealer if the unit is still under warranty.

Most times, backfires are related to the ignition system's components. The camshaft pickup, mag pickup, ignition wires, coil packs, etc. Fuel could also play a role if the pressure is wrong or the line sized incorrectly.
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Birken Vogt
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This could turn into a goose chase to fix. And it should be under warranty, correct? Best to get a qualified dealer on the job right away.
Mpsguy84
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Check on the outside of the gen frame right next to where the fuel pipe comes into the unit. There should be a sticker that has fuel information on it. If that sticker only has pressure and BTU/HR for natural gas then the unit was sold for use with the wrong fuel.

Propane has more energy per cubic foot than natural gas, so if the unit is set up for natural gas and is running propane the engine is being slightly over fueled and running rich. The back fire your hearing is probably unburned fuel igniting in the exhaust while under load. Something to check at least.
Tony
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Will do. Thanks
Chris
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The Protector series is field convertible up to 48kW (I believe that's changing with the 4.5L) so they will all be NG from the factory and require proper conversion to LP if needed. :cool:
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Tony
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Thanks Chris. How can you tell if the conversion has been done. Tony
Chris
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You would need to see which fuel jet is installed in the fuel regulator. Do you have an owner's manual for the unit?
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Tony
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Yes. For the Protecter series. Will look through it.Thsnks
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