scottatbhm
Hello and thanks in advance for any assistance.
I purchased this unit, serial number 4133249, about 5 years ago. A neighbor who had recently completed Generac school installed it for me. Natural gas fueled with about four feet of fuel line from meter. It ran like a charm for about 1 year and then started shutting down with a over speed alarm. Engine would crank and run about ten seconds then shut down. My neighbor tried to repair several times by adjusting the throttle and performing electrical tests.

About three years ago I moved and brought the non-working generator with me. I'm now troubleshooting it myself. The gen. is now LP powered by a 20 pound tank connected with a two foot black hose about 1 1/2 inches in diameter. The gen. carnks and runs about ten seconds and then shuts down. The green LED and all four red LEDs flash the entire time it is running. The reds flash faster than the green one.

I performed diagnostic test 70 with a Fluke 87 III dmm. Step 5, wire 66A continuity passed with zero ohms. Step 6, wire 55 continuity passed with 1.6 ohms. Step 9, wire 66A voltage test failed with .02 volts. Step 10, wire 66A HZ test failed with zero HZ. The only way I could see to test wire 66A at J1 was to jam the test lead into the connector where the wire 66A came in so I can't guarantee I was making good contact, but I think I was. I proceeded to test 7.

Test 7, step 7, power winding test wire 11 to wire 22 passed with .2 ohms. Step 8, power winding test wire 33 to wire 44 failed with a open circuit reading.
Step 9, battery charge winding passed with .15 ohms.
Step 10, engine run winding passed with .1 ohm.
Step 11, power winding-sense leads was .3 ohms and I could not find a reference value for this test.
Step 12, excitation winding passed with 1.6 ohms.
Step 15, stator wire 11 short to ground failed with 3.1 ohms.
Step 16, stator wire 33 short to ground failed with 3.0 ohms.
Step 17, pin 1 short to ground test passed with open circuit.
Step 18, pin 3 short to ground test passed with open circuit.
Step 19, pin 5 short to ground test failed with 2.9 ohms.
Step 20, pin 7 short to ground test passed with open circuit.
Step 22, stator wire 11 and 33 shrt test failed with .5 ohms.
Step 23, wire 11 and pin 1 short test passed with open circuit.
Step 24, wire 11 and pin 3 short test passed with open circuit.
Step 25, wire 11 and pin 7 short test passed with open circuit.
Step 26, wire 33 and pin 1 short test passed with open circuit.
Steps 27 - 31 all passed with open circuit.
Steps 33 - 36, control panel wire continuity all passed with .3 ohms.

I would really appreciate an interpretation of these test results. I'm not very knowledgable about generators. I'm thinking the stator windings have probably shorted out.
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Skip Douglas SkipD
Your problem is trying to run the generator from a very small tank. There needs to be a minimum surface area of the liquid propane for it to convert to gas fast enough to supply the generator.

Download and open this [URL="http://www.mygenerac.com/PublicPDFs/0172610SBY.pdf"][U][COLOR=Blue]Generator Sizing Guide from Generac[/COLOR][/U][/URL] and turn to page 9. Your generator draws something on the order of 125,000 BTU per hour at full load. You need to look on the chart for the size tank you need based on that figure plus the lowest outdoor temperature at which you want the generator to operate. You'll find that you need at least a 100 gallon tank, not the four-gallon tank that you're presently trying to use.

You will also need proper regulators to make the package work properly. If you have run full tank pressure to the generator, you have probably damaged (or destroyed) the demand regulator in the generator.

It sounds like you have additional problems, but you need to resolve the fuel problem first before you can really go any further.
Skip Douglas
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scottatbhm
Hi Skip, thanks for the reply. I purchased and installed the correct LP gas regulator. The engine starts and runs fine until some sensing circuit shuts it down after about 10 seconds. There is no load on the generator that would require higher rate of fuel consumption. And as you pointed out, full tank pressure is more than adequate to supply the regulator.
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Skip Douglas SkipD
scottatbhm;8521 wrote:
Hi Skip, thanks for the reply. I purchased and installed the correct LP gas regulator. The engine starts and runs fine until some sensing circuit shuts it down after about 10 seconds. There is no load on the generator that would require higher rate of fuel consumption. And as you pointed out, full tank pressure is more than adequate to supply the regulator.
What I was trying to get across is that the liquid propane in a 20-lb propane cylinder quite probably cannot convert to gas fast enough to keep the generator running. The colder the tank is, the worse the condition is. The issue is the surface area of the liquid in the cylinder. More surface area provides the ability to convert a greater volume of liquid to gas.

In order to prove whether or not it is even possible for the generator's engine to run with the 20-lb cylinder, measure the gas pressure being fed to the generator's fuel inlet fitting. It should be between 10 and 12 inches of water pressure (0.36 to 0.43 pounds per square inch) both with the engine off and with the engine running at any load up to full load. You'll need a gauge (typically a water manometer) and fittings to be able to read this pressure.

Additional - your generator, at half load, would consume .82 gallons of liquid propane. At full load, your generator would consume just under 1.5 gallons of liquid propane per hour. A 20-lb propane cylinder only holds about 4 gallons.
Skip Douglas
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scottatbhm
Thanks Skip, I understand what you are saying but I don't think that is the problem here. The problem started when the generator was connected to natural gas and had been working well. Something in the sensing system was making it report overspeed and shutting it down. The propane now is to just troubleshoot the system before I go to the trouble of running natural gas to it.
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scottatbhm
Skip, I researched your concern and it is very valid at high load conditions. The rate of fuel consumption from a 20 pound tank is so great that the propane will eventually freeze in cold conditions. It's 73 degrees here and the gen. has zero load. Thanks again for your help.
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scottatbhm
I forgot to mention that I replaced the air filter bellows, it was falling apart.
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d11gnccer
Aside from running on a small tank. The flashing green LED is indicating no utility sensed and all Led's flashing means the excercise is not set. Ignore them for the time being if you are switching it to manual and still getting an overspeed shut down. What is your frequency during start up and just before the generator shuts down? Try it again and see what you voltage readings are. Have you adjusted the governor per manual specs?

Edit-Sorry. Read you post again and it looks like you were getting zero volts and zero HZ.
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Zapme
scottatbhm;8517 wrote:
Hello and thanks in advance for any assistance.
I purchased this unit, serial number 4133249, about 5 years ago. A neighbor who had recently completed Generac school installed it for me. Natural gas fueled with about four feet of fuel line from meter. It ran like a charm for about 1 year and then started shutting down with a over speed alarm. Engine would crank and run about ten seconds then shut down. My neighbor tried to repair several times by adjusting the throttle and performing electrical tests.

About three years ago I moved and brought the non-working generator with me. I'm now troubleshooting it myself. The gen. is now LP powered by a 20 pound tank connected with a two foot black hose about 1 1/2 inches in diameter. The gen. carnks and runs about ten seconds and then shuts down. The green LED and all four red LEDs flash the entire time it is running. The reds flash faster than the green one.

I performed diagnostic test 70 with a Fluke 87 III dmm. Step 5, wire 66A continuity passed with zero ohms. Step 6, wire 55 continuity passed with 1.6 ohms. Step 9, wire 66A voltage test failed with .02 volts. Step 10, wire 66A HZ test failed with zero HZ. The only way I could see to test wire 66A at J1 was to jam the test lead into the connector where the wire 66A came in so I can't guarantee I was making good contact, but I think I was. I proceeded to test 7.

Test 7, step 7, power winding test wire 11 to wire 22 passed with .2 ohms. Step 8, power winding test wire 33 to wire 44 failed with a open circuit reading.
Step 9, battery charge winding passed with .15 ohms.
Step 10, engine run winding passed with .1 ohm.
Step 11, power winding-sense leads was .3 ohms and I could not find a reference value for this test.
Step 12, excitation winding passed with 1.6 ohms.
Step 15, stator wire 11 short to ground failed with 3.1 ohms.
Step 16, stator wire 33 short to ground failed with 3.0 ohms.
Step 17, pin 1 short to ground test passed with open circuit.
Step 18, pin 3 short to ground test passed with open circuit.
Step 19, pin 5 short to ground test failed with 2.9 ohms.
Step 20, pin 7 short to ground test passed with open circuit.
Step 22, stator wire 11 and 33 shrt test failed with .5 ohms.
Step 23, wire 11 and pin 1 short test passed with open circuit.
Step 24, wire 11 and pin 3 short test passed with open circuit.
Step 25, wire 11 and pin 7 short test passed with open circuit.
Step 26, wire 33 and pin 1 short test passed with open circuit.
Steps 27 - 31 all passed with open circuit.
Steps 33 - 36, control panel wire continuity all passed with .3 ohms.

I would really appreciate an interpretation of these test results. I'm not very knowledgable about generators. I'm thinking the stator windings have probably shorted out.


The 4389-3 has the GT 760 motor which is a one cylinder engine. The unit I have 4390-3 has the GT 990 motor which is a two cylinder engine. I've hooked up my unit to a 20# propane tank (BBQ grill type) placed it under a 80% load using a 1 inch hose, 5 feet in length for 45 minutes (45-50 amps on a 240 volt leg) and the unit ran perfectly. Although after 25 minutes the bottle froze up so much that it froze to the concrete slab...no shit. SkipD has a valid point on the fuel supply but, that will NOT affect the unit in 10 seconds.
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scottatbhm
Thanks Zapme, I've read about others running them off 20 pound tanks too. And the 4389-3 has the even smaller GH-410 engine.
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