The symptom: It dies after about 20 minutes and usually wont restart. So here's a basic test list anyone can do with the right tools.
Tools needed: A good 12vdc Test light, a digital volt ohm meter and an Infrared Thermometer. ( ever been to one of my seminars? LOL)
Theory of how it works.
Most GAS genny's work on this principle. There are 3 "shutdown" safeties. 1) Low Oil 2) Overheat and 3) Low oil pressure. Add number 4 as a bonus.... Ran out of fuel. The pickup is shorter than the engine pickup and the genny will run out at 1/4 tank of fuel.
Testing flow chart. ( make one)
For this job here's how I did it.
1) Ran the genny and used my Infrared, to determine engine temp. Checked Heat exchanger, Exhaust water, and Engine block where the safety switch is located. ( Looks like a Clothes dryer safety) I got 115-126 at all points which is perfectly fine. The overheat safety generally the overheat safety will shut the engine down at 200.
2) When the engine died, I put an ohm meter across the overheat safety to make sure it wasn't weak. The circuit was completed so it wasn't that. If the Ohm meter showed an open circuit, we would have our smoking gun.
3) I put my test light on the single wire to the electric fuel pump and spun the engine. I had power.
4) So when I finally got it restarted, I had left the test light in place to test the fuel pump relay to see if it was intermittantly sticking. ( See video attached) No problem there, but when the engine started dying, the test light was strong..... and so was the exhaust... BLACK SOOT!!!! Ok now we have our diagnosis. Either trash in the fuel or a sticking needle and seat overfilling the carb. A removing of the flame arrestor ( Not reccomended for DIY) confirned, a ton of wet fuel floating out of the carb. So a simple rebuild, with a good filter system will fix this and have her purring. By the way. Most people don't know this but there is a fuel filter inside of the electric pump. If you have the cylindrical vertically mounted pump the bottom cap will twist off slightly allowing replacement of the filter.
Enjoy the video, VVVV and be safe!! Lee