Champion 100520 8750W Cold Start Difficulty Below 40°F

Why Your Champion 100520 8750W Won’t Start in Cold Weather

The Champion 100520 8750W Open Frame generator is a robust machine, but like all small engines, it becomes temperamental when the mercury drops. Cold-start difficulty on this model typically stems from one or more of five interconnected issues: oil that’s too thick, a choke that isn’t sealing properly, poor fuel vaporization, a weak battery (if you’re using the electric-start option), or carburetor icing when humidity is high. Understanding which one is your culprit will save you time and frustration.

At-a-Glance: Most Likely Causes

Diagnostic Walkthrough: Step-by-Step Cold-Start Troubleshooting

1. Check and change the oil if necessary.
   The most common culprit is using summer-weight oil (like SAE 30) in winter conditions. When temperatures drop below 40°F, this oil thickens dramatically, making it nearly impossible for the starter to turn the engine over. Check your current oil’s viscosity rating. If it’s SAE 30 or 10W-30, switch to a winter-appropriate grade like SAE 5W-30 or 0W-30, which flows freely in cold. Drain the old oil completely, refill with the correct grade, and try starting again. This single step resolves the majority of cold-start complaints.
2. Visually inspect the choke mechanism.
   Locate the choke lever or knob on your generator (consult your owner’s manual for the exact location on the 100520 model). Move it to the full “CHOKE” or “COLD” position and observe whether the choke plate inside the carburetor closes completely. You may need to remove the air filter cover to see it clearly. If the plate doesn’t seal fully, the engine won’t get the rich fuel mixture it needs for cold ignition. A stuck or bent choke linkage is usually the cause. Clean any debris around the linkage with a soft brush, and gently work the lever back and forth to free it up.
3. Verify fuel quality and freshness.
   Stale or low-octane fuel doesn’t vaporize well in cold. If your generator has been sitting for more than 30 days, the fuel may have degraded. Drain the old fuel from the tank and carburetor (consult your manual for the drain valve location), then refill with fresh, high-octane gasoline (87 octane minimum, 91+ preferred for cold climates). If you live in a cold region, consider using fuel with a winter-grade additive package that improves cold vaporization.
4. Test the battery voltage (electric-start models only).
   If your 100520 has an electric-start option, a weak battery is a prime suspect. Use a multimeter to measure the battery voltage. A healthy 12V battery should read 12.6V or higher at rest. If it reads below 12V, the battery is discharged and won’t provide enough cranking power in cold conditions. Recharge the battery fully using a standard 12V charger, then attempt a cold start. If the battery won’t hold a charge, it needs replacement.
5. Prime the carburetor if equipped with a primer bulb.
   Some Champion models include a manual fuel primer bulb on the carburetor. In cold weather, press this bulb 5–10 times before attempting to start. This forces fresh fuel into the carburetor bowl and helps overcome poor vaporization. If your model has a primer bulb, use it every time you start in temperatures below 40°F.
6. Check for carburetor icing by inspecting the carburetor exterior.
   In humid, cold conditions, moisture in the air can freeze inside the carburetor, blocking fuel flow. If you see frost or ice crystals on the outside of the carburetor body, or if the engine cranks but refuses to fire despite a good spark and fuel smell, carburetor icing is likely. Gently warm the carburetor with a heat gun (not a direct flame) set to low, holding it 6–8 inches away for 30–60 seconds. Never overheat the carburetor or damage the fuel lines. Once warmed, attempt a start.
7. Inspect the spark plug and ignition system.
   A weak or fouled spark plug won’t ignite a cold, lean mixture. Remove the spark plug and examine the electrode gap and condition. If the plug is black and sooty, it’s fouled—replace it. If the gap is wider than 0.030 inches, adjust or replace it. A fresh spark plug is inexpensive and often the difference between a stubborn cold start and a reliable one.
8. Perform a compression check if the engine still won’t start.
   If you’ve addressed oil viscosity, choke function, fuel quality, and battery voltage but the engine still won’t turn over, low compression may be the issue. This requires a compression tester (a tool most DIYers don’t own). If you reach this point, it’s time to call a professional technician to rule out internal engine damage.

Parts You May Need

• Winter-grade engine oil (SAE 5W-30 or 0W-30)
• Fresh gasoline (87+ octane, winter-blend preferred)
• Spark plug (Champion or equivalent, correct heat range for your model)
• 12V battery (if electric-start equipped and battery is dead)
• Carburetor rebuild kit (if icing or fuel vaporization issues persist)
• Fuel stabilizer or winter fuel additive
• Multimeter (for battery voltage testing)

When to Call a Pro

Stop troubleshooting and contact a certified small-engine technician if:

• The engine cranks normally but refuses to fire, even after you’ve confirmed spark plug, fuel, and choke are all correct.
• You suspect carburetor icing but warming doesn’t resolve the issue—the carburetor may need professional cleaning or rebuild.
• The battery is fully charged but the electric starter still won’t crank the engine; the starter motor or ignition switch may be faulty.
• You hear a grinding or unusual noise during cranking; internal engine damage may require professional diagnosis.
• You’ve completed all diagnostic steps and the problem persists; compression testing or fuel-system pressure testing may be needed.

Frequently Asked Questions

Can I use any winter oil, or does it have to match the manual?

Always follow your owner’s manual for oil viscosity. The Champion 100520 manual specifies acceptable grades for cold-weather operation. Using an oil that’s too thin can reduce engine protection; too thick and you’ll have cold-start problems. Stick to the recommended range—typically SAE 5W-30 or 0W-30 for below-40°F conditions.

How long should I let the engine warm up after a cold start?

After a successful cold start, let the engine idle for 2–3 minutes before applying load. This allows oil to circulate and the engine to reach normal operating temperature. Don’t immediately run the generator at full capacity; ease into it gradually.

Is it normal for my generator to be harder to start in cold weather?

Yes, all small engines are harder to start when cold. However, if your generator won’t start at all below 40°F despite proper maintenance, one of the five causes listed above is at play. The diagnostic steps in this article will help you identify and fix the specific issue.

Should I store my generator differently in winter?

Yes. Before winter storage, drain the fuel tank or add a fuel stabilizer to prevent vaporization issues and carburetor gum buildup. Use winter-grade oil. Store the generator in a dry location. When you’re ready to use it in spring, follow the cold-start procedure outlined above.

Disclaimer

This article provides general troubleshooting guidance for cold-start issues on small engines. Always consult your Champion 100520 8750W Open Frame owner’s manual for model-specific procedures, specifications, and safety information. If you’re uncomfortable performing any of these steps, or if the problem persists after diagnosis, contact a qualified small-engine repair technician or Champion customer support at https://www.champion.com/support/.

Source: Information adapted from official manufacturer documentation (reference). Always consult your generator owner’s manual for model-specific procedures.