Cummins A058U955 Won’t Start: Diagnostic Guide

At-a-Glance: Most Likely Causes

Diagnostic Walkthrough

Follow these steps in order. Most of these checks take just a few minutes and require only basic tools you likely have at home.

1. Check the fuel valve. Locate the fuel shut-off valve on the fuel line between the tank and carburetor. Turn it to the ON position (usually marked with an arrow or “I” symbol). This is the single most overlooked cause of no-start conditions. Try starting the engine again.
2. Verify the choke position. The choke lever or knob should be in the CLOSED position (or CHOKE ON) for a cold start. If the engine is warm, move it to OPEN (CHOKE OFF). Incorrect choke position prevents fuel from reaching the combustion chamber. Adjust and attempt to start.
3. Check the oil level. Remove the dipstick and wipe it clean. Reinsert fully, then remove again to read the level. If oil is below the MIN mark, the low-oil shutdown safety switch may be preventing ignition. Add the correct oil type and grade per your manual until the level reaches the full mark. Retry starting.
4. Inspect the spark plug. Locate the spark plug (usually a single plug on top of the engine head). Unscrew it with a spark plug socket. Look for black carbon buildup (fouling), a gap that’s too wide, or visible damage. If fouled, clean it with a wire brush or replace it. If the gap is incorrect (typically 0.025–0.030 inches for this model), adjust or replace. Reinstall and try starting.
5. Assess fuel freshness. Smell the fuel in the tank. Stale fuel (sitting more than 30 days, especially in warm climates) becomes gummy and won’t burn. If the fuel smells off or looks cloudy, drain the tank completely using a fuel siphon or by removing the drain plug. Refill with fresh, clean gasoline from a reputable source. Do not use old fuel from a jerry can that’s been sitting in a shed.
6. Check for water in the fuel. If the engine has sat in humid conditions, condensation may have accumulated in the tank. Drain the fuel tank and inspect the bottom. If you see a layer of water, drain it completely, rinse the tank if possible, and refill with fresh fuel. Water prevents combustion and can corrode internal fuel system components.
7. Inspect the carburetor for visible gum. If the engine has not run in several months, the carburetor passages may be clogged with varnish. Look for a fuel line inlet to the carburetor. If you see a small drain screw at the bottom of the carburetor bowl, open it over a container to drain old fuel. If the carburetor is heavily gummed (fuel won’t flow or flows very slowly), you may need a carburetor rebuild kit or professional cleaning.
8. Verify the ignition switch and kill switch. Make sure the ignition switch is in the ON position and any kill switch (emergency stop) is in the RUN position. Some models have a safety interlock that prevents starting if a cover or guard is not properly seated—check that all protective covers are in place and latched.

Parts You May Need

• Spark plug (correct type and heat range for your model)
• Carburetor rebuild kit
• Fuel filter
• Engine oil (correct viscosity per manual)
• Fresh gasoline (ethanol-free preferred for small engines)
• Fuel stabilizer (for long-term storage)

When to Call a Pro

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

• The engine cranks but will not fire after you’ve checked fuel, spark plug, choke, and oil level.
• The spark plug is wet with fuel but the engine still won’t start (suggests a timing or compression issue).
• The carburetor is heavily varnished and you lack experience with carburetor disassembly.
• You hear no cranking sound when you turn the ignition key or pull the starter cord (electrical or mechanical failure).
• Fuel is leaking from the carburetor, fuel line, or tank (safety hazard).
• You’ve replaced the spark plug and verified fuel delivery, but the engine still won’t start after 15 minutes of troubleshooting.

Frequently Asked Questions

Why does my engine crank but not start?

Cranking without starting usually means the engine is turning over but not igniting fuel. The most common causes are a fouled spark plug (no spark), no fuel reaching the cylinders (clogged carburetor or closed fuel valve), or incorrect choke position. Start by checking the spark plug for carbon buildup and the fuel valve for the ON position.

Can I use old fuel that’s been sitting in a can for a year?

No. Gasoline degrades over time, especially in warm or humid conditions. Fuel older than 30 days can form varnish and gum that clogs the carburetor and fuel injectors. Always use fresh fuel from a reputable gas station. For long-term storage (more than a month), add a fuel stabilizer to prevent degradation.

What does the low-oil shutdown do?

The low-oil shutdown is a safety feature that prevents the engine from running if the oil level falls below a critical threshold. This protects the engine from bearing damage and seizure. If the oil level is low, the engine will not start or will shut off immediately after starting. Check and top up the oil to the full mark on the dipstick.

How do I know if my spark plug is bad?

Remove the spark plug and inspect it. A good spark plug has a light tan or gray color on the electrode. A fouled plug will be black and sooty, wet with fuel, or have a gap that’s too wide. If the plug is fouled, clean it with a wire brush or replace it. If you’re unsure, replacement is inexpensive and often solves no-start issues.

Disclaimer

This article provides general troubleshooting guidance for small-engine no-start conditions. Always consult your Cummins A058U955 owner’s manual for model-specific procedures, maintenance intervals, oil specifications, and safety precautions. If you are not comfortable performing these checks, contact a qualified technician. Improper maintenance or repair can result in engine damage or personal injury.