A generator that will not start, will not stay running, or trips when loads are connected is rarely dead for good. On the petrol and diesel generators we service, the same handful of parts account for almost every no-start call. Work through these in order — each check rules out the part in front of it before you move to the next.

Start Here: Symptom to Likely Part

1. Battery — The #1 Cause of "Nothing Happens"

On any electric-start generator (which is most modern petrol and diesel units), a flat or aged battery is the single most common reason the generator does nothing when you turn the key. A battery that cranked strongly last season can be too weak to turn the engine this season, especially after months of storage.

How to confirm: Turn the key. If there is a slow groan, a series of clicks, or nothing at all, check the battery voltage with a multimeter — anything below 11.5V under load (or 12.4V at rest) is too low to reliably crank.

Fix: Recharge or replace the battery. On Kenyan generators, batteries are typically KSh 4,000–12,000 depending on amp-hour rating and brand. See our car batteries range for replacements.

2. Spark Plug — Petrol Units That Won't Fire

On petrol generators, the spark plug ignites the fuel-air mixture. A fouled, worn, or incorrectly gapped spark plug causes hard starting, rough running, and generators that start then immediately die. This is the single most common reason a petrol generator that ran fine last month won't start today.

How to confirm: Remove the plug and inspect. A healthy plug is light brown/tan with clean electrodes. A fouled plug is black and sooty (running rich) or wet with fuel (flooded). Check the electrode gap against spec.

Fix: Spark plugs are KSh 350–800 and take minutes to replace — swap it before you look at anything else.

3. Fuel Filter — Surges, Stalls, Power Loss

Fuel quality in Kenya varies, and a clogged fuel filter is one of the most common reasons a generator that used to run reliably starts to surge, stalls under load, or refuses to start altogether. On petrol units, this is easy to overlook because the filter is often tucked inside the fuel line.

How to confirm: If the generator runs fine at light load but stalls when appliances are added, fuel delivery is being restricted. On diesel generators especially, a clogged filter shows up as low power output under load.

Fix: Replace the fuel filter — typically KSh 800–2,500. This is a five-minute job and one of the highest-value maintenance items on any generator.

4. Carburetor — Petrol Units Left Idle

If a petrol generator has been sitting unused for weeks or months — common between power-outage seasons or between work sites — the petrol in the carburetor evaporates and leaves behind a varnish that gums up the small jets. This shows up as a generator that won't start at all, or one that starts briefly then dies.

How to confirm: If the generator has sat idle for more than 4–6 weeks and now won't start despite a good spark plug and fresh fuel, the carburetor is the next place to look.

Fix: Carburetor clean or rebuild kit — the parts cost KSh 1,500–5,000 plus labour. Prevent this by running the generator dry before long storage, or by adding a fuel stabiliser.

5. Starter Solenoid — Single Click, No Crank

On electric-start models, the starter solenoid bridges the battery to the starter motor. When it fails, you get a single loud click when you turn the key, but nothing cranks. This is often mistaken for a flat battery, but the giveaway is that the battery is holding good voltage and the click is distinctly singular.

How to confirm: Measure battery voltage at rest. If it is over 12.4V and you get a single click with no crank, the solenoid is the most likely cause.

Fix: Starter solenoid replacement is typically KSh 2,500–8,000 plus labour.

6. AVR — Runs But Voltage is Unstable

The AVR (Automatic Voltage Regulator) keeps generator output voltage stable within a usable range. When it fails, the generator still starts and runs, but the voltage it produces may be too high, too low, or fluctuating — which trips appliances, damages sensitive electronics, or causes protective breakers to trip immediately.

How to confirm: Measure generator output with a multimeter. Anything outside 220–240V AC (for a single-phase domestic generator) or fluctuating by more than a few volts under steady load points to an AVR problem.

Fix: AVR replacement is KSh 3,500–15,000 depending on generator size. This is a common wear part on generators in regular use — not a sign the alternator has failed.

Frequently Asked Questions

What to Do Next

If you can tell us the generator make, model, and what it is doing (or not doing), we can almost always narrow down the part in question over WhatsApp — usually without a visit just to diagnose.

Browse our current backup generator range, or our genuine generator spare parts category for the model you already own.

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