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ProServiceGenerator Repairs

Combustion Faults · Gauteng

Cranks, But Won’t Start.
Fuel and Ignition First.

Cranks but will not start means the engine turns and still does not fire. That points to fuel, air in the lines, glow plugs or spark, not a starter that is failing to turn. ProService Generator Repairs proves delivery and ignition on site across Gauteng.

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  • Fuel and ignition diagnosis
  • Diesel glow plug checks
  • Petrol spark and carburettor
  • Onsite Gauteng repairs
Two technicians checking fuel delivery on a diesel generator that cranks but will not start

The Fault

What causes a generator to crank but not start?

If the starter is spinning the engine at a healthy speed and the set still will not fire, the start circuit has already done its job. The fault is now whether fuel and ignition (or compression heat on a diesel) are present at the right time. That is a different job from a generator that does not crank at all.

On diesel generators the usual path is fuel. Air in the lines after a filter change, a lift pump that cannot hold prime, water in the tank, or injectors that no longer atomise will all produce strong cranking with no combustion. Cold-start aids matter too: failed glow plugs or intake heaters leave a diesel turning over without firing, especially on standby sets that sit for days between outages.

On petrol generators the picture is spark and mixture. A fouled plug, a failed coil, a flooded carburettor or stale fuel in the bowl will crank endlessly. Recoil and electric-start petrol units show the same combustion faults once the engine is actually turning.

We diagnose this on site for homes and businesses in Johannesburg, Midrand, the East Rand and across Gauteng. The aim is to prove fuel delivery and ignition before any injector or carburettor is stripped.

Turns over, will not fire?

Call or WhatsApp 082 057 4605. We diagnose fuel and ignition on site.

Call 082 057 4605WhatsAppRequest a Quote

What You Might See

Symptoms of a crank-no-start

  • 01

    Turns over, never fires

    Steady cranking, no combustion sound, no exhaust puff. Fuel is not reaching the cylinders, or there is no spark on a petrol engine.

  • 02

    Fires once, then floods

    A brief catch then a fuel smell and wet plugs or injectors. Mixture is too rich, a needle valve is stuck, or the engine is being over-fuelled while cold.

  • 03

    White vapour, no run

    On diesels this can be unburnt fuel from poor atomisation or glow-plug failure. It is not treated the same as overheating steam from the coolant system.

  • 04

    Runs only on easy-start spray

    If aerosol starter fluid makes it fire and it dies when the spray stops, the engine can run — the standing fuel or ignition system cannot.

Typical Causes

Why it turns but never runs

  • Air in diesel lines

    Loose fittings, a dry filter bowl or a leaking return line lets the injection pump lose prime. The engine cranks with nothing to burn.

  • Contaminated or empty tank

    Standby diesel grows water and sludge. Petrol goes stale. Either way the pump is working on fuel that will not ignite cleanly.

  • Glow plugs or heaters

    A diesel that cranks freely in winter but never fires often has open glow plugs or a failed heater relay — not a dead engine.

  • Injectors and lift pump

    No spray, leaking nozzles or a lift pump that cannot feed the injection pump all look like a “won’t start” engine that is mechanically sound.

  • Spark and carburettor

    Petrol sets: no spark at the plug, a stuck float, or varnish in the jets after the unit sat through several loadshedding weeks unused.

  • Kill circuit still active

    A fuel-cut solenoid or ignition kill wire held in shutdown will crank forever. We prove the cut-off is actually releasing.

How We Diagnose

Prove fuel and spark before stripping pumps

  1. 01

    Confirm cranking quality

    We check that speed and battery voltage are high enough. Slow cranking is a start-circuit job, not a fuel job.

  2. 02

    Prove fuel at the engine

    Filters, lift pump output, air leaks and solenoid operation are tested before injectors are removed.

  3. 03

    Prove spark or glow

    Petrol: spark at the plug. Diesel: glow-plug circuit and cold-start aids. No guess-swapping of pumps.

  4. 04

    Repair and start under load

    Once it fires, we confirm it stays running and will take load — a set that only idles is not finished.

Fuel System

This fault often ends in the fuel path

Cranks-but-won’t-start is the fault where fuel-system repairs earn their keep. Replacing a starter will not help an engine that is already turning. Bleeding air, restoring lift-pump pressure, or cleaning a petrol carburettor is the work that actually produces combustion.

If your generator does not turn over at all, start with the no-start diagnosis page instead. Mixing those two paths is how batteries and starters get replaced on engines that never had a cranking problem.

  • Diesel fuel path

    Tank, filters, lift pump, injection pump, injectors

  • Petrol fuel path

    Tank, tap, filter, carburettor, spark plug

  • Bleed and prime

    Air leaks after filter changes are a frequent cause

  • Related repair

    Fuel system repairs when contamination is confirmed

Google reviews of ProService Generator Repairs

  • Google Review

    The engine was turning over vigorously but wouldn't fire. They quickly realized air was trapped in the high-pressure system, bled the injector lines expertly, and got us running immediately.

  • Google Review

    Knew exactly where the blockage was.

Common Questions

Cranks but will not start — useful answers

Why does my generator crank but not start?

The starter is working. Fuel is missing, air is in the diesel lines, glow plugs are open, petrol spark is absent, or a fuel-cut solenoid is still energised. We isolate which of those is true before recommending parts.

Can a blocked fuel filter cause cranking with no start?

Yes. A filter that still looks “wet” can still starve the pump. Standby diesels that sit between outages clog slowly; the engine turns normally until it needs a real start.

Do I need new injectors if it will not fire?

Not automatically. Injectors are tested after fuel supply and air leaks are ruled out. Fitting injectors into a contaminated system repeats the same no-start a week later.

My petrol generator smells of fuel while cranking. What now?

Stop cranking. That smell usually means a flooded carburettor or a stuck float. More starting attempts wash the cylinder and foul the plug. It needs mixture and spark diagnosis, not a stronger battery.

Can a fuel solenoid stop a diesel that is cranking?

Yes. If the solenoid is not opening, the engine turns and no fuel is delivered. That is checked with the filters and for air in the lines, before the injection pump is condemned.

Can low oil make a generator crank and then die?

Yes. Some sets crank and shut down immediately when the oil switch is open. The level may be low, or the sender may be lying. Do not keep resetting it.

Still unsure what the fault is? Call or WhatsApp 082 057 4605 for onsite diagnosis.

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Related Services

Next steps if it still will not fire

Service Areas

Onsite diagnosis across Gauteng

We attend crank-no-start faults in Johannesburg, Pretoria, Sandton, Midrand, Centurion and across the East Rand and West Rand.

What to send before we attend

ProService Generator Repairs confirms an onsite visit from these details. Send what you have. A missing model number does not stop the booking.

Location
The suburb or site, so the visit can be booked in the right area.
Make and model
The generator brand and model, if they are known.
kVA
The size printed on the data plate.
Fuel type
Diesel, petrol, LPG, natural gas, or dual-fuel.
Controller model
The module name on the panel, when it is visible.
Fault or alarm
What the set does, and any text on the screen.
Photos
The generator, the data plate, and the controller or alarm. Send these on WhatsApp.

Book a Diagnosis

Engine turning, still dead?

Note whether it smells of fuel, smokes, or stays completely dry while cranking. That detail speeds up onsite diagnosis.

Include what you have. Photos of the generator and the data plate can be sent on WhatsApp.

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