Generator brands · Engines
Yanmar Engine Repairs for Portable and Silent Diesel Generators
We repair and service Yanmar-engined generators on site across Gauteng, including the many portable diesels whose engines only look like a Yanmar. Two quite different machines carry the name: small air-cooled single-cylinder engines in open-frame portable sets, and water-cooled TNV engines in compact silent and mobile sets. Knowing which one you have comes first, because the faults, the service and the parts all differ.
Established 2006
20 years of experience
24/7 operations
We Arrive Within 1–2 Hours
(usually within 1 hour)
Free callouts and quotations
One-year warranty
Qualified and certified technicians
We Service & Repair All Generator Brands
All generator makes and models
1 kVA–20,000 kVA capability
Two engine families, two approaches
| Aspect | L series (air-cooled, one cylinder) | TNV series (water-cooled) |
|---|---|---|
| Where you find it | L series (air-cooled, one cylinder)Open-frame portable diesels | TNV series (water-cooled)Compact silent standby sets and towable site sets |
| Typical set size | L series (air-cooled, one cylinder)About 2 to 6 kVA, usually single phase | TNV series (water-cooled)From around 10 kVA into the tens of kVA, often three phase |
| Speed | L series (air-cooled, one cylinder)Usually 3,000 rpm with a two-pole alternator | TNV series (water-cooled)Usually 1,500 rpm with a four-pole alternator |
| Starting | L series (air-cooled, one cylinder)Recoil with a decompression lever; key start on many | TNV series (water-cooled)Battery and starter, often started automatically by a controller |
| Cooling | L series (air-cooled, one cylinder)Flywheel fan blowing air over a finned cylinder | TNV series (water-cooled)Radiator, coolant, water pump and thermostat |
| Fuel | L series (air-cooled, one cylinder)Small tank on the engine feeding by gravity, with a strainer and filter | TNV series (water-cooled)Water separator, fuel filter and injection pump |
| Service focus | L series (air-cooled, one cylinder)Frequent oil changes, air filter, injector, valve clearances | TNV series (water-cooled)Oil and filters, coolant, belt, water separator, battery and charger |
Identify it first
Look-alike engines and why the plate matters
Many portable generators use single-cylinder diesels built by other manufacturers to much the same layout as Yanmar’s air-cooled L series, often stamped with codes such as 178F or 186FA. Portable diesels sold under names such as Kipor and Mac Afric use air-cooled single-cylinder engines of this kind, and from the outside they can look almost identical to a Yanmar.
They are serviced in a similar way, but parts do not always swap: injectors, gaskets, filters and recoil parts differ between makers and between versions. So we read the engine plate and the block markings before ordering anything, and tell you plainly if the engine is a look-alike, because that changes the parts and sometimes whether repair is worth it.
The photo shows an open-frame portable diesel with an air-cooled single-cylinder engine of this layout. It illustrates the type of engine and is not presented as a Yanmar.
- Engine plate and block markings read first
- Parts matched to the actual engine
- Look-alikes repaired too, with honest advice on cost
Single-cylinder engines
How we work through a hard-starting portable diesel
- 01
Oil level and the low-oil switch
Many portable diesels will not start or keep running with the oil low. The level is checked with the set standing level before anything else.
- 02
Starter, battery and recoil
The engine has to turn over briskly to fire. On key-start sets a small battery that has stood for months is often the whole problem; on recoil sets, a broken rope or worn pawls.
- 03
Fuel and air
Water, sediment and stale diesel collect in the small tank on the engine, so the strainer and filter are cleaned or replaced and air bled out if the tank ran dry. A choked air filter or carboned silencer is checked at the same time.
- 04
Injector and injection pump
A carboned or dribbling injector gives a poor spray, hard starting and white smoke, so it is cleaned or replaced. The pump is checked for a sticking plunger or a worn delivery valve.
- 05
Compression and valves
The decompression lever lets the engine spin up before compression is restored. If it still will not fire, compression and valve clearances are checked: worn rings or a tight valve make starting hard.
TNV-engined silent sets
Where water-cooled Yanmar sets need attention
Water in the fuel: Fuel system repairs
The water separator ahead of the fuel filter has to be drained. Left full, it lets water reach the injection pump and injectors, which is an expensive repair.
Battery and charger: Battery not charging
A standby set starts on demand, so a tired battery or failed charger is the usual reason it does not start when the power goes.
Coolant, belt and thermostat: Overheating
A slipping belt, old coolant or a sticking thermostat shows up as high-temperature alarms on long load-shedding runs.
Oil pressure alarms: Low oil pressure
A low oil pressure shutdown can be real, or a failed switch or damaged wire. It is checked against the engine before it is trusted.
Independent service
We Service & Repair All Generator Brands
Onsite Generator Repairs is an independent generator specialist. We repair, service and maintain Yanmar equipment as part of our work on every make of generator.
Manufacturer warranty claims go through the manufacturer’s own network. If your generator is still under warranty, check the warranty terms before arranging work by anyone else.
Brand names and trademarks belong to their respective owners. Onsite Generator Repairs is an independent service and repair company.
Service areas
Where we work in Gauteng
FAQ
Frequently asked questions
My single-cylinder diesel generator is very hard to pull-start. Is that normal?
Some effort is normal, which is why there is a decompression lever. If it is much harder than usual, or will not start after a few pulls, stop: there may be a fuel, injector or compression fault, and repeated pulling only wears the recoil.
Is my generator’s engine a genuine Yanmar?
Check the maker’s name and model on the engine plate, for example an L-series or TNV model. Many similar-looking engines are made by others. We repair those too, with parts matched to the engine you actually have.
How often should the oil be changed on an air-cooled diesel?
More often than on a water-cooled engine, because the sump is small and the engine runs hot. Follow the hours in the engine manual, shorten them in dusty conditions, and check the level before every run. Our servicing and maintenance pages explain what is included.
Why do bolts and fuel lines keep coming loose on my portable diesel?
Single-cylinder engines vibrate hard, so mounting bolts, fuel lines and connections loosen or chafe over time, causing leaks and intermittent faults. They are checked and secured at every service.
Can a portable diesel run my house?
It can run essential loads, but not usually a whole house with a geyser, stove and air conditioning. The kVA sizing guide explains how to work it out. If yours struggles or will not start, see our generator repairs.
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- 24/7 operations
- We Arrive Within 1–2 Hours (usually within 1 hour)
- Free callouts and quotations