A truck that isn’t moving isn’t earning. If you’re searching for a Mitsubishi 4M51 engine for sale, you probably already know that feeling. The Fighter is parked, the loads are going to someone else, and the quote to rebuild the old engine came back higher than you hoped or with a longer wait than you can afford.
We’re NJ Global Auto Parts. We supply used and rebuilt engines and ship them to fleet owners, workshops and owner drivers worldwide. The 4M51 is one of the diesel engines we handle regularly. This page covers what the engine is, its specifications, which trucks use it, the problems that finish these engines off, what we check before we sell a Mitsubishi 4M51 engine for sale, and how we get it to you. It’s written the way we’d explain it to a customer standing in the yard.
Table of Contents
What You Get With a Mitsubishi 4M51 Engine for Sale
The 4M51 is a 5.2 litre four cylinder turbo diesel from Mitsubishi’s 4M5 family. It’s a big bore, long stroke engine built for medium duty trucks. It sits alongside the smaller 4M50, which is 4.9 litres, and the two are often confused. They look alike from the outside, but they are not the same engine, and parts like pistons and liners don’t cross over.
It’s a turbocharged, intercooled direct injection engine with a cast iron block and head. Earlier versions use a conventional injection pump. Later versions moved to electronic control and common rail injection, along with emissions equipment such as EGR on some markets. What stays the same is the character: lots of torque low down, easy to work on, and very forgiving if it’s serviced on time.
That’s why a Mitsubishi 4M51 engine for sale is still easy to find a buyer for. There are a lot of Fighters out there doing honest work, and owners would much rather drop in a good engine than replace a truck that’s otherwise sound.
For background on the trucks themselves, the Mitsubishi Fuso Fighter page covers the model history, and Mitsubishi Fuso has official model information for most regions.
Mitsubishi 4M51 Engine for Sale: Full Specifications
Output varies quite a bit between the early mechanical engines and the later electronic ones, and between markets. The figures below are a guide. Your engine plate and the truck’s documents are the final word, and we match every Mitsubishi 4M51 engine for sale against them before we quote.
| Engine code | 4M51 (with suffixes by version, for example 4M51-T) |
| Layout | Inline 4 cylinder, 4 stroke diesel |
| Displacement | 5,249 cc (5.2 L) |
| Bore x stroke | 118 mm x 120 mm |
| Block and head | Cast iron |
| Aspiration | Turbocharged and intercooled |
| Injection | Direct injection. Injection pump on earlier engines, electronic common rail on later engines |
| Power | Roughly 130 to 180 kW (about 175 to 240 hp), depending on version |
| Torque | Roughly 510 to 700 Nm, depending on version |
| Fuel | Diesel. Low sulphur diesel required on common rail versions |
| Cooling | Water cooled with engine oil cooler |
| Typical use | Medium duty trucks, some buses and equipment |
If you’re not sure whether your truck has a 4M50 or a 4M51, check the engine plate or the number stamped on the block. Getting this right is the most important step in buying.
Which Trucks Use the 4M51
The 4M51 is mainly a Fuso Fighter engine. You’ll find it in:
- Mitsubishi Fuso Fighter FK and FM series medium duty trucks
- Fighter based tippers, tray trucks, curtain siders and refrigerated bodies
- Some heavier Canter and FE/FG based models in certain markets
- Some buses, fire trucks and specialist vehicles built on Fuso chassis
- Some industrial and stationary applications
Because Fighters were sold new in Japan and then exported second hand all over the world, the same truck can turn up with different engine versions depending on where it was first registered. A Japanese domestic Fighter and one sold new in Australia or Asia can have different injection systems, wiring and emissions parts. That’s why we always ask for your chassis number and a photo of your engine plate before we confirm a Mitsubishi 4M51 engine for sale will fit.
Used, Rebuilt or Long Block?
When you look at a Mitsubishi 4M51 engine for sale, you’ll usually see one of these three options.
Used complete engine. Taken from a donor truck with the turbo, injection system, manifolds and usually the starter and alternator still on. It’s the quickest and cheapest way back on the road. Good value if it has been properly tested.
Long block. Block, head, crank, pistons and the timing gear, without most of the bolt-on parts. You move your own turbo, pump or rail and injectors over. Good if your ancillaries are healthy.
Rebuilt engine. Stripped and rebuilt with new pistons or rings, liners where fitted, bearings, gaskets and seals. The head is usually reconditioned too. It costs more upfront, but for a truck that does big kilometres every week it often works out cheaper over the life of the engine.
If you’re weighing up the options, our article on buying a used diesel engine and the one on rebuilt vs used engines are worth a read.
7 Checks We Make on Every Mitsubishi 4M51 Engine for Sale
Diesel engines can look fine on a pallet and still be worn out inside. These are the seven checks we do before we’ll sell a Mitsubishi 4M51 engine for sale as a good unit.
1. Engine Number, Version and Donor Truck
We confirm the engine code and full suffix, record the engine number and note the donor truck, year and kilometres or hours where known. On this engine the version matters a lot, because it decides whether it has a pump or common rail and what wiring it needs.
2. Compression on All Four Cylinders
A diesel lives or dies on compression. We test each cylinder and look for even readings. A low cylinder usually means worn rings, a burnt valve or a head gasket problem.
3. Blow-By
We run the engine where possible and check how much blow-by comes out of the breather. Heavy blow-by and oil mist is a sign of worn rings and liners. It’s one of the most honest tests of a diesel’s real condition.
4. Head and Gasket
We look for signs of overheating, coolant in the oil, oil in the coolant and cracks around the valve seats. Overheating is what kills most 4M51 heads, usually after a radiator or fan clutch problem was ignored.
5. Injection System
On pump engines we check the pump for leaks and signs of tampering. On common rail engines we look at the injectors, the rail and the high pressure pump, and check for injector sleeve leaks. Injection problems are expensive, so you want to know about them before you pay.
6. Turbo and Oil Cooler
We check the turbo for shaft play, oil leaks and damage to the compressor wheel. We also check the oil cooler, because a leaking cooler can mix oil and coolant and look a lot like a head gasket failure.
7. What’s Included
We write down exactly what’s on the engine: turbo, pump or rail, injectors, manifolds, starter, alternator, air compressor, power steering pump and so on. That list comes with every Mitsubishi 4M51 engine for sale we quote.
Common 4M51 Problems You Should Know About
The 4M51 is a strong engine, but trucks work hard and engines wear. These are the usual problems we see, and the ones we check for on every Mitsubishi 4M51 engine for sale.
Overheating damage. Blocked radiators, failed fan clutches and low coolant lead to cracked heads and blown gaskets. Most dead 4M51 engines we see died this way.
Worn rings and liners. High kilometres, poor air filtration and dusty work sites wear the bores. The signs are blow-by, oil use and hard starting.
Injector problems. Especially on common rail versions. Poor fuel quality and water in the fuel are the usual causes. Symptoms include knocking, smoke and loss of power.
Turbo wear. Oil starvation, dirty oil and hot shutdowns wear the turbo bearings. A tired turbo means black smoke and poor pulling power.
EGR and intake build up. On later engines with EGR, soot can clog the valve and cooler. It causes poor running but it’s often fixable without changing the engine.
Does Your Truck Really Need a New Engine?
Before you buy, find out exactly what’s wrong. Some problems look like a dead engine but aren’t.
Black smoke and poor power can be a blocked air filter, a tired turbo or bad injectors. Coolant loss can be an oil cooler rather than the head gasket. Hard starting on a common rail engine can be a sensor or a fuel supply problem. A compression test and a blow-by check will tell you whether the engine itself is worn out.
If it is, a Mitsubishi 4M51 engine for sale is almost always cheaper and quicker than replacing the truck, especially if the chassis, cab and gearbox are in good order.
How to Tell a Good Mitsubishi 4M51 Engine for Sale From a Bad One
You can learn a lot from photos and a few straight questions.
Ask for a running video. A cold start and a few minutes of idle shows you how it starts, how it sounds and how much smoke it makes. A good Mitsubishi 4M51 engine for sale should start quickly and settle to a steady idle.
Look at the breather. In a running video, a light wisp from the breather is normal. Heavy smoke puffing out is not.
Look under the rocker cover. Clean, brown oil with no sludge and no milky layer is what you want.
Check the engine plate. Make sure the version matches your truck. A 4M50 sold as a 4M51 is a common mistake, and not always an honest one.
Ask about the donor. Where did the truck work, how far had it gone, and why was it parted out? A truck that was written off in an accident is a better donor than one that was parked because it wouldn’t pull.
Compare prices. If one Mitsubishi 4M51 engine for sale is far cheaper than the rest, find out why before you send money.
Pump or Common Rail: Picking the Right Version
This is where most buying mistakes happen, so it gets its own section. A 4M51 with a mechanical injection pump and a 4M51 with common rail share the same basic block and bore size, but they are run very differently.
A pump engine is controlled mostly by the pump itself and needs very little electronics. A common rail engine needs its own ECU, a wiring loom with the right plugs, a rail pressure sensor, crank and cam sensors and injectors that suit the system. Put a common rail engine into a truck built for a pump engine and you’re suddenly looking for an ECU, a loom and someone who can make them talk to the truck. It’s possible, but it’s not a weekend job.
The simple rule is to replace like with like. If your truck came with a pump engine, look for a Mitsubishi 4M51 engine for sale with a pump. If it came with common rail, stay with common rail. Some owners in markets with poor fuel quality actually prefer the older pump engines because they tolerate dirty fuel better. That’s a fair point, but it only works if your truck was built for one in the first place.
If you don’t know which you have, send us a photo of the fuel system side of your engine. We can usually tell at a glance and point you to the right Mitsubishi 4M51 engine for sale.
What Affects the Price of a Mitsubishi 4M51 Engine for Sale
- Used or rebuilt. Rebuilt costs more but comes with new internal wear parts and a longer life ahead of it.
- Version. Pump engines and common rail engines are priced differently, and demand varies by market.
- How complete it is. A complete engine with turbo, injection system and accessories costs more than a long block.
- Condition and kilometres. A low kilometre engine with good compression is worth more.
- Freight. A 4M51 is heavy. Your location and shipping method make a real difference to the delivered price.
We quote the engine, what’s included and freight together. You can see what we have on the Mitsubishi 4M51 engine product page and in our Mitsubishi engines range.
Shipping a Mitsubishi 4M51 Engine for Sale Worldwide
We ship truck engines to buyers across Africa, the Middle East, Asia, the Pacific, the Americas and Europe. Every engine is drained, sealed, strapped to a strong pallet or crated, and wrapped against water and dust.
Sea freight is the normal choice for an engine this size. It’s far cheaper than air. If your truck is off the road on a contract that can’t wait, we can price air freight too, but for most buyers sea is the sensible option.
Each Mitsubishi 4M51 engine for sale is shipped with a commercial invoice and packing list. Duties and taxes depend on your country and sometimes on whether the engine is used or rebuilt. Talk to a customs broker before it arrives. The World Customs Organization explains the general process. Our shipping policy and billing terms cover our part.
What Happens When the Engine Arrives
Before you sign for the delivery, check the crate or pallet. If it’s broken, wet or the straps have come loose, take photos while the driver is still there and write it on the delivery note. It protects you if anything was damaged on the way.
After unpacking, check the engine number matches the one on your quote and go through the list of included parts. Look closely at the injectors, the turbo inlet, the sump and any sensors, since those get knocked most in transit. If something isn’t right, send us photos straight away. We keep our own inspection photos of every Mitsubishi 4M51 engine for sale that leaves us, which makes it quick to compare and sort out.
Keep the engine covered and dry until it goes in. Leave the port covers on the turbo and intake until the last minute so nothing falls inside.
Fitting Tips From Truck Mechanics
Putting a Mitsubishi 4M51 engine for sale into a Fighter is a normal workshop job, but these steps make a big difference to how long the new engine lasts.
- Clean or replace the radiator and intercooler. Whatever cooked the old engine will cook the new one if you don’t fix it.
- Check the fan clutch and fan shroud.
- Fit new fuel filters and drain the water separator. Flush the tank if there’s any sign of water or dirt.
- Fit a new air filter and check the intake piping for splits. Dust kills diesels.
- Fresh oil, fresh filter, and prime the oil system before first start.
- Bleed the fuel system properly.
- Start it, check for leaks and let it reach full temperature before loading it up.
- Take it easy for the first few hundred kilometres and change the oil early.
Looking After the 4M51 Once It’s Working
A 4M51 that’s looked after will do a lot of work. Whether you fit a used or a rebuilt Mitsubishi 4M51 engine for sale, keep these habits:
- Change the oil and filters on time, and sooner in dusty or heavy work.
- Keep the air filter clean and the intake sealed.
- Watch the temperature gauge. Stop and check at the first sign of overheating.
- Let the turbo cool for a minute after a hard run before switching off.
- Use clean fuel and drain the water separator regularly.
- Keep an eye on oil level. A change in consumption is an early warning.
Buying for a Fleet
Many of our 4M51 customers run more than one Fighter. If you’re managing a fleet, we can hold engines, ship several together to reduce freight per unit, and keep test records for every Mitsubishi 4M51 engine for sale we send you. Some fleet owners keep a spare engine on the shelf so a breakdown costs them a day instead of a month. Tell us how many trucks you run and we’ll put a proposal together.
Questions to Ask Before You Pay for a Mitsubishi 4M51 Engine for Sale
- What is the full engine code and suffix, and does it match my truck?
- What were the compression readings on all four cylinders?
- Can I see a cold start video?
- Pump or common rail? Which injection parts are included?
- What truck did it come from, and how far had it gone?
- What warranty comes with it, and what do I need to do to keep it valid?
- How will it be packed and what will it cost to get it to me?
Other Diesel Engines We Supply
If you came for a Mitsubishi 4M51 engine for sale but run other trucks as well, we also supply:
- Mitsubishi 4D56 turbo diesel for L200, Pajero and Canter light trucks
- Mitsubishi 8DC9 V8 diesel for heavy Fuso trucks
- Isuzu 4HK1 for NPR, NQR and Forward trucks
- Cummins QSB for machines, gensets and boats
- Mercedes-Benz OM366 for medium duty trucks and buses
You’ll find the full range in our used engines section.
Why Buy From NJ Global Auto Parts
Every Mitsubishi 4M51 engine for sale we supply goes through the same checks, because we’ve seen what goes wrong in the used engine trade: wrong versions, missing parts, engines that were never started. We’d rather not be part of that. Every engine we sell is checked, photographed and described honestly, and if we don’t think it’s right for your truck, we’ll tell you.
Learn more about us, read our refund and returns policy or browse the shop. More guides are on the blog.
Frequently Asked Questions
What’s the difference between the 4M50 and the 4M51?
The 4M50 is 4.9 litres and the 4M51 is 5.2 litres, with a bigger bore. Pistons and some internal parts are different. Always check the engine plate.
Is the 4M51 a reliable engine?
Yes. Most failures come from overheating, dust or poor servicing rather than a design fault.
Will a Japanese 4M51 fit my export Fighter?
Often yes, but injection and wiring can differ between versions. Send us your chassis number and engine plate photo and we’ll check.
Is your Mitsubishi 4M51 engine for sale used or rebuilt?
We offer both. Every quote says clearly which one it is.
Does it come with a warranty?
Yes. Terms depend on whether it’s used or rebuilt and are written on your quote.
Do you ship to my country?
Very likely. We ship worldwide, mostly by sea, and quote freight before you pay.
A Mitsubishi 4M51 engine for sale is only worth buying if it’s the right version, it’s been tested, and the seller stands behind it. That’s how we work. Send us your chassis number and engine plate photo through the contact page, tell us where the truck is, and we’ll come back with what we have and a delivered price.