Essay : Cummins in the UK – Darlington celebrates 50 years

Despite all the historical trauma of Leyland, our sole remaining builder of trucks is in American ownership but still producing plenty of vehicles for the home market and for export at the factory in Leyland, Lancashire. Its major component supplier is Cummins, which is also US owned. Now in its fiftieth year in the UK, Cummins’ current engine facility in Darlington is getting into gear for a celebration this summer and looking forward to even more production, while at the same time enjoying a link with British bus and truck building that goes back five decades.

Mike Humble has been for a look around and spoken to a few informed people about their progress and experience…


Cummins Darlington is one of two manufacturing sites they operate in the UK. Situated on the far eastern side of the town itself synonymous with engineering, the Yarm Road plant celebrates it 50th birthday.
Cummins operate two engine manufacturing sites in the UK. Situated on the far eastern side of a town itself synonymous with engineering excellence, the Darlington plant celebrates 50 years of production in 2015.

Over the past few decades, the UK-based truck and bus industry has swallowed more than its fair share of bitter pills. One by one, many of the once great and mighty truck and bus names have faded away into the ranks of memory, nostalgia or simply been forgotten. What many people fail to consider is the knock-on effect to the supply chain as the vehicle manufacturers disappear into oblivion. Some component suppliers were almost as well regarded as the manufacturer whose major parts were quite often the heart of the final product.

The key component of any motor vehicle is the powerunit and, in so far as commercials and PSV chassis are concerned, the UK was once home to some engine makers of global repute. Great names such as Gardner and Rolls-Royce powered many vehicles from the stables of AEC, ERF, Foden and Scammell – all of the aforementioned have either been lost through acquisition or through the decline of our manufacturing industry over recent decades. Those engine builders who still have a UK presence such as Perkins and CAT have since retrenched from automotive applications to concentrate solely on the less glamorous construction or power generation sectors.

The good news is we still have a major truck builder (DAF) and a collection of bus manufacturers in Britain along with their supplier of engines. American-owned Cummins have enjoyed a solid UK presence since 1956 when the company opened its first engine plant in Shotts, Lanarkshire to service a nearby construction equipment plant with powerunits and other engines for various rail-based projects. To this day, Cummins UK still remains heavily involved with rail and locomotive power through its Daventry facility – if you ever wondered where that thrum and power comes from when travelling in a Virgin Voyager train… You have Cummins to thank for that!

Early Darlington days: Cummins V8/504 blocks on the assembly line circa 1971 - Image: Chuck Rutland
Early Darlington days: Cummins V8/504 blocks on the assembly line circa 1971  Image: Chuck Rutland

The Higgs and Hill-constructed Darlington facility came online in 1965 through a joint venture with Chrysler and this year celebrates its 50th Anniversary of engine production in a town that is synonymous with engineering excellence. Cummins’ first foray into the bus market came with its V6 engine being fitted to a Daimler chassis. In fact, Darlington Corporation Transport – barely a mile from the factory – bought a batch of twelve Roadliner buses in 1967. Its earliest automotive products were no match for the likes of Gardner or Rolls-Royce for reliability or reputation, but it listened to operators and engineers views and concerns very carefully. Cummins went on to dissolve the Chrysler tie-in and tackled its early reliability issues head on with development engineers on both sides of the Atlantic turning the fortunes round to where they are today – the world’s largest and most respected, independently owned engine manufacturer.

But it hasn’t all been sweetness and light over the years at Darlington. The slump in vehicle sales around 1980 caused by a general recession forced Cummins to scale back production and cut costs. The component plant, operating next door to the assembly lines, provided parts, castings and other raw components was sadly closed down as was the production site at Shotts in Scotland and the threat of total shut-down was imminent. During this difficult period workers, plant managers, Darlington townsfolk and local politicians rallied round to make their case to the Cummins hierarchy. Without a new product in the pipeline or a huge upturn in business, Darlington seemed doomed.

The mid '80s brought the real threat of closure to Cummins Darlington.Local MP Ossie O' Brien addresses a gathering to discuss their action plan. A couple of other local Members of Parliament who went on to bigger things can be seen on the back row
The mid ’80s brought the real threat of total closure to Cummins Darlington. Local MP Ossie O’ Brien addresses a gathering to discuss their action plan. A couple of other local Members of Parliament who went on to bigger things can be seen on the back row – Tony Blair and 5th one along is the current Defence Secretary Michael Fallon MP – IMG: The Northern Echo

Cummins switch to Plan B

The plant produced components and V engines for export but when this ceased there was little to keep Darlington viable hence the total shut down plan – but the plant pulled through. In 1986, with an upgrade which cost of over £13.5 million, Cummins re-fitted the Darlington plant for production of the all new multi-purpose B Series engine in both 3.9 and 5.9-litre capacities. The larger 5.9 litre unit became the sole power unit for the revised Leyland Roadrunner – the engines first major recipient, with rival manufacturers such as Dennis, ERF and Foden eventually taking the B Series unit for their bus and truck ranges after the engine very quickly gained a superb reputation for economy, reliability and ease of servicing. This engine is still in production, albeit in a non-automotive format, to this day and has become the world’s most produced light commercial diesel power unit since its initial launch.

Leyland was starting a process of running down its own engine production and realised that, to make a global success with its vehicles, it needed to out source its power units. The well-received Roadrunner of 1984 may have looked new inside and out, but the engine was an ageing design called the 6.98 series. Despite a recent improvement programme, the 6.98 was at the end of its design scope. Leyland had decided they were to design and build no more new designs for future requirements and, besides, their reputation for engines was only, at best, tolerable. Cummins had been supplying Leyland with heavy truck engines for some years, but a new venture was being put together to bring a whole new dimension to customer/supplier collaboration.

The 5.9-litre Cummins B Series was and still is assembled at Darlington Image: Naomi Buckland / Cummins UK
The 5.9-litre Cummins B Series was and still is assembled at Darlington – Image: Naomi Buckland/Cummins UK

An engineering alliance team between Columbus USA, Darlington and Leyland was formed to develop the Cummins B Series unit into a perfectly-honed installation for its first UK recipient – the Roadrunner. Some strict design criteria ensured that items such as the alternator compressor, fuel pump, manifolding and ancillary components were fitted in ideal places to match the chassis of the truck and contribute towards reduced downtime. This was more than just a bought-in engine, it was a fully-developed package tailor-made for the Roadrunner that had more testing and development work bestowed upon it than any other truck engine at that time. Cummins’ own testing alone amounted to some 170.000 hours and nearly 12.5 million miles. The Cummins – Leyland alliance was hugely successful and continues this day with DAF.

Engines which were produced to Leyland Trucks’ specification were submitted to three phases of further testing that included 1500 hours running at full power with periods of shut down, 2500 hours at rated engine torque and a gruelling 3500 hours of 5 per cent overfuel and 10 per cent over-speed over a cycle of maximum speed, idling, maximum speed and shutdown. Development drivers also tested a prototype chassis by downshifting the gearbox almost 10,000 times to simulate a 50 per cent over-speed of almost 4200rpm, the Cummins B Series even shrugged this manoeuvre off. Key to this new engine’s inherent strength were massive bearing surfaces, a rigid cylinder block, effective cylinder head clamping and state-of-the art production facilities with all parties being focussed on a right first time approach to engine building. At the point of launch, this all-new design was by far the most tested and proven diesel engine in the world.

6 Cylinders  5.9 litres… two wheels!

Needless to say, the B Series became an instant hit with drivers, operators, fitters and the motoring press who applauded its modernity, its frugality, its reliability and low cost of ownership. And yet the B Series was an seemingly unexotic design brief that featured a simple bored block construction rather than using cylinder liners and it was not even originally designed to be reconditioned when a unit finally became life-expired. The engine not only breathed new life into existing truck designs, it soon became a popular choice of which to re-power older vehicles. Bedford buses and coaches were still popular with low-cost operators and a fully-backed conversion called Bedford Re-Power found the Cummins B Series even more customers.


I couldn’t believe just how car-like the little Roadrunner felt with its pin sharp, rock steady handling and instant performance” – Stunt and Precision driver Russell Swift on his Cummins-powered Roadrunner experience

It seems no matter who you speak to about the B Series, irrespective of their experience or exposure, the engine comes in for high praise. Even the odd celebrity has had some kind of experience with the engine. Many of you will have heard of Russell Swift – the well-known stunt driver who became a household name thanks to the famous Austin Montego TV advert. Russ had done a similar twowheel driving publicity stunt for the newly formed AWD Trucks business but not without incredible stress. He told me; ‘The handling and performance of the AWD TL was so worrying and unpredictable that the whole experience actually gave me an ulcer with stress trying to get the trick right… which I did but I vowed never to do it again in a truck.”

So when Ever-Ready contacted him to do some publicity stunt work in a Leyland Roadrunner, he rather swiftly (no pun intended) declined the offer. However, they were persistent and Russ eventually agreed to test drive the truck before committing fully. Russell told me recently: ‘I couldn’t believe just how car-like the little Roadrunner felt with its pin sharp, rock steady handling and instant performance, it was in a different league to my last lorry experience and the job went without a hitch… a lovely truck and engine” – the latter being a good testament for the Darlington built 5.9 litre Cummins B. Just like the engine in the truck in question and, indeed, myself, Russ is a Darlingtonian born and bred. When I asked him if he knew the engines’ locality, he smiled, shrugged and quipped; “well there you go you see” – nice one Russ!

Russ practicing a similar manoeuvre to the Montego - only this time using a Cummins-powered Leyland truck
Russell Swift practicing a similar manoeuvre to the Montego at Croft Circuit for a publicity display – only this time using a Cummins-powered Leyland truck. Russ told me that he thought the Roadrunner was almost “car-like” in terms of handling and performance – Image: Russell Swift Limited

I recently visited the Darlington plant to witness the current Euro 6 range of engines being produced – my first time there since 1987 as a schoolboy. For someone like me who fully understands modern technology in an engine, I still walked away breathless with admiration at the rapid advance of quality and technology for the diesel engine. It was not that long ago that a diesel engine didn’t even require an electric current to run, yet they now harness more technology and development than your average petrol car and it’s us Brits who lead the field in diesel engine emission technology – I’m quite proud of that. But Darlington also plays a massive role in green engines, its home to Cummins Emissions Solutions who develop, test and manufacture a range of emission filtration / after-treatment and exhaust catalyst systems in a very clean laboratory type environment.

Over 1.5 million engines have been produced so far and well over 100.000 emission systems on top of that, which is an impressive figure. Its latest engines are just as popular world-wide. Yet Darlington still produces the B Series along with the 8.3 litre C Series units in diesel and gas format for marine and power generation purposes only. The present range of engines for automotive use are the four and six cylinder 4.5/6.7 litre ISB and 8.9 litre ISL engines with the first two letters standing for Interact System which is Cummins’ patented electronic fuelling and telematics control programme. The bulk of Darlington’s output is destined for automotive-based applications, others are destined for power generation, plant and marine use.

An ISB engine is de-masked after painting and then it's off to join the other 1.5 million engines produced at Darlington
An ISB engine is de-masked after painting and then it’s off to join the other 1.5 million engines produced at Darlington

Despite what pundits may have you believe, we are producing more cars, vans, trucks and engines in the UK than we have done in long while. Cummins, quite rightly, recognise that Darlington is a centre of excellence within engine manufacturing thanks not only to the quality of the engines but the key attribute of the finished product – the staff who work there. The Yarm Road premises, which are situated on the extreme east side of the town that’s steeped in engineering history, currently employ over 600 people involved with the manufacture of engines to over 2000 differing customer specifications.

There is a nice relaxed atmosphere as you meander amongst the men and machines inside the factory and the feeling of camaraderie in the huge works canteen during the lunch break was more than obvious. But what did impress me the most was the attention to detail and cleanliness everywhere you look, I had a good look at a finished unit awaiting its next move to the paint booth. Not a single burr or ragged edged casting could be spotted and the factory is very highly mechanised, too. But it takes a human touch to have that all important eye for quality… and it’s certainly noticeable, too.

Cummins are at the forefront of modern technology. This Wright NBFL seen here being put through its paces on a proving track, is a full hybrid and features a 4.5 litre Cummins ISB tucked away behind the rear staircase - Image: TFL
Cummins are at the forefront of modern technology. This Wright NBFL seen here being put through its paces on a proving track, is a full hybrid and features a 4.5 litre Cummins ISB tucked away behind the rear staircase – Image: TFL


The Bus Operator Experience

But how do the Darlington built-engines perform out in the field and, more importantly, a few miles down the road? I took time out to visit a good friend and customer of mine Austin Blackburn, owner of Go-Coach Hire in Sevenoaks, to ask his frank and honest opinion. As friendly as they come but brutally honest as they go, Austin is a big fan of Cummins engines with the bulk of his service bus fleet being powered by Cummins units from the four cylinder iSB up to the legendary L10 unit. Even his brace of heritage AEC Routemasters have been re-powered with a turbocharged B and a de-rated 8.3 litre C Series.


They’ve been invaluable and I can probably say that we couldn’t and possibly, dare I say, wouldn’t have built the business to the effect that we have today without hard-grafting buses with dependable power units” – Go-Coach Hire Owner and Mechanic Austin Blackburn on the importance of a good engine

Owner Austin was keen to point out how dependable and reliable a Cummins engine is: ‘I’ve been working on these engines since 1988 and have found the B Series, especially in Euro 2 format, unbeatable. The back up is best in the business and they tend to be bulletproof. In good order, they run smoothly, efficiently and just seemingly run forever… they just get on with the job.” I asked him whether they had been that much of an asset to his business. ‘Most certainly.” He expands with: ‘They’ve been invaluable and I can probably say that we couldn’t and possibly, dare I say, wouldn’t have built the business to the effect that we have today without hard grafting buses with dependable power units.”

Not only does he run a bus and coach operation, Austin is also a time served fitter who did his apprenticeship with London Transport. His other company, The Bus Doctor, specialises in third party maintenance and repairs for PSV and light commercials. They have extensive experience with current Cummins engines, too. Austin was keen to point out that even though the current Euro 6 criteria has given many engine builders and operators something of a headache. He stated: ‘I doubt any other manufacturer has invested so much time and money into engine emissions” – he could be right.

Calling on many years of experience, Cummins have certainly helped the UK bus industry succeed to the point where they have today. The Transport De-regulation Act which came into effect in 1986 caused a great deal of heartache and uncertainty for operators and chassis builders. But it opened up the marketplace towards smaller buses rather than lumbering double deckers and Dennis were keen to exploit the new trend of Midi-buses. Subsequent models such as the Dart and Enviro 2/3/400 range all rely on Darlington built Cummins power units, Optare and Wrightbus soon developed their own range of smaller mini and midi-buses mostly powered by Darlington built engines. Even the Borris-Bus hybrid is Cummins powered.

The latest range of Euro 5 and 6 power units for Leyland-assembled DAF products are the ISB and ISL units. Four cylinder Cummins E6 engines are currently assembled in China, but not for much longer. Quality and lead time issues mean that Darlington will be taking over production later this year Image: PACCAR / Leyland Trucks LTD
DAF Trucks who also build in the UK are Cummins biggest customer. This is the new 7.5 tonne LF model which is engineered and assembled at Leyland. Image: PACCAR / Leyland Trucks LTD

Bringing it all back home – can you help?

As with many other global companies, Cummins have plants overseas to supply local markets or to make a product cost efficient. The current Euro 6 four cylinder ISB engine is produced in China but all that is to change in the not-too-distant future. In the quest of better lead times mainly to cater for the thriving local UK bus manufacturing industry, Cummins have decided to bring production of this unit into to Darlington which takes effect as of later this year. The news is a great morale booster and testimony to how well regarded the County Durham facility is both within the company itself and is reckoned to boost annual production to the tune of an extra 1000 units annually.

Worthy of celebration indeed but Cummins also have that covered – to commemorate 50 years of the factory, the company is holding an event on 11 July at the Darlington site. They are keen to source the oldest Cummins-powered vehicles still on the road to join their display of vehicles. If you own or know anyone who runs a heritage Cummins-powered bus or truck who may like to join in the event, contact Steve Nendick on 01325 556717 or send an email to: for further information.

To conclude, it’s fair to say that Cummins in the UK has an illustrious past, a respected present and a bright future in engine manufacturing – and long may it continue.

Happy 50th Cummins Darlington!

[Editor’s Note: Thanks are due to Mike Brown, Tim Hamilton and the good folk at the Darlington plant for their great hospitality on the day. Also to Russell Swift and Austin Blackburn for the thoughts and experiences they have shared.]


Mike Humble


  1. Great article Mike. It reminds us of how valuable Cummins are to the North East economy as well as Nissan etc. They don’t get the same amount of recognition, although the local BBC have done TV business reports about them.

    In January 1986 I was working on a filming job at the Darlington factory (same day as the Shuttle Challenger blew up). That’s how I remember where I was back then.

  2. Great article, and good news that the 4 cylinder ISB is coming back onshore. It’s also worth noting that the UK is heavily involved in the development of these engines as well. A Cummins powered DAF LF is a lot more British than the layman might think!

    The rise of Dennis is worth noting, as the Cummins powered Dennis Dart in many ways is THE British bus of the last 20 years, and virtually all Dennis and ADL buses have been Cummins powered for 25 years now.

  3. “What people many fail to consider is the knock-on effect to the supply chain as the vehicle manufacturers disappear into oblivion. Some component suppliers were almost as well regarded as the manufacturer whose major parts were quite often the heart of the final product.”

    This is a very good point and something which makes me very angry at clueless London politicians, civil servants and the experts who advise them. Everytime they fail to support British industry, isn’t just one company they destroy, but an entire supply chain.

    Once that supply chain is gone, it is very hard to rebuild. Our motor industry has recovered to a degree from the depths it fell to durring the late 70’s and early 80’s. However alot of components are imported, manufacturers have wanted to increase local content, but have found the suppliers no longer exist.

    The loss of that supply chain, means the loss of potential export orders and other sales. That is why the London elite are crazy to let our industrial champions fail, those companies supported an ecosystem of small and medium firms.

  4. It’s time the less glamorous parts of the motor industry like Cummins and Dennis are given more recognition. Cummins now looks set to last a very long time in Darlington and like Nissan in Sunderland, they are prospering due to making a competitive, reliable product people want to buy.

  5. A conventional historical review, good reading, but lacking many vital details. The trauma of stagnation of Leyland Truck and Bus happened because most of the Commonwealth nations abolished trade protection of Commonwealth Preference from 1965, and engineering industries in the UK had to sell volume on the continent of Europe to survive. The distribution networks were in place although not complete, with the British flag everywhere, but from 1898 all mainland industries had done away with inches. For participation in the Common Market, the UK had to convert the factories to metric standards, or Europe would not buy volume.

    This began with the Leyland National Bus, but conversion was sabotaged by politicians. The crashing of industry from the early Eighties occurred because new customers for the LNB, Marathon and all flagbearer vehicles shown at the 1973 Brussels Show were found to be non-metric, and all customers who bought them stopped purchasing from Britain. This made the factories stall from lack of orders.

    The Cummins short-stroke V-diesels were a commercial disaster, with high noise, unequal firing intervals in the V-6s and unrealiability. The sound of a Dodge six-wheeler with the VAL V-6 was no less than horrible. Cummins lost all profit from their V diesels in guarantee claims and had to close many of their offices around Europe, which I learned from an escapee from Cummins Sweden who went to Scammell. The Perkins V-8 was also designed following American practice, and one hundred engines for Lyon in France were installed in Berliet PR100A buses costing £5 million. They were a nightmare because of the Anglo-American Unified inch threads, bearing sizes and other inch-derived features.

    The Leyland National Bus was even worse at St Etienne, and I found the Daimler Roadliner on a visit to Calgary (Canada) after leaving BLMC in April 1972. The Krupp truck range of the Sixties was powered by a licence-built C-Motor (Cummins VINE) and was unacceptable, so their truck production was closed down. The same thing happened with the Ford Cargo/Cummins L10 and the Ford Transcontinental with the NT335. The key to this was establishment of subsidiaries of Cross International of Detroit in Japan, Stuttgart and Liverpool to supply machine tools to the auto factories. They would only cut Unified thread pitches, and the same problem afflicted the car industry as much as the CV sector.

    • This is a very strange viewpoint. Why are Unified threads “a disaster ” ? They may require different tools, and the thread angles may be slightly different from metric threads, but there are many problems in metric threads as well, with metric coarse and metric fine having very different properties. Furthermore, whilst there are those ( such as Mike ) who are obsessed with SI units , the plain fact is that the largest engineering manufacturing nation in the world ( the USA ) has always used non-metric measures . The troubles in my view lay elsewhere , with lack of development expenditure, strikes etc being at the forefornt

  6. Interesting comment Mike, but I fear there was a whole lot more to the implosion of Leyland Bus & Truck… much much more than metrification and the likes.

    Duplicated product ranges – AEC Leyland Bristol Daimler Scammell Albion. Untried technology going out of the door despite pleas from engineers – Gas turbine 500 & AEC V8 engines. The syphoning off of £millions from the truck and bus profits to prop up badly run car and component plants. Leyland’s Management attitude of “take it or leave it” towards their customers. Forcing the end user to unwittingly complete the development work for them – Leyland National / Railcars / Royal Tiger Doyen / Daimler DMS. Or how about allowing their customers (LT & WMPTE) to cancel hundreds of buses owing to dithering and production location issues delaying delivery times in some cases by years – Leyland Titan.

    And simply put in layman’s terms… better and more dependable bus & truck products from overseas rivals. Need more be said?

    The article serves the purpose to raise a glass to world class engineers and products that we still make right here rather than bemoan the passing of what was otherwise… inevitable looking back.

    I mentioned that Cummins early dabbles into the PSV & HGV markets were fairly poor, but as you stated, they stood on their warranties. Unlike Leyland Motors in the early ’70s, they learned their lessons quickly and got on with improving, developing and FIGHTING back for customer respect. Everyone makes a boob now and again, but it takes a little extra effort and some determination to learn from the mistakes. By the time Leyland buck and truss got on some form of even keel with products like T45 and a slimmed down bus portfolio, the likes of DAF / MB / Scania and Volvo set up their stalls, plugged in their vacuum cleaners and sucked the major custom up.

    Not just that, but other British companies like MCW and Dennis in the bus world hustled their way into otherwise pi**ed off Leyland customers and gave them what they REALLY wanted – no frills basic and dependable engineering… delivered on-time.

    • Yes, when you look at something like a Dennis Dart, there’s nothing radical about it, but it’s bringing together decent components and providing exactly what the market wanted. 11,000 produced in 18 years! To give an indication of its success, 7,000 of the ubiquitous Leyland Nationals were produced…

  7. As an Engineer myself, I find this story utterly heart warming, especially the part about bringing engine manufacture back to the UK from China.

    What I’d like to see now is more companies purchasing the Leyland Trucks “DAF” badged products. I live close to a large Royal Mail distribution depot and have noticed recently that among the DAFs, I’m seeing MANs starting to appear. What’s all that about?


  8. I have lived in Darlington for 25 years. I am obviously aware of the Cummins factory but not that it was at the fore front of technology and so well respected. Thanks for enlightening me.

  9. An enlightening article.
    I can’t find any news why MANs are appearing at Royal Mail depots. Perhaps they were able to make a better deal? Perhaps DAF’s marketing could still be improved, even if they already have the largest share of the UK market. Would having Leyland Trucks products available badged as “Leyland” in parallel with “DAF” make the slightest difference?

  10. Hi,
    Great article

    In 1965 was employed in the Tool Room at the Glass building next door to the engine plant on Yarm Road when the building was still being completed – we had our lunches in the contractors hut at the front of the building until the building was finally completed and the canteen opened. Many stories about this time in our lives!

    We wondered if there are any of the original staff still around if so we would like to hear from them – we know one former Engine Plant employee who followed us out to New Zealand – we came here in December 1969.

    At the large “on the water boat show” here in Auckland in 2014 we visited the Cummins stand and met one of the representatives and this resulted in a Cummins black mat and a 2015 diary being given to us and we now receive the newsletters.

    Great stuff, well done.


  11. Cummins was a company that lead the way, I joined Cummins as a 22 year old, possible end 62 early 63, I was number eight on the payroll and the first draughtsman at the site, whilst still in the Mud huts, I even remember the huge fuel tanks pop out of the ground in front of the component plant like a submarines coming to the surface.
    One thing I liked about the Cummins policy was how the American boss was happy to sit in the works canteen with all the plebs including me, that was an eye opener as down in Coventry where I did my apprenticeship, we had five canteens, one for each grade of employee, I did not stay long as I left to set up my own engineering company as precision engineering was in its infancy and Darlington was a forerunner in bring new industry to the North East, I doubt if there will be many of the old school still around as I in my 75th year.Would be interested to hear from Ron

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