The Córas Iompair Éireann611 classlocomotives were delivered from the manufacturers, Motorenfabrik Deutz at Cologne, Germany. They were delivered between December 1961 and February 1962, entering revenue earning service in the following August after receiving the new tan / black paint job at Inchicore.
Nos. 611 to 617 were a larger development of the earlier 601 class locomotives. They were fitted with a Deutz F/A8L 714 engine of 120 kilowatts (160 hp), with Voith hydraulic transmission, weighed 22 tonnes (22 long tons; 24 short tons) and had a maximum speed of 42 kilometres per hour (26 mph).
They went into traffic in various parts of the country, as shunting engines at smaller depots such as Dublin's North City Mills siding, and branch line duties such as the Loughrea branch line between Attymon and Loughrea. They briefly appeared on the Limerick - Foynes mixed train service for a few months until that line was closed in 1963. Unlike the earlier 601 class, these locomotives were fitted with brake connections enabling them to work passenger trains. Apart from their journeys on the Foynes and Loughrea lines, they never hauled passengers anywhere else until preservation in Downpatrick, where all three preserved have served on public passenger trains.
With their original lightweight branch line haunts all closed, and therefore little to do, they were withdrawn from service between 1967 and 1977. Nos. 611, 613, 615, 616 and 617 were sold to Cómhlucht Siúicre Éireann (Irish Sugar Co., now known as Greencore) in 1977. Four of these locomotives have been preserved, with the remaining three scrapped.
