The Ruston Mark 37 Injector
|A Ruston Mark 37 Injector from a VPH Engine
A Plug (overflow pipe connects here)
B Sealing washer
C Needle Valve Stop
D Injector Spring
E Spring Washer
F Spring Housing
G Nozzle Assembly
H Injector Body with inlet filter
The earliest Mark 37’s had a nozzle that was separate to the needle valve and guide and was difficult to line up correctly. Subsequent injectors, including those on Queen Anne, had a combined nozzle, needle valve and guide which is a much more satisfactory arrangement. The nozzles are machined to very high tolerances and must be kept scrupulously clean.
The injector pressure is important, and for the Mark 37 should be 3000 psi. Other makes of injector have a screw device to vary the pressure on the injector spring, but with Mark 37s shims have to be placed alongside the spring washer (E), and this involves repeated assembling, testing and dismantling until the correct pressure is reached.
|The Water-damaged Nozzle
The picture shows a nozzle that was badly pitted due to water entering the cylinders when the loco was abandoned. It is obviously a write-off. Unfortunately there seems to be no replacement nozzles to be found anywhere, in spite of contacting various specialist companies and Ruston experts.
The Wrong Nozzles
|You can see the wording FVPH on the left and FVRH on the right. Also showing the needle valve.
The engine obviously ran with VPH nozzles, and as VRH nozzles are unobtainable it was decided to use VPH nozzles in all injectors. This meant replacing the VRH nozzle and badly pitted VPH nozzle. Of course, VPH nozzles are unobtainable too, so it was decided to “borrow” nozzles (also in poor condition) from the out-of-use Ruston 0-4-0 DM shunter, which has a 6VPH engine.
|Simple Dismantling Tool
The orientation of the injector sprays is important, and an inscribed line on the nozzle must line up with a similar line on the injector body. A special tool was made to allow all the injector internals to be lined up before sliding the injector body over.
|The Assembly Jig
|Injector Internals Mounted on the Assembly Jig
The injectors were reconditioned by Rayner Diesels in Newbury. While they normally service modern diesel fuel injection equipment, they have many years expertise and still have the equipment and knowledge to service older injectors. For injectors in such a poor state, renewal of the nozzles would be the normal solution, but in the absence of spare parts the nozzles had to be brought back to life. The needles were seized in the nozzles and needed to be warmed up gently to soften the congealed diesel oil. The valve seats were badly pitted and needed carefully lapping in with very fine grinding paste. Most of the nozzle holes were blocked up.
The sealing washer (B) is a special shape as it needs to seal both the needle valve stop (C) and the injector body (H) against the full injection pressure. These washers can only be used a limited number of times, so some new ones were machined out of copper bar. Rayners were short of one good washer, so one of the injectors suffers from back-leakage until we have made and fitted a new one. This should cure the white smoke which is currently being generated by No. 1 cylinder.
If anyone knows of a source of Ruston Injector Nozzles, please let us know.