The "Morgan Owners Handbook" advises depressing the valve daily or every 200 miles, whichever comes first. The plunger should be held down for a few seconds, preferably when the engine oil is cold. The plunger is located just above the transmission tunnel on the bulkhead and is actuated by the driver's foot.
The 'one shot' lubrication valve was originally fitted to four wheel Morgans in 1950 and discontinued in 2002.The Morgan Owners Handbook warn of premature wear and a harsh ride if the 'one shot' valve is not used every 200 miles or daily. The handbook also recommends that the sliding axles and hubs are greased at 5000 mile intervals. I purchased my car in 1973 with very low mileage and a service record. I did not have a garage at the time and the car was parked on a road with a strong camber. Just a week or so after purchasing the car, I became aware of really bad brake imbalance. I discovered the front nearside brake disc had become contaminated on both sides by oil and black grease. The calliper and pads were also contaminated. A combination of the heavy road camber and the close proximity of the lower rebound spring to the brake disc appeared to be the problem, but I was surprised that the grease alone would have made such a mess. I cleaned up the rebound springs, brake discs and callipers with trichloroethylene. I then fitted new pads. Within a week the front wheels had become contaminated with oil again and I had not used the 'one shot valve' more than once. I discovered that the valve was slowly leaking oil. I removed it from the car, stripped it down and reground the mushroom valve and its seating with grinding paste. Figure 2 should hopefully show how the valve is constructed. Regrinding is straightforward. Having undone the unions and released the four oil pipes, the complete assembly can be removed from bulkhead by undoing the two bolts that secure it to the bulkhead. The mushroom valve can then be unscrewed from the plunger cap and ground in the way you would grind cylinder head valves.
On reassembly be careful to thoroughly clean all components, check the condition of the return spring and peen the threaded part of the valve to the plunger cap. Make sure the plunger cap moves freely. If the valve sticks the engine oil will flood the suspension and most probably contaminate the disc brakes too. It is surprising how quickly the oil will be evacuated from the engine. After refitting the 'one shot' valve I only reconnected the 'oil pressure pipe union' and the 'engine pipe union'(please see diagram above). Taking care to wear good safety goggles, I started the engine and observed the nearside and offside pipe union ports to check for leakage. After confirming there were no leaks I reconnected the suspension pipe unions. I have not had a problem with the valve since.
Some owners fit grease nipples on the top of the kingpins (points (C) in Figure 3) and do away with the 'one shot' system completely. The engine oil feed (point A) is then connected directly to the pressure gauge (point D). Back in the 1990's Andy Millhouse who owned the local Morgan agent "Phaeton Motors" at Emsworth, Sussex, supplied a kit to do the job. Unfortunately Phaeton has since stopped trading and Andy moved to Bristol. Living near Phaeton at the time of my rebuild, I did consider fitting the kit, but decided against it. If you look at the groove 5" from the top of the kingpin you will see just how small the oil exit holes are and they do not seem low enough to allow the grease to fill the stub axle grease reservoir. I suspect the oiler was only ever intended to provide smooth action of the top bush by preventing corrosion on the kingpin above. The lower bush is the one that wears most and fitting a gaiter around the rebound spring seems wise as it protects the lower part of the kingpin from dirt and moisture. It also helps protect the disc brake from contamination.
My personal opinion is to grease the hubs at least every 1000 miles or less and only use the 'one shot' oiler rarely. After all why dilute and contaminate good fresh grease with oil that's been circulating your engine for up to a year? If your oiler valve jams open, not only could it contaminate your disc brakes, but it could rapidly empty the oil and wreck the engine. Although Morgan fitted the valve for over 50 years they no longer fit it to their cars.
When you have finished greasing the hubs, carefully clean any excess grease from the suspension taking care not to contaminate the brake discs as they are really close to the rebound spring. Thoroughly clean your discs if you find any contamination on them. Trichloroethylene is no longer available, but there are many good specialised products available on Amazon or Halfords.Figure 3