David Ralph (TTT2 24 – June 2014) described his solution to fitting a low oil pressure warning system to his MPJG engine. I have had similar concerns recently and decided to come up with a system fitted directly to the engine and with an audible as well as visual warning.
The threads on the block for brass unions (line to oil pressure gauge, block and cylinder head oil line and the block tap) are 1/8BSP-28. This turns out to be a standard thread used in pneumatic equipment, so a range of fittings is readily available. To clear the oil pump I used a 40mm extension piece, then a Y-connector. One port was used for a low oil pressure switch (3-6 psi) and the other for the relocated oil gauge union. Electrical supply was taken from my auxiliary fuse box under the dash, to a combined buzzer/red lamp (eBay, from Hong Kong) then to the oil switch. Earth is via the oil switch. Photo 1 shows the arrangement.
Photo 1 – Low oil Pressure Switch installed
All parts (Photo 2) were sourced via eBay, costing under £20, including the Dowty washers which are much better than fibre washers. In the event I did not use the plastic switch panel as too modern and instead made a matching panel to the additional under dash switch panel. Please note the 16mm dimension in the photo for the hole should be 20mm.
Photo 2 – Low Oil Pressure Switch components
Now I only have to concentrate on the speedometer and the water temperature when driving.