Water flows through the hot spot below the air intake tunnel. No water leaks or internal corrosion needed here thank you!
Air, after being measured for volume and temperature by the air flow meter, enters the plenum through up to SIX locations. The idle air control gallery, the throttle disc(s) in the air intake tunnel(s), the extra air valve, the overrun valve, the air conditioning anti-stall valve (if fitted) and the auto transmission anti-stall valve (if fitted)
Petrol is regulated by NINE injectors, eight situated below the plenum and one connected to its rear face but not before the fuel rail and its multiple collection of pipes, hose clips and the ubiquitous fuel pressure regulator play hide and seek in its shadow.
Vacuum is felt, and used, by no less than SEVEN external functions. The overrun valve, the brake servo, the fuel pressure regulator, the automatic transmission modulator valve, the air conditioning control system, the distributor vacuum advance and the crankcase ventilation system. Each dependent upon clear suction pathways with no leaking pipes and reciprocally, the plenum itself is even more dependent upon the integrity of all the connecting components and pipe-work.
Electrical connections wander all around the plenum to SEVEN key functions fixed to its body or the adjacent inlet manifold. The throttle potentiometer, the Efi temperature sensor, the thermotime switch, the cold start injector, the main injectors below , the extra air valve and the air conditioning anti-stall valve (if fitted).
Without question, the plenum is the heart, and is at the heart, of everything that happens to the Rover SD1 Efi System. To paraphrase Trigger, the roadsweeper (with his ubiquitous broom) from ‘Only Fools and Horses’:
“Look after your Plenum and your Plenum will look after you!”
Rogue air leaks are one of the most common causes of problems encountered with the Rover SD1 Efi System. Attending to them on a routine basis will go a long way to keeping the system in good order and prevent purchase of expensive components to replace items that are not faulty.
Likewise the electrical connections are operating in the intense heat surrounding the plenum chamber and are vulnerable to connector and cable fatigue. Keeping these in good condition is key to trouble free operation of the whole system.
These are my personal observations how to care for the plenum and the standard tests required to keep it in “good heart”.
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Rover SD1 Efi Archive - The Plenum Chamber