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“Petrol engines have a throttle in the air flow path. When throttle is closed there is vacuum in the induction manifold. This vacuum is used to power assist the brakes.
In a diesel engines there is no throttle in the air intake path. Engine speed variation is by varying the amount of fuel injected. Hence there is no vacuum generated.
Because there is no vacuum , a separate vacuum pump is operated, this is used to power assist the brakes.”
Also, vacuum is used for the Heat/AC controls - duct door flaps.
Incorrect. That pump operates the HVAC control door. It also operates the auto locking axle hubs.
Correct on no tappable vacuum source on Diesel engines.
‘99 up use a hydraulic booster to assist the apply of piston of brake master cylinder.
Pre ‘99 used an engine driven vacuum pump to supply vacuum to a vacuum assist brake booster.
Ford Doctor was replying to you saying that the electric pump was only on trucks with ESOF and auto hubs and the thread is about the electric pump. At least I think that.
Big Horn, If you look at post #6, You will see what Ford Doctor is referring to brother🙂