OFF THE GROUND
ONCE you’ve ascertained that the lift is going as planned, reach back into the 4x4 and re-start the engine. The jack will begin taking the weight of the 4x4, so it will require careful monitoring. Most exhaust jacks can lift around two tonnes but shouldn’t be filled with more than 10psi, so if the bag stops lifting the 4x4 or appears fully inflated, cut the engine again. The one-way valve in the hose will keep the bag inflated even with the engine off.