look it up on this web site and match your year and model and engine type to the list. the site wil have the setup for you
www.oljeep.com
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Residual vacuum from vacuum reservoir.
Check the driver side of the intake for a loose vacuum line.
Chrysler transmissions do not have modulator valves.
the vacuum hose connects to the airbox
i think , look under the hood on, drvers side upper firewall,at back of engine area im pulling motor on a 90 grand wagoneer and i saw one there
most common cause, a vacuum leak.
Try checking the vacuum lines on the axle.
A vacuum line near the gas tank on a 2003 Jeep Grand Cherokee is there to keep the tank from locking up due to an air pressure imbalance. If there is an imbalance of air pressure the tank will vapor lock and the engine will not get fuel.
The engine does not produce enough vacuum to be usable.
That is the vacuum supply for the HVAC control.
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The engine is the vacuum pump. All the vacuum operated accessories are operated by the vacuum supplied from the engine.
A gasoline engine makes it's own vacuum. The diesel engine has a vacuum pump next to the power steering pump.A gasoline engine makes it's own vacuum. The diesel engine has a vacuum pump next to the power steering pump.
The engine does not produce enough vacuum to be usable
There is a very good chance this is caused by a vacuum leak somewhere. An old way to check for vacuum leaks is to take an unlit opened propane torch and wait for the engine to surge and you found your leak.