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you have a vac. leake or the oneway check valve is not working.....
If you're talking about some electrical relay, there is none pertaining to the air brake system itself. If you're talking about the relay valve for the drive axle brakes, follow the air lines from the service side of the brake chambers up to a valve they both connect to... that's your relay valve, and you'll also see a transmission line coming from the foot valve.
the relay is in the abs pump
how do you find thepower relay valve circuit for the abs brakes
first check for battery voltage to the valve by probing the wires of the electrical connector with a volt-meter it should be about 10.5 volts if not it's probably bad.next remove the valve and check the pintle inside the valve ports for excessive carbon deposits clean the valve ports and pintle with carburetor cleaner and replace the valve if idle does not improve replace the isc valve with a new one.
electrical = broken / rubbed wire. or defective pump. plumbing = broken pipe or bad check valve. either way you are hiring a plumber to correct problem.
A dual check valve is similar to a double check valve in that it is a mechanical backflow preventer consisting of two independently acting, spring-loaded check valve.
The glowplug relay is located on the top of the engine, to the left of the fuel filter housing. It looks like a small metal box mounted on a bracket with an electrical harness attached to it. The wiring harness will have one branch come from the rear of the engine and two that seem to enter the valve covers. The glowplugs are mounted underneith the valve covers on the 1999 7.3 ltr and are energized by the relay.
It is best to replace it. The failure happens in the electrical part of the valve, not the pintle and seat.It is best to replace it. The failure happens in the electrical part of the valve, not the pintle and seat.
check fuse/relay then if not that idle air control valve 'throttle control sensor' map sensor' electronic control module' test them all.
There is no difference between check valve and NRV, both are same
faster release of service brake