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While tracing the wiring for my injectors today, I notices the vacuum valve/switch to the fuel pressure regulator.
The vacuum line on the top of the switch runs to the FPR on the front of the A fuel rail.
there is no vacuum line to the connector on the bottom of the valve. Is this right?
the car has been in a shop where they did an alternator swap, and the mechanic was playing around with this part of the underhood area. He pulled off the air cleaner.
Where should the vacuum from the swich to the FPR be fed from?
On a USA car that would be a dump valve for the cruise control. Not sure about other markets...but I've never heard of it being tied-in with the pressure regulators.
Worthy of some research, but I think something is amiss.
Scott
The FPRs have a short vac tube coming out of their front face going to a spigot on the end if the inlet manifold.
In your photo, as Doug said, that blue item is part of the cruise control vacuum activation system. If you follow that tube coming out if the top of it, you should (might!) find it leads to the vac solenoids at the back of the cruise control bellows.
Some models had a vacuum switch mounted on the fuel rail, LH side, which sensed fuel temperature. The vacuum hose went from the supply spigot to the switch and then from the switch to the fuel pressure regulator. At xxx-temperature the switch opened to dump vacuum, thus increasing fuel pressure.
It should be a "safety switch" for cruise control. As wrote Doug, it is on the tubing between the vacuum port and cruise control. My H&E this have and Jaguar made this step after some accidents, when cruise control worked after switching "OFF". I think.
Last edited by roman_mg; Oct 21, 2019 at 07:08 AM.
Doug nailed it. It is definitely connected to the FPR. I traced the wiring to a sensor on the LH fuel rail.
looks like it is intended as an enrichment switch. That means the vacuum source is coming from the RH manifold.
I also found this in the archives
So it looks like the blue valve in my first pic is the vacuum delay valve. And it definitely controls the vacuum to the FPR. Since everything Ive seen so far says the vacuum for the charcoal canister setup is sourced from the LH manifold, I am betting the FPR vacuum source is the RH manifold.
My next task is to find where the 45 second timer module is.
Looks like its time to replace a lot of the vacuum tubing, and bring it up where it can be seen. Its all tucked under the manifold now. Im sure I will find a tee somewhere with an empty connection.
I love how consistent these cars are!
But now I am going to trace the vacuum cruise control
If I get the car dialed it, I am hoping for a break in the weather to drive it to its new home on the Olympic Peninsula in Wa
Last edited by scottpeterd; Oct 21, 2019 at 07:58 AM.
The temperature switch is on LH water manifold, not the fuel rail. Continuity check shows that it is connected to the blue solenoid valve controlling the FPR
Vacuum switch for the FPR
