I'm replacing my long defunct Supplementary Air Valve. I'm having a problem understanding the 45 second timer which controls the SAV.

From what I've read, the timer has two functions, to increase the idle speed at start and also when the a/c is running. Since I took my a/c off, I'm not too concerned with that aspect of if.

Anyway, I see the timer has four wires to it, black, slate, white and pink/white. From looking at the EFI and Emissions Control schematic that is appropriate for my '87 V12, it seems that the black wire goes to ground, the slate wire applies power to the timer, and the white and pink/white wires should apply power to turn on the SAV and the Solenoid Vacuum Valve (I took my SVV off also) for 45 seconds.

My relay isn't doing this. When I apply power to the timer leads that connect to the black and slate wires, I don't get voltage out of the white and pink/white wire connectors.

I'm doing this test out of the car, which should rule out any wiring issues.

Could be I have a bad timer...could be I'm completely misinterpreted the wiring diagram.

Any thought?

Thanks,

John
1987 XJ-S V12
62,000 miles

 

To add more confusion to your problem the 45 second timer also controls a solenoid that shuts off vacuum to the vacuum advance on the distributor at start up. I also have an 87 and I am not sure exactly how the timer works. I never get high idle on a cold start up. The wiring schematic confuses me.

 

Here's how I read it:

White - 12v pos from fuel pump relay (12v pos to timer when the fuel pump relay is closed)

Slate- 12v pos from starter relay (12v pos to timer when key is in "start" position)

Black- Ground

Pink/white- to Supplementary Air Valve and Solenoid Vac Valve (and Purge valve on vin 133460 and earlier)

Since the SAV, SVV, and PV also get 12v pos from the fuel pump relay I am guessing that the pink/white wire provides a ground to those three items to operate them. When the 45-seconds has expired the pink/white wire must switch to 12v pos or neutral

Cheers
DD

 

Thanks Doug. Turns out mine is kaput...or I killed it while testing it while trying to figure out how it worked.

Just for laughs, I've attached a picture of the inside of the thing.

Interestingly, the convention for diodes is that the stripe denotes the negative terminal (cathode). This device has three diodes (you can see one in the lower left of the photo), and all three have the stripe towards the "+" stencil on the circuit board. Maybe I'll flip them around and see if it works any better.

The plastic case it's in says "Pektron" on it, so can't throw the usual arrows at Lucas in this case I guess.

Cheers,

John
1987 XJ-S V12, 63000 miles

 

Heh heh, over the years I've poured over quite a few jaguar wiring schematics. There have been a few times where I could just swear that the diagram shows a diode facing wrong way 'round.

In those cases I've always assumed there was "something" goin' on with the circuit design that I just couldn't get my head around.

Maybe not ?

Cheers
DD

 

My 45 sec timer was also dead, so my friend repaired it.
In the PDF attachment is the result, the parts are listed.
Timer works and maybe this may help others

 

That timer looks very easy to repair...

 

Yes, friend said, that longest time was ordering and identification of the parts (cca 1 day). Work about 2-3 hours including testing.

 

This is a bit old but I suppose issues on these cars are eternal. I have one of these timers and it did not seem to work in the car, and neither on the bench. Odd, because it is new, but perhaps I also ruined it the installation (the anomaly is the the installation is in an E-type that is the beneficiary of the EFI originally installed in an '88 XJS; I had the wiring wrong the first time, but it is now corrected) I have 2 questions:
1. the component listing and illustration above is very helpful, but how does one troubleshoot the device to determine which component needs replacement.
2. the 12v power for the device comes from the fuel pump relay. The relay coil is powered by the main relay but is only energized when the coil ground is supplied by the ECU. the ground is supplied for about 5 sec when the ignition is turned on, but then drops out. I thought that the ECU holds the ground open until the engine starts and is running. Is that incorrect, and it actually grounds the pump while the starter is engaged. It seems that this is the only way the 45 sec timer will work because if the pump relay is not energized, the timer won't have power to operate and the trigger signal from the start switch will not initiate a timer start.

Do I have this right?
Niles

 

Get rid of it. You don't need it. It's sole purpose is to eliminate vacuum advance so the catalysts will light off slightly faster. Just run the vacuum line from the manifold directly to the vacuum regulator, instead of having the solenoid in between. The only other thing the timer does is power the supplemental air valve for 45 secs when the vacuum advance is off so the idle speed isn't too low. Keep the supplemental air valve for the a/c idle increase if you have a/c.
Jon

 

Right, I understand. It's a vestigial component from previous work arounds by the factory.. I don't need it insofar as my installation does not use catalytic converters. However i left it in the harness and can use it if I feel the need to increase the idle at some point. I won't worry about it. The advance vacuum line already is directly on the manifold, and the AC already activates the idle bump valve thru the relay.
I mimicked the XJS EFI wiring as much as possible to make troubleshooting easy for someone familiar with the XJS system. I incorporated the oxygen sensors and the feedback inhibit circuits. I replaced the park/neutral switch with a new microswitch with an extended arm mounted under the full throttle switch that hits the other side of the throttle cam to sense idle position. It operates a delay relay so that if the engine is at idle for more than 5 seconds lambda feedback goes open circuit.
The project involved installing the EFI induction, adapting the coolant plumbing and air boxes, cutting up, shortening and re-terminating all the wiring, mounting all the relays, ECU and ballast, replacing the fuel pump (the E-type already has a return circuit for the fuel system). The satisfying part so far has been that after all of that and a year into the project, I bypassed the fuel relay to fill the circuit and check for leaks, then plugged everything in, hit the starter and it fired immediately and settled into a nice even idle. Can't get better than that. I've run it up to temperature and all is well. I've not driven it as the harness is not yet pulled thru the car. I 'm also waiting for Roger Bywater(AJ Engineering) to clear his backlog so he can reprogram the 16CU ECU for the early flat head engine. The the fun of tuning will begin. And adding a "EFI" placard to the back of the E-type.