XJ6 & XJ12 Series I, II & III 1968-1992

84 XJ6 electrical question

Old 12-09-2011, 03:00 PM
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Default 84 XJ6 electrical question

Jaguar electrical wiring question: 1984 XJ6 EFI 4.2L (California Car): Previous owner rewired "Air Injection Switching Valve". I am looking at wiring diagram for the valve and it shows a Resistor and a Diode across the leads to the valve; the resistor and diode are missing, does any one know the values of these parts or part numbers? What would (failure/effect) if the resistor and diode were not in place for a long period of time? Thanks David
Old 12-15-2011, 12:52 PM
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Default Wiring diagram

Attached is the wiring diagram with the diode/resistor circuit.
Attached Thumbnails 84 XJ6 electrical question-xj6-efi-diagram.png.jpg  
Old 12-15-2011, 01:49 PM
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FWIW I don't the know the values of the resistor or diode...nor do I know what the long term failure would be if they weren't there.

As you probably already know from reviewing the diagram the air pump dump valve circuit is tied in with cannister pruge, lamba inhibit, temp switch at the rear of the water rail, and the air switching module on the right fenderwell. I've never had a 100% firm grasp on how these devices interact or what the sequnce of events is....other than it all begins with the temp switch opening/closing. I've never seen an explanation in any Jaguar manuals, either.

I believe the switch operates at about 157F...can't remember if it's N/O or N/C. It's common for them to be inoperative.

Part of this circuit to to dump air injection pump output after the engine begins to warm up. I suppose cannister purge happens (or ends?) at the same time (a guess) and lambda inhibit ends at the same time (a guess).

Years ago someone on Jag-Lovers came up with a very plausible and complete explanation of how it all worked. I'll see if I can find the info

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David84XJ6 (12-15-2011)
Old 01-07-2012, 09:10 PM
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An Aerospace electrical engineer from my church made the following comments after checking the Diagram and determining the solenoid to have 33 Ohm resistance: "This is a damping circuit to minimize the induced voltage created when the field collapses as power is removed from the coil. Up to 300volts could be in the circuit and Jaguar may have been chasing interference with the EFI ECU or just the radio noise. A similar diode (with out resistor) was introduced across the leads to the GM A6 air conditioning compressor clutch; same model A/C compressor used by Jaguar."

His recommendations for the diode and resistor: Diode IN4936 400Volt 1Amp fast recovery rectifier. Resistor 1/2 Watt 1 ohm Carbon composition resistor

Closest I found at Radio Shack was IN4004 400 volt, 1 amp rectifier diode and 1/2 watt, 1 ohm ??? composition resistor.

It will be a few months before I'm back on the road, cylinder head removal and excessively worn distributor all to be resolved, but will update any additional info collected on this topic then. Rgds,David
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