The oneline has the position and the purpose of the fuses and relays. Owner’s manual is good to have but the oneline provided should give you what you need.

 

I'm just gonna wait until my next bit of cash comes in. An old Brit down the street has a Jag shop very close to my house so I'll have him re-index the rotary switch and hunt down the gremlins attacking my transmission relay.

 

I hope it gets you going.

 

Thanks, all! Happy Thanksgiving!

 

Also thought I might mention. If I manually hit the contacts on the relay inside the control box under the glovebox, the car turns over, but for some reason when the tumbler is in the on position, I can't hear the fuel pump running, but there is 12V to the coil... interesting. Any thoughts?

 

The fuel pump not running means one of two things no power or a bad pump. The relay feeding the pump is controlled by the key and is not related to the trans rotary switch fig3A. On Fig6 you can see that the transmission rotary switch controls starting the car via the starter relay. You may be bypassing the rotary switch when you manually control the relay to crank the engine. Get the rotary switch calibrated, check all the fuses.

 

My Jag just started to do the same thing . If i move the shifter slowly while the key is in the start position it was starting for a while now its getting worse. It would be nice to just bypass the rotary switch if possible . A new switch is a whopping $700.00 .

 

omega:
Thought I, given how often these things seem to go wrong (seldom), what are the odds of having two faulty rotary switches? I bought used from one of the online places and saved hundreds. Installed by my mechanic, I think I paid $450; and now it runs like a charm.

I'd buy used.

Scott

 

Make sure you (anyone reading the following) know what you are doing before fooling around with your ECU. Do this mod wrong and you can muck up your cat's ECU and turn it into toast.

Ω man,

Well, if you cannot presently afford what Scott suggests, then read on for apparently a possible "fix".

I stumbled across this the other day, and this seems to be the info you seek.

For a XJ6 VDP 1990 MY

There is an RG (Red/Green tracer) wire from the Transmission Decoder, socket LI45-8, which is an input to the low power side of the Engine Management ECU, pin terminal LI59-3.

What this means is that when the transmission is in any gear but Park or Neutral, 5V is sent to this terminal, LI59-3. Otherwise, it is GROUNDed.

So, it seems to disable it so one can start the engine in any gear, clip the RG wire, tape the end going to the Transmission Decoder and GROUND the wire end leading to the ECU.

I would suggest putting an inline toggle switch here, and label it Start (closed and grounded), and Run (open or ungrounded). I don't know if the 5V signal is necessary when you drive the car away.

Do this in a way so you can easily put this back together again as "Factory" someday.

Let us know if this mod works?

Cheers

____________
¹ a "2" was included in this column when I read the diagram write-up, but I think that is a misprint

 

If you replace the transmission rotary switch is it possible for you to send me the old one?

 

I just got some interesting news from a company in Toronto called British Luxury Auto ph # is 416-693-8400 . He told me that the shift cable on these cars gets siezed and doesnt move properly. He told me to disconnect the cable from the transmission side and exercise it and spray it with lube . He said it should work properly then. This sounds right . I will try this and let you all know the results.