Good evening Greg,
could you help me please to restore the original connections of the full throttle switch in my 1975 XJ5.3C with Opus Lucas fuel injection?

At the moment the cable is disconnected.

many thanks

Enrico

 

Enrico
If the kickdown switch works on your car like it does on the HE cars, there should be TWO wires going to it. (It may be different on the pre HEs).
Can you see another wire anywhere, not connected?

As well as this, things to check:
The system works mechanically by a small lump on the accelerator cable pushing the microswitch lever at full throttle. If you ask a helper to push the accelerator fully down, do you see the lump push the microswitch arm? Quite often the moving parts jam, or the microswitch arm needs bending in a bit.
The blue shows the microswitch arm
The red shows where the mechanism is that can jam


By the way, those throttle rod nuts should be tightened up to the ends or the rods and throttle butterflies will go out of adjustment. The throttle rods are turnbuckles, one end clockwise, the other end anticlockwise threaded. Adjust properly and the tighten the nuts to lock the rod length.

 

dear Greg thank you for reply, I will check the mechanical linkage, as you suggest, but I don’t have a kick down switch, because the car is a 1975 (n.1064). I can see only one cable from the full throttle switch, the color is brown.

I don’t know how to connect it properly….

Someone could have a picture? Or a scheme?

I already set with a micrometer the throttle bodies and I changed the throttle springs, according to Roger Bywater suggestions, because the car has racing airboxes, air filters, throttle bodies, ecu settings and stainless steel exhaust.

last week I changed the Auxiliary Air Valve too, with the Jag Improver stainless steel one.

I am waiting from Uk the new breather valve with its gasket.

 

Enrico
I do not understand. Underneath that flat plate with the two screws in it, there should be a microswitch. Is it not there? If you need a microswitch, this is what you need:

If your car's kickdown is wired differently from an HE with the GM400 gearbox, you need a wiring diagram. Meanwhile I will ask Grant if he knows about the required wiring for an pre HE.

 

Enrico
I think I have misunderstood your post!
Are you referring to the vacuum operated full throttle switch, or the microswitch operated one, (USA cars have both, UK cars only the Vacuum switch). Please post a photo of the full throttle switch you are referring to.

 

Exactly Greg,
I need the wiring diagram and under the little metal plate there is a switch. The full throttle switch, disconnected.
thank you very much
enrico

 

OK, Greg has communicated, the marvels of the Telephone.

1) The PreHE has Opus Ignition System, AKA, "Hopeless"
2) It also has Bosch D Jetronic Fuel Injection.
2) It does NOT have a Fill Throttle Switch that has anything to do with the EFI system.

That switch under the throttle cable plate is the Transmission Kick Down Switch, and YES, in theory it only works at Full Throttle plus a bit, IF you are blessed. None of mine did, so I removed them and the wires. Fitted a compact Trans Vacuam Modulator, which is adjustable, and let it be. That fitment is NOT simple or easy due to the trans mount is blocking access to it.

ANY Solid Brown wire on that car is Battery HOT. A Black Stripe on that wire is Ignition HOT, which from memory??? was one of the wires on that switch, NEVER a solid Brown.

Somwwhere in my files, I think ??? I have a wiring schematics, and when my one remaining eye permits, I will go looking and post back.

 

Thank you 🙏
waiting for suggestion!

 

hello Greg, the car is UK, VIN 1064, 1975, and doesn’t has a vacuum switch, but only this switch:

 

 

Enrico,

Just to make sure I look for the right PDF's, your car is a Series 2 Coupe, with the 5.3 engine and a BW12 transmission (being 1975), Too many of these older cars have had transplants/modifications/upgrades? etc,, and the lack of into in your threads causes too much guessing, and mistakes, and then upset Jag owners, oops.

Please add your vehicle details to your Sig, as most members have, it is a simple thing, and helps members help you.

 

Thank you Grant,

the car is exactly that you described:

1975 XJ5.3C VIN 2G1064
Pre HE 5.3 V12 engine (original)
Borg Warner 12 transmission (original)
OPUS Lucas injection (original)

The only upgrade is the complete intake/exhaust improvements by Roger Bywater - AJ6 engineering:
- airboxes,
- air filters,
- throttle bodies,
- ecu enhancement,
- stainless steel exhaust with 2 silencers instead of 4.

I will complete the info in my profile.

 

Thank you Enrico.

Being a tad picky, its the Aussie in me, the OPUS is ONLY for Ign Spark, and apart from a pulse signal to the ECU in the rear, has ZERO to do with the Bosch D Jetronic Fuel System (which is purely Analogue). Modern cars are integrated, not these. These systems are the "Grand Daddy" of what we have now, and FAR MORE reliable and robust. Only messed up mostly by humans.
Opus, oh boy, not so, and there was Re-Opus a while back, GOOD upgrade, but now all sorts of systems are peddled, and I will now shut up.

The PDF's I mentioned are attached. If I stumble across any more I will post them here.

Since its 44c and rising, I am off for a beer or 4.

 

Many thanks Grant,
a real mine of informations! Very fascinating.
I hope I can translate the diagram under the bonnet.
I still didn’t found the other end of the brown cable disconnected

 

Give that wire to the dog as a new toy.