hi guys
i have a 1995 4.0 auto when trying to start it the lights come on but it doesn't crank sometimes if i wiggle the gear knob or put it in neutral she starts also when i put my foot on the brake there is a clicking from under the gear lever
any ideas thanks

 

Hi and welcome, the most likely cause will be the "not in park switch" sticking. I'm going on memory but I think you will have to remove the gear surround to access it.

When you get chance, drop into the new members area and introduce yourself.

Hope this helps,

Jim.

 

hi jim is the switch called j gate linear switch
many thanks dave

 

Could well be. Should be somewhere near the front of the J gate.

 

Hi, on my RHD car, the switch is located underneath the ski slope (the wood panel that runs down from the radio and surrounds the gear shift) on the right hand side of the gear shift. There are numerous write ups in the archives, by myself and others regarding the removal of the ski slope and how to sort this problem. If your car starts when wiggling the gear shift, that is a clear sign that the little micro switch has gone out of line.

This switch only allows the car to be started in either Park or Neutral, for obvious safety reasons. Do a search "Not in Park switch" or similar and you'll find all the answers you need.

 

Next time the 'no crank' happens observe if the "P" in the gear indicator dial is glowing red. It should be; the starter won't crank if it isn't. Now, jiggle the gearshift. Did the "P" turn red? And the starter now operates? If yes, you probably need to adjust your linear switch

The linear switch is #29 in this picture


http://www.jaguarclassicparts.com/uk...trol-automatic

Loosening the screws is a little tricky but then it's just a matter of sliding the switch fore-n-aft to find the sweet spot where the "P" glows red without any jiggling.

The nomenclature is conflicting between service and parts manuals. The service manual shows a 'linear switch' of for the 3.2, 6.0 V12, and supercharged cars while the 4.0 non-supercharged has an 'encoder module' (or something like that'. The parts manual calls it a 'linear switch' in all cases, it appears.

The 4.0 normally aspirated cars also have a transmission mounted rotary switch but I'll have to let others comment on that as I'm not very familiar with it.

As far as I know the 'not-in-park' switch functions only on the gearshift interlock circuit and has no bearing on the starter circuit....at least none that I can easily see in the diagrams. It allows the gearshift interlock solenoid to operate (and make that click) when the gearshift is in "P" but disables the circuit at all other times. Without this switch the driver would have to listen to the interlock solenoid click whenever the brake pedal was pressed.

Cheers
DD

 

Doug wrote

As far as I know the 'not-in-park' switch functions only on the gearshift interlock circuit and has no bearing on the starter circuit....


That's also my understanding. The Linear Switch/Decoder module provides a Park/Neutral signal to the BPM. The BPM then provides a ground signal to the starter relay (assuming other start conditions are met - Check Engine light etc.)

 

I was out of the Jag for 3 weeks due to the same problem. Had just completed some suspension work and mysteriously it wouldnt start. Turned out my battery was run low, due to boot/trunk courtesy lights staying on (due to a faulty switch in boot/trunk locking system that also sends signal to dash warning light that A door is afar). So the low battery voltage had put the security system into a shutdown/lockdown (not sure of proper term describing this state) mode. Once battery was brought up to proper state of charge and slow charge conditioned, all was fine, for a few days. Then, it happened again. This time going into trunk to fetch some tools, noticed the court. lights did not illuminate, replaced bulbs (found sockets discolored from getting hot), did some research on the locking mechanism (as my dash door ajar light was still coming on) and found this switch. Located the switch in the boot/trunk locking mechanism/circuit and found it broken and defective (it's a Ford switch, so easily found), replaced switch, and also installed a manual switch in-line to operate lights, reconditioned battery again, and reset alarm system (enter cab, close doors and trunk! insert key, turn to on, and turn off), and all has been fine- this was last February I think. I believe what I'd found out was that the low voltage detection leads the computer to believe the security system is being tampered with or and attempted bypass, and it then locks out the security system until the condition is remedied.

I gone through the shifter trouble-shooting steps as everyone has correctly suggested here, also checked the brake pedal (depresseing it should click the switch inside the shifter housing underneath fwd center consul (you should hear a click), as well as the park light glowing hot red. All was well here. I just happened to find a post about the security system lockout here in the JF's, and then happened upon my boot lights burning out and curiously further investigating the locking mechanism there to find it. I love my Jag, but sometimes Daphne is really attitudinal about her upkeep!

So, this is just something to keep in mind if your preliminary systems checks prove normal. I'm pretty fortunate, aside from a few console lights I need to replace, the clock display unreadable, and of course the typical radio display lights inop, everything electrical works as it should in our 1997 XJ6.

Hope you are up and running soon. Some gread advise in these columns, and they usually lead you in the righ direction and issues are resolved properly.

 

Many thanks for that very useful post. It's often the mysterious, less obvious, undocumented issues that cause us so much head scratching! Glad you got sorted and maybe others can benefit from your experience.

Thanks again.

 

In order to have the most efficient use of language, this problem might have been better titled a "Cranking" problem rather than a "Starting problem".

In the car context, "Cranking" is generally considered the operation of the starter motor to turn the engine.
"Firing" generally refers to any cylinder , well, firing. "Starting" refers to cranking, firing, then running after the key is no longer in the start position.