Jaguar XJ6 (X300) Won't Crank, Just Clicks
On the X300 the starter itself is rarely the fault. The usual culprits are the battery feed through the bulkhead, the starter relay, the switch that tells the car the lever is in Park, and the body processor module. First, though: if the check engine lamp goes out a few seconds after the bulb check, the car is immobilised — a different fault with its own page.
How bad is it · Garage, carefully
Stranded rather than unsafe — unless a connection is burning
Most of these faults just leave the car where it is. The bulkhead feed can burn through from high resistance, because every start pushes the full starter current through it — if you smell hot insulation or see a scorched stud, stop using the car until it's fixed.
Which one applies to yours depends on your symptoms, your model year and what has already been done to it.
Likely causes, most common first
Read the check cost before the odds: a free check that rules a cause out beats a likely guess that costs money.
The battery feed at the bulkhead: a stud or feed-through that has corroded or burnt
The battery is in the boot. Its heavy positive cable comes through the bulkhead on a bolt in an insulating bush, and power posts either side feed the fuse boxes. Corrosion there is fine for dash lights, hopeless for a starter drawing well over a hundred amps.
Clicking with the dash dimming; key-on voltage a volt or more below the battery's; a jump that sometimes works; cruise control dropping out on the move. A stud that wiggles or looks scorched.
Battery disconnected first — these posts are always live. Take off the covers on both sides of the bulkhead and the rubber boot over the starter feed, and look at every contact.
Clean every contact to bright metal, tighten and grease; replace a burnt feed-through bolt and bush — about twenty minutes for a specialist. Check the bulkhead terminal in front of the brake master cylinder too.
The starter relay — and making sure it is the right one
The key switches a relay, which feeds the small wire to the solenoid. A relay can click and still not pass current, through burnt contacts or a corroded socket — and the engine-bay relays look identical, so it's easy to swap the wrong one.
A click under the bonnet, nothing from the starter. Bridging the relay socket's power terminals (Park, handbrake on) cranks the engine at once.
Identify the starter relay from the chart for your year, then swap it with an identical one. A sharp tap can revive a failing relay long enough to prove it.
A new relay in the right position and a cleaned socket; check the relay's coil contact too. On one car a new relay changed nothing until a second relay in the starting circuit was renewed as well.
The gear selector doesn't report Park or Neutral
The car cranks only when a switch at the base of the selector confirms Park or Neutral. With age the switch, or its adjustment, drifts, and the start signal is never sent.
The 'P' on the selector surround glows red when Park is accepted and stays white when it isn't. It starts in Neutral, or after a wiggle of the lever. The check engine lamp stays on, so it isn't the immobiliser.
Try starting in Neutral, and wiggle the lever in Park.
Clean, adjust or replace the linear switch under the selector.
The body processor module — often after water gets in
The body processor handles the start request as well as wipers, indicators, courtesy lamps, locks and chimes. Water from blocked sunroof drains can run down the pillars into it, and its output transistors can fail shorted.
No crank plus a cluster of unrelated things dead: wipers, indicators, interior lamps, door chime, sometimes no remote chirp. The opposite failure: the starter keeps turning in Park or Neutral after the engine starts.
Prove the starter by bridging the relay socket. If it cranks that way and a whole group of body functions is dead, try a known-good used module.
A used module, for example about $50. Clear the sunroof drains before fitting it.
A connector on the way: by the washer bottle, on the fuel tank, at the engine management relay
The start circuit passes through several multi-pin plugs. A single corroded pin or a plug not pushed home breaks it, with nothing else wrong.
It began after work nearby — a fuel pump or battery change — or on a car kept outdoors. Starter and relays proven good.
Inspect the plugs by the washer bottle filler on the right of the engine bay, the bundle connector on top of the fuel tank under the rear shelf, and the feed to the engine management relay behind the right headlamp.
Seat the plug fully, or bridge a corroded pin with a soldered wire.
A tripped inertia switch
The crash switch in the footwell also sits in the ground path of the ignition-fed supply relays. Tripped, it kills a whole set of ignition circuits, not just the fuel pump.
After a knock, work on a lift or a heavy bump. Instrument cluster blank, indicators and brake lamps dead; horn, radio and windows work.
Press the button on top of the switch in the footwell.
Resetting the switch is the whole cure.
The battery after all
A tired battery can light the dash brightly and still collapse under starter load. Rhythmic clunking with the lights dimming in time is the classic sign.
Clunk-clunk-clunk from the starter, lights dimming with each; an old battery, or one that has been flat.
Have it load-tested, not just voltage-read. On the dash voltmeter, a drop below about 9 V while cranking points at the battery or a connection. With the filler caps off, a cell that boils or smokes while cranking is finished.
A new battery.
The engine management computer
The engine computer also takes part in allowing the start. It fails rarely, and usually shows other signs.
No power on the solenoid wire from the key, plus a check engine lamp and misfires once running.
Only after everything above: try a known-good unit.
A replacement computer.
The braided earth strap on the starter
The starter's return path to the battery runs through a woven earth strap. When it frays or corrodes, the starter gets almost no current even though every fuse and relay tests fine — and a brand-new starter behaves exactly like the old one.
A starter that spins happily when fed straight from jump leads but does nothing in the car. A car that has stood for months is the typical case.
Battery disconnected, follow the braided strap from the starter and the engine to the body; look for broken strands and green crust under the eyelets. With the battery back, a jump lead from the battery negative to the engine block is a quick test.
On one X300 a new starter changed nothing, and nor did a P lamp brought back to life by thumping the selector; renewing the braided starter earth did.
The starter or its solenoid contacts
The solenoid can pull in with burnt main contacts, and brushes can stick. The upper starter bolts need the gearbox lowered, so prove it first.
A clean single click at the starter with full battery voltage at its heavy terminal; a tap on the starter body makes it crank. Rapid clicking is too little power reaching the solenoid; a starter that whirs without turning the engine is its drive.
Feed 12 V straight to the solenoid's small terminal, car in Park. If it cranks, the starter is fine and the fault is upstream.
A tap from a jack handle can keep a sticky solenoid going; burnt contacts or a failed starter need a repair or replacement. Getting it out: the top bolt hides under the foam above the gearbox and wants a long extension with a swivel.
The order to check them in
The point of the order is money: each step either rules a cause out or makes the next one worth doing. Green is free, amber costs a little, red is the one to arrive at last.
Key to position II: watch the check engine lamp
Goes out a few seconds after the bulb check — immobilised; see the immobiliser page. Stays on — carry on here.
freeLook at the P on the selector; try Neutral
A white P, or a start in Neutral, points at the selector switch.
freeClean the bulkhead power posts and the starter feed
Battery disconnected first. Both sides of the bulkhead, and the feed-through bolt.
freeSwap the right starter relay
Check the chart for your year; clean the socket.
freeBridge the relay socket or feed the solenoid
Park, handbrake on. If it cranks, the starter is fine — look at the relay, switch, module and connectors.
freeWhole groups of body functions dead? The body processor
Clear the sunroof drains too.
a used moduleOnly then the starter
Have the radio code ready whenever the battery is disconnected.
rebuildWhat it usually isn't
Don't spend money here first:
On jagaux.com
- Jaguar XJ6 (X300) Immobiliser Problems, Won't StartIf the lamp goes out after the bulb check, start there.
- XJ6 (X300) fuse boxes and relaysWhich relay is the starter relay on your year — 1996 and 1997 from the same page.
- Jaguar radio code generatorFree. For when the radio asks for its code after the battery has been off.
- Jaguar XJ6 (X300) Cranks But Won't StartIf the engine turns over at normal speed but never fires.
- Jaguar XJ6 (X300) Gearbox Problems, Gear SelectorLever stuck in Park, loose or clicking at every brake press: the gearbox and selector page.
- Jaguar XJ6 (X300) Headlights Not WorkingIf the headlamps, wipers and indicators died with it — the harness plug on top of the fuel tank.
- Jaguar VIN decoderConfirm your exact model year, engine and factory options before ordering parts — free.
Ratings, fuse numbers and torque figures vary by model year and market. Read the legend on your own car before pulling anything, and use the figures in the manual for your car, not the ones in a video.
Check your VIN: exactly which car you have and which bulletins apply to it.