Hi All

Need a bit of help diagnosing a no crank on an XJS 3.6 manual 1990 I have just bought please. its a MANUAL gearbox

The problem is that whilst the starer solenoid is throwing out the drive gear, the main motor is not kicking in

I have bench tested the starter & solenoid and it is working correctly, but on the car, the Solenoid is not switching the two 'big' terminals (the ones that will engage the motor itself)

I have 12V going down the ignition wire to the solenoid but at the terminal on the soleniod this voltage drops to 9.4 volts when tested by earthing it to the chassis. I'm thinking 9.4V might not be enough to activate the main motor switch (although the starter gear is throwing out).

Any thoughts on my thinking about the 9.4 Volts.

I'm thinking

- Bad earth off the starter? (should I put another earth from engine to chassis)


Also thinking

- Relay breaking down under load (is this possible even though the solenoid clunks (throws out) every time the key is turned)
- Inertia switch?? (does this effect the voltage if its tripped?)

There are some other things which I would appreciate some guidance on

- There is an additional Brown wire going down to one of the small terminals of the solenoid? Can this cause a problem
- Could there be an alarm on the car (I haven't got one on my key fob)
- Is the 9.4 volts okay/normal - what else could be causing it

Other points to note

- New battery
- engine turns freely
- 12 V direct from battery to to main motor solenoid terminal is good and receiving 12V
- Solenoid and motor have been bench tested and work fine
- I tried another starter and solenoid and the same thing happened (worked on bench but not on car)

thanks

Richard

 

Richard.


1. Indeed, there may be a theft deterent device in the car. But, a bit odd as to allow some part of the required crank protocol, if not all.


2. The "extra" brown wire is unfused battery +, and is a sdource for other loads.


3. As the unit bench tests, I agree, the fault is on board.


4. Do you have a schematic for that car? If not seek one out. Possibly here on this forum. I have one for my slightly different car. Best I've seen and of immense help.


5. If you go down and under, you may find a braided ground strap. At abut where the engine block and transmission meet. In my LHD car on the right side. If so, remove it and clean, tighten and lube it. Jagaur mantra.


6. Grounds are the most popular causes of electric issues. For good measure, remove both cables at the battery and clean the terminals. Lube and tighten. Repeat at the other end of those cables.


7. There is one other test, but I doubt it's need. If so, come back.


Well, come back anyway and report to keep the story going til all is again well. Good for the archives.


Carl