Hello all,

I recently redid the brake system on my XJS - removed the MC assembly, rewired the ABS solenoids and swapped the accumulator. I put the key in the preignition spot and 'thought' I heard the pump running however the brake light did not extinguish after about a minute of running. To be sure I was ready to bleed the brakes, I tried to start the engine to verify the pressure would build up in the brakes and it would not turn over. I got a loud, rapid clicking noise, that would persist if the key was held turned. After 5 or so seconds it would shut off the lights until the key was removed and the process was repeated. I checked the wiring near the MC assembly and accumulator as well as the starter relay near the accumulator and all looked good. After letting it sit and turning the key again, the lights went on dimly and no other noise was heard from the engine. I attempted to bypass the relay by jumping the ignition coil wire and the +VE wire which produced a spark but not much else. After hooking everything back up, there is still no clicking when the key is turned. I'm a bit desperate here so please let me know any and all suggestions to try or if there are any tests I can do to narrow it down as I'm a bit stuck on where to go next.

I have read through the sticky on not starting issues, and if it's worth a shot I'll try out the steps there, yet it seems like something is knackered from the poking and prodding of removing the brake components.

 

Hi LAJ

Did you ever disconnect the Battery in the Boot/Trunk ?

If so the Fuseable Link on the Positive Battery Terminal may need Jiggling about or Pushing together

 

LifesAJaaaaaaaag,

It sounds on the face of it as a current problem.

Start with the real basics. What is the voltage of the battery as measured at the battery terminals? Then measure again at the bulkhead terminals. Is there a difference in the readings? Now turn the ignition on - measure again at both points. Is there a significant drop?

In theory, there is nothing that should have occurred as a result of you working on the Actuation Unit (not a Master Cylinder). However, repeated cycling of the ignition could cause a current draw as the accumulator tries to pressurise, and the battery may now be low.

Good luck

Paul

 

OB - I haven't mucked with the battery at all besides the quick disconnect switch, I have checked that fuseable link and it looks good.

Paul - Thanks, I will give that a measure and report back. After several ignition attempts, I did measure the voltage at the terminals and it read ~11V. The voltage at the starter relay +VE measured ~9V. For all the testing I did last night, my battery is now close to flat and I'll need a charge first.

Appreciate the help. Can't help but think there is some stupid nitnoid thing that got impacted by the removal of both brake assemblies on the L and RH side. Hopefully that is the case.

 

LifesAJaaaaaaaag,

Our cars really need a well-charged battery. Anything under 12.5v and you're on dodgy ground. Just running the ABS pump a number of times will drain the battery..

Charge up the battery fully, repeat the voltage tests at battery terminal AND the bulkhead power posts (+ve and -ve). This is very important to check you've got good current conductivity from the back to the front of the car.. If there's anything other than a minor difference of about .1v, there's an issue

Cheers

Paul.

 

You are 100% correct. I was so sure I had mucked something up with the brake install... Turns out that was it, leaving the key in spot 1 for a minute and a half or so must have drained it via the pump to the point where it was just about at the minimum threshold.

I did also go and replace the starter relay with a CR620 as, when I opened up the old one, the contacts had a widely fluctuating resistance. I wrote off the relay as good when I applied a voltage and it clicked. I guess mother Jaguar is a cruel mistress sometimes and it really is the simpler things that should be examined in detail first.

Thanks for the help!