91 XJS, Intermittent problem. When turning key to start position the car will lose all electrical power. All dash lights as well as all interior lights. If I remove the positive battery cable and reconnect right away, the power is restored and the car will start. This may happen 1 out of 8 or 9 starts. It is as if something is being rebooted. Very frustrating. Any ideas? Rick
PS; I'm a newbie to this forum.

 

This could be tackled from various directions.

Personally, I'd begin with the basics:

- Battery connections clean and tight

- Battery ground cable clean and tight where it bolts to the body in the trunk

- Ground strap at engine clean and tight. On my '88 XJS this was near the LH motor mount

- Clean, tight connections at the two "+" voltage junction posts on the firewall. Power for all the systems is distributed from these posts. They're a little hard to find....look on the fiewall inboard of, and below, the brake booster for the LH post. Symetrically the same for the RH post. They'll have rubber boots over them.

Cheers
DD

 

Oh.....forgot my manners !

Welcome aboard

Cheers
DD

 

I had the same problem recently, I had it happen one time when I had a voltmeter handy and was able to read 13 volts at the battery but only 2.5 volts at the high voltage protection module.

The problem was a poor wire crimp at the battery terminal. I was able to recrimp the cable and cure the problem. If you don't have a crimper that large a new battery cable would be in order.

 

Welcome Rick.......... XJS ownership is an illness that is terminal.

Back to your issue. Turn on some lights, interior will do then grab the battery cable and give it a good tug, also down the RH side of the battery there is an area where all of the grounds are bolted to the car check here for loose connections.

 

Thanks Guys, Can someone tell me what the 2 brown wires just below the positive battery terminal connector goes to. Or what the purpose is.

Rick

 

I would bet dirty/corroded earth if I had to. The wires you mention might well run up to the fuel sender, I had some run in that general election but then again mine also had a horribly installed aftermarket alarm which made a pig's ear of the area... The guru's on here will know more - and btw welcome

 

It could be a shot ignition switch.

 

Probably nowhere there are a couple of what seems superfluous wires there. Any brown wire has 12V on it.