[modern] Rev counter

Hi all,

My rev counter has just started to act strangely and wonder if anyone can
offer any ideas/help.

At around 2k rpm, when I accelerate, the needle spasmodically rises to
3/3.5k rpm then drops down to zero, bounces back up to 3/3.5k and drops
again. It will then resume its correct position as though nothing had
happened. During this behaviour, the engine maintains its revs, so the rev
counter is not monitoring the actual condition of the engine.

Is this something to do with the onboard computer system?

Any ideas?

Regards,

Stephen
92 3.2 XJ40 105k UK miles

Check the connection on the ignition coil. The side with multiple
attachments contains the signal info and has a bypassing capacitor to ground
(black rubber top with a wire going into it.). My terminal is on the side
closest to the engine. Its not labeled, but it should be positive, red cap.

Tom Jankovsky-----Original Message-----
From: Stephen Taylor (VBE) Steph.Taylor@Digital.com
To: ‘Modern Jag-lovers’ modern@jag-lovers.org
Cc: ‘John Timberlake’ john_timberlake@hotmail.com
Date: Wednesday, August 04, 1999 3:22 AM
Subject: [modern] Rev counter

Hi all,

My rev counter has just started to act strangely and wonder if anyone can
offer any ideas/help.

At around 2k rpm, when I accelerate, the needle spasmodically rises to
3/3.5k rpm then drops down to zero, bounces back up to 3/3.5k and drops
again. It will then resume its correct position as though nothing had
happened. During this behaviour, the engine maintains its revs, so the rev
counter is not monitoring the actual condition of the engine.

Is this something to do with the onboard computer system?

Any ideas?

Regards,

Stephen
92 3.2 XJ40 105k UK miles

Hi Tom,

After looking at the ignition coil, I am a little confused. I found the LT
leads (Red, and Black with capacitor to ground) that feed the ignition coil.
There is also a form of wires (3 or 4) nearby. Is the signal info delivered
through these, or do you mean the red LT terminal–which seems unlikely?

I’ll have another play over the weekend.

Happy tinkering guys and gals

Stephen & Thu on Cote d’Azure
92 XJ40 3.2 105K miles-----Original Message-----
From: Tom Jankovsky [mailto:TJankovs@fnal.gov]
Sent: Wednesday, August 04, 1999 9:19 PM
To: Stephen Taylor (VBE); ‘Modern Jag-lovers’
Cc: ‘John Timberlake’
Subject: Re: [modern] Rev counter

Check the connection on the ignition coil. The side with multiple
attachments contains the signal info and has a bypassing capacitor to ground
(black rubber top with a wire going into it.). My terminal is on the side
closest to the engine. Its not labeled, but it should be positive, red cap.

Tom Jankovsky

-----Original Message-----
From: Stephen Taylor (VBE) <@Stephen_Taylor_VBE>
To: ‘Modern Jag-lovers’ modern@jag-lovers.org
Cc: ‘John Timberlake’ john_timberlake@hotmail.com
Date: Wednesday, August 04, 1999 3:22 AM
Subject: [modern] Rev counter

Hi all,

My rev counter has just started to act strangely and wonder if anyone can
offer any ideas/help.

At around 2k rpm, when I accelerate, the needle spasmodically rises to
3/3.5k rpm then drops down to zero, bounces back up to 3/3.5k and drops
again. It will then resume its correct position as though nothing had
happened. During this behaviour, the engine maintains its revs, so the rev
counter is not monitoring the actual condition of the engine.

Is this something to do with the onboard computer system?

Any ideas?

Regards,

Stephen
92 3.2 XJ40 105k UK miles