Finally found the cause of my over-richness. - Jaguar Forums - Jaguar Enthusiasts Forum

Go Back  Jaguar Forums - Jaguar Enthusiasts Forum > Jaguar Models ( Classics ) > XJS ( X27 )
Reload this Page >

Finally found the cause of my over-richness.

Notices
XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

Finally found the cause of my over-richness.

 
  #1  
Old 03-17-2019, 07:02 AM
JigJag's Avatar
Veteran Member
Thread Starter
Join Date: Mar 2016
Location: North Carolina
Posts: 1,201
Thanked 467 Times in 304 Posts
Default Finally found the cause of my over-richness.

Punchline is something to do with Jaguars. Pa-dum-pum kssshhh!

Actually, my full-throttle micro-switch was broken.



Thereís your problem right there.

Internally shorting. So, full throttle enrichment all the time! Anyone know what the % increase here is? I know that if you run the ECU full lean and drop the fuel rail pressure to 18 psi it counters this enrichment. So, quite a bit.

Iíve no idea when this switch failed, Iíd tested it middle of summer or so and it was functional. Very glad to have found it finally. The connection boots covered this area and hid the cracked case.



 
The Following 4 Users Say Thank You to JigJag For This Useful Post:
darrhel (03-18-2019), Doug (03-19-2019), Greg in France (03-18-2019), Mac Allan (Yesterday)
  #2  
Old 03-17-2019, 11:24 PM
Join Date: Feb 2010
Location: Adelaide Stralia
Posts: 18,798
Thanked 5,452 Times in 3,928 Posts
Default

Sooooo, not your Right foot then, HA.

About 15% is the figure bantered about, but I have never measured it.
 
The Following User Says Thank You to Grant Francis For This Useful Post:
JigJag (03-19-2019)
  #3  
Old 03-19-2019, 03:17 AM
Crackerbuzz's Avatar
Senior Member
Join Date: Jul 2018
Posts: 186
Thanked 34 Times in 29 Posts
Default

I wondered what this was...

Does this bang in more fuel when this is triggered?
 
  #4  
Old 03-19-2019, 04:04 AM
darrhel's Avatar
Senior Member
Join Date: May 2014
Location: Perth, Western Australia
Posts: 135
Thanked 9 Times in 7 Posts
Default

Hi, how do you test the switch.....?

Rgards

Darren
 
  #5  
Old 03-19-2019, 06:32 AM
Veteran Member
Join Date: Jan 2012
Location: France
Posts: 8,802
Thanked 4,330 Times in 2,768 Posts
Default

Originally Posted by darrhel View Post
Hi, how do you test the switch.....?
The circuit and the switch is normally open. At full throttle it closes and that triggers full enrichment. Just use a test light see if the switch is passing current or not when it is in its normal state with the throttles closed, and if it does when the microswitch lever is activated by your finger - which is what the capstan does when at WOT. this is one of two devices on the car (USA spec only, UK just have one such device). The second device is a vacuum switch (on the cabin end of the A bank inlet Manifold) which is held open by manifold vacuum when the car is running at anything but WOT.
 
The Following 4 Users Say Thank You to Greg in France For This Useful Post:
darrhel (03-19-2019), Grant Francis (03-19-2019), JigJag (03-19-2019), kjopen (Yesterday)
  #6  
Old 03-19-2019, 08:22 PM
JigJag's Avatar
Veteran Member
Thread Starter
Join Date: Mar 2016
Location: North Carolina
Posts: 1,201
Thanked 467 Times in 304 Posts
Default



Easiest test for this switch is to trip it by hand with the car idling. If you idle changes significantly then the switch works and so does your vacuum-based WOT switch if you have one.

As Greg said, the micro switch is normally open and the vac switch is normally closed but held open by 1 in. of vacuum or more. Both switches provide a ground to pin 5 on the ecu when activated.

Proper test ( 16cu ECU )
Checking pin 5 with the car off should show a ground. If not vac switch is bad.
Disconnect the vacuum switch electrical connectors and pin 5 should NOT show a ground. This confirms the wiring.
Tip the micro-switch and pin 5 should show a ground. This confirms the micro-switch functions
Reconnect the ecu and start the car. Now, at idle, reconnect the vac switch.
No change in idle confirms the vac switch opens.

Unless, that is, the micro switch casing is cracked and flexing, but is held together by the rubber boot on the side connector. Then the end connector can shift and close the switch. it may be intermittently shorting and at other times not. This could go on for more than a year and almost drive you mad.

Thats is the real reason for the post. I just wanted to give a heads up that this can happen, and be hard to detect.

Heres a closeup of the broken micro switch. You can see that the missing piece was not bonded to the case base. Only the corner of the case top was holding this corner together. And the side connector flexes against it when the switch is tripped. Eventually that case top edge failed. The top is less than a millimeter thick. Poor design choices here by Burgess. Current micro switches are beasts by comparison. But this one did last a long time!

When I say top and base I’m referring to the photo. The switch is upside down in the photo. When mounted, none of this was visible.





 

Last edited by JigJag; 03-19-2019 at 09:19 PM. Reason: Add a picture
The Following 3 Users Say Thank You to JigJag For This Useful Post:
darrhel (03-19-2019), Greg in France (Yesterday), kjopen (Yesterday)
  #7  
Old Yesterday, 02:26 AM
Senior Member
Join Date: May 2018
Location: Hunua
Posts: 157
Thanked 35 Times in 27 Posts
Default

I purchased some after market limit switches from RS Components
842-1745
Both normally open and normally close.
Choose the right combo - holes line up perfectly.


 
The Following 2 Users Say Thank You to Dukejag For This Useful Post:
darrhel (Yesterday), JigJag (Yesterday)
  #8  
Old Yesterday, 11:11 AM
JigJag's Avatar
Veteran Member
Thread Starter
Join Date: Mar 2016
Location: North Carolina
Posts: 1,201
Thanked 467 Times in 304 Posts
Default

Thanks for that link Dukejag! I was digging through Google results and this helped me filter them. But I think I'm gonna drop some serious dough ( $11 ) on this Honeywell environmentally sealed version for use in Zone 2 hazardous locations. Not that I'm worried about this switch causing an explosion, but simply for the sealed case and robust design. I'll modify the mounting slots to accommodate the lever length if they do not offer a longer replacement roller arm.


 
 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
JessN16
XJ6 & XJ12 Series I, II & III
6
01-27-2019 06:51 PM
Jagboi64
XJ XJ6 / XJR6 ( X300 )
29
08-30-2017 11:09 AM
nebigjohn
XJ XJ6 / XJR6 ( X300 )
2
08-14-2015 11:47 AM
Dan Bennett
XJ XJ6 / XJR6 ( X300 )
9
09-30-2013 09:32 AM
magredvet
XJS ( X27 )
9
06-17-2012 03:47 PM

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 

Thread Tools
Search this Thread
Quick Reply: Finally found the cause of my over-richness.


Advertising
Featured Sponsors
Vendor Directory

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: