[DML] Scoping out the dwell and RTFM
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[DML] Scoping out the dwell and RTFM



It was a beautiful almost "Spring" day so I couldn't resist.  I 
connected my scope to the diagnostic port to "see" what was going 
on.  According to my calculations the frequency of the signal was 70 
Hz which I believe is correct.  The problem is the duty cycle ON was 
only 38.8% with the WOT switch closed.  The manual says 50 - 60.  
Something did not seem right so I went back to the DeLorean Workshop 
Manual and checked all the "Pulse Ratios" on page D:04:15.  
Everything seemed to be inverted, that is, the lower part of the 
square wave pulse signal got bigger when the WOT switch was closed.  
I tried all the test configurations and the all were right except 
they were inverted.  Attaching a known voltage and polarity to the 
scope proved that + was indeed up.  I was confused. It was getting 
dark and I had to close up shop.  Now sitting here something I read 
popped into my head. It talked about connecting the dwell meter to 
the pinS on the diagnostic plug.  A quick check of the schematic 
revealed the problem.  I had connected my dwell meter and scope to 
one pin on the diagnostic plug and ground. (They way we used to check 
dwell on a car with points.)  It seems that the other pin of the 
diagnostic plug is not ground but rather positive 12 volts.  Thus all 
my measurements were off and I guess I adjusted the CO to around 60 
instead of 40.  Now I have a project for next weekend!

I believe this has been address in the past but none of the answers I 
have found seem to make sense...to me.  When using a DWELL meter to 
measure these "ratios"  What scales and setting do you use?  Since we 
are talking about something that in theory can go from 0 to 100 
percent, it doesn't seem correct to use even the 4 cylinder range 
because that maximum is only 90%.  Does anyone have an answer with an 
explaination?  (I know I am asking alot but remember what the old 
wise man said about giving a fish vs teaching someone how to fish...)

When all else fails Read The Manual.  Fortunately when I was 
flying Pipers I ALWAYS used my checklists and went by the book 
carefully.

Thank you,

Dave and 6530



To address comments privately to the moderating team, please address:
moderators@xxxxxxxxxxx

For more info on the list, tech articles, cars for sale see www.dmcnews.com

To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnews 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
     http://groups.yahoo.com/group/dmcnews/

<*> To unsubscribe from this group, send an email to:
     dmcnews-unsubscribe@xxxxxxxxxxxxxxx

<*> Your use of Yahoo! Groups is subject to:
     http://docs.yahoo.com/info/terms/
 



Home Back to the Home of PROJECT VIXEN 


Copyright ProjectVixen.com. All rights reserved.

Opinions expressed in posts reflect the views of their respective authors.
DMCForum Mailing List Archive  DMCNews Mailing List Archive  DMC-UK Mailing List Archive

This site contains affiliate links for which we may be compensated