[s-cars] Bad Coilpack? Coilpack wiring test?

[Robert Myers]

The coil has +12 volts present at all times (ignition on).  The ECU 
triggers the PSO channel which shorts the other end of the primary of the 
coil to ground.  This creates a pulse of current in the primary and, in 
turn, produces a magnetic pulse.  The magnetic pulse induces a high voltage 
in the secondary of the coil which fires the plug.

Possible faults:

1.      Lack of +12 volts at the coil.  This voltage comes from the 
firewall connection to the coil (the other end of the harness from the 
PSO).  Pull the connector and check that +12 volts is present at the 
connector for coil #4 (or all of them if you can't identify #4).

2.      Wiring through the coil is not continuous.  Check the resistance 
between the two coil connectors (PSO and firewall).  It should be low - an 
ohm or so.

3.      Failed PSO channel.  Swap the two PSO units with each other and 
locate the miss again.  If the miss stays with #4 the PSO is not the 
problem.  If the miss does move then channel #4 has failed.  If the sixth 
channel has not already been used you can move the #4 wires to the #6 
position.

4.      Failed secondary.  This is basically what's left if everything else 
is OK.  It's time to swap in a new coil.  Rewiring completely is a bit of a 
chore but it is fairly easy to cut and splice and retain the wiring 
harness' external parts.


At 07:29 PM 5/11/2005, Nathan Belo wrote:

>Car has been missing, so I swap out plugs & coil lead connectors for new
>ones to no avail.  So I swap out POS & do the pull the electrical connection
>to the injector test to find out #4 cyl. is not firing.  I've replaced POS
>twice already & it appears I bought an extra one that I don't need now. I
>pull the plugs & all of them have carbon deposits except #4 which is shiny
>brand new.  I talked to SJM & he said normally he sees failed coils under
>high boost, so I test for spark by grounding the spark plugs onto the valve
>cover like SJM said.  Sure enough no spark to #4.  Bad Coil?  Is there a way
>to test if there's a wiring problem?
>
>I had this problem last year about this time & it mysteriously fixed itself.
>
>How hard is it to re-wire a new coilpack?  I can see that the wires go to
>the plastic plug on the firewall.
>
>I have 169K miles.
>
>--
>'01 Ducati 750 Monster Dark, like the owner & I ride naked!
>'92 Audi //S4 IA III+ w/95.5 S2 (CGR) 6-spd Pearl/Ecru
>Nathan Belo
>Associate Broker (Residential, Commercial, & Business Opportunities) &
>Notary Public
>Skyline Properties, Inc.
>9709 3rd Ave NE, Suite #500
>Seattle, WA  98115
>206.686.8989 Accessline Voice/Fax
>
>"Brake later & open the throttle before normal"- Valentino Rossi
>
>
>
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