164 LS Coil Problem Help needed

[Bernie & Diana Bennett <bennetts@domain.elided>]

Digest members:
We are still trying to diagnose the failure of the coils (now two -- one
on each cylinder bank) of my 164LS. Please carefully read the details
below and see if you have any useful input or comments. If you know of
someone off digest I can call who is an experienced diagnostician or
experienced with the 164LS / Quad (1994 /1995) US.
Below messages are to and from a variety of correspondents.

Thanks for any help,
Best Wishes,
Bernie Bennett
Brenham, TX USA
409 836-1302
bennetts@domain.elided



On another matter, my 1994 164LS automatic is still off the road (since
July 17th). I will be posting another query to the digest this
afternoon. The car is still blowing coils. Takes less than a minute to
fry them after starting the engine. Diagnosing the cause has got my
repair shop in Austin puzzled.  I'm going to reread the 164LS Service
Manual to help me understand how the fuel injection/engine ignition
system works. What could cause a coil to overheat? melt and crack in
about a minute. Was always the same cylinder until we swapped power
modules. now it's blowing that one plus another on the right cylinder
bank.

Here's some history, & thinking out loud. I'll use some of this to post
to the digest

July 09---

Ignition Coil failure--
Anyone have any guesses as to why it failed?  I hear that this is rare
(47,000 miles)?  Car began to have a loping idle, run rough down on
power and noxious exhaust.  Diagnosis (thanx BJ at Alfa of Austin) by
removing fuel injector electrical plugs (old style have metal spring
clip retainers) easy to lose).  (Note: Remove plug to idle solenoid (or
whatever it's called) behind engine first. Or the car will not react to
one injector being disabled) Get an assistant to start engine and
operate accelerator as engine will not run with this disconnected.
While diagnosing, the coil went into final failure with a burst of
acrid smoke from below it's cover. Ignition shutdown and the smoke
subsided.
Removal of the cover showed a cracked ceramic bakelite 'coil' which had
begun to melt.

20 July--
>
> 1.  Replacing the coil did not fix my problem.  Engine still ran rough

and coil melted in less than two minutes!  Any ideas?  The car is going
on wrecker to Austin to the Alfa Service place.  But if you have any
diagnositc ideas to help them out?  What was the nature of your failures

on the Aston Martin?  Just bad coils or a wiring thing. ARI/ARDONA said
they had the wiring in the coil circuit burn up (coils OK? I think?) all

the way back to the ignition switch? Again any thoughts?
- -- Here was suggested putting an ocilloscope on the coil to see what was

happening (it happens so fast I don't know that's doable.
- -- Also suggested maybe what's happening is the coil is getting voltage
that's way too high an it (the voltage) is breaking down the system?

Sep 4
- -- I was hoping to report with good news; but I got word yesterday that
with the installation of the coils, and the new ECU and swapping the
power modules(to diagnose if the power module was bad) the car now blew
two coils (one on each bank.) So we now have more information; but are
back to square one.

The following offer in response to the above Sep 4th message has been
taken under advisement:
- -- Another suggestion: If you think the problem is in the static coil
harness somewhere (I doubt it but where do we look now...), I'll be glad

to send you what I have (goes from coil to connector on engine toward
firewall). This step has not been taken.

Other suggestions made by various multiple sources. Coils fail if spark
plugs go bad. -- In the most recent episode, Italian Motor Service
cleaned and tested wiring, replaced all spark plugs.

Possible Valve problem (why would the problem migrate & multiply).

What do you know about the "FIAT tester"? Would it be of help in this
diagnosis.

Thanks for letting me bend your ear.

Best Wishes,
Bernie Bennett





    Subject:
          Coil Problem
      Date:
          Sun, 12 Sep 1999 20:54:08 -0500
      From:
          Bernie & Diana Bennett <bennetts@domain.elided>
 Organization:
          Bennett Family
       To:
          ferdinando di matteo <ferdinando.di@domain.elided>
  References:
          1 , 2 , 3 , 4 , 5 , 6



Thanks for the quick reply. Yes, OEM (but all used coils New have not
been
available as Alfa has been moving back to FLA.)

So how would I check the primary voltage w/out frying the meter. Can we
check with the bad coils installed?
Would that then indicate a bad power module? Or What.

I'll be forwarding your insights / suggestions to my service providers /

mechanics.

Thanks, Bernie

ferdinando di matteo wrote:

> Bernie, the only thing that can melt a coil is a too high a primary
> voltage or a shorted secondary.  I suggest you check the primary
voltage
> to the coil that was fried, you should get a reading instantly when
you
> start the car.  Were the coils OEM to begin with?  Fred


Fred also suggested getting the battery voltage with the engine running.

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