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  #1  
Old 24th August 2009
travisq travisq is offline
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Default No spark from coil.

Hi. I wonder if someone can help. Yesterday, without warning, my 1986 8v carb 900 stopped starting. I traced the cause to no-spark from the coil. I tried with a new coil-to-distributor lead, then a new coil, then a different ignition amplifier module (in left wing of engine bay), and then a new ignition amplifier relay (D in fuse box), all to no avail. No spark, except, or so it appears, just the one (weak) spark from the coil lead just as the ignition key is turned to start and then nothing no matter how long the engine turns over.

If this means anything to anyone, your help or advice would be much appreciated as I don't know where to take things from here.

Cheers.
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  #2  
Old 24th August 2009
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The obvious things first. Do you have an engine immobiliser on your car alarm? Could be faulty.
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  #3  
Old 24th August 2009
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Try running the car on starting fluid (either). If it wont fire you will KNOW you have no spark.
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  #4  
Old 24th August 2009
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Make sure your Hall sensor hasn't failed. Do you happen to have a spare distributor handy? If so slap the whole thing in and see if it will start. Had a similar problem with my 83 8v turbo and wound up swapping the distributor- fired right up. No signal = no spark.
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  #5  
Old 24th August 2009
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Quote:
Originally Posted by grif900 View Post
Try running the car on starting fluid (either). If it wont fire you will KNOW you have no spark.
Unless your engine is screwed up, like on my 9-3... plenty of fuel, plenty of air and plenty of spark but no vroom!
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  #6  
Old 25th August 2009
travisq travisq is offline
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Thank you for the replies. I don't have an engine immobiliser. I tried fireing her up with starting fluid, no good, and most definitely established the absence of spark from the coil. I didn't check the Hall sensor tho; I wasn't aware it was part of the ignition system. But will do now. Luckily, I do happen to have a spare distributor unit handy so will replace as suggested. Many thanks.
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  #7  
Old 25th August 2009
travisq travisq is offline
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Quote:
Originally Posted by crwchf01 View Post
Make sure your Hall sensor hasn't failed. Do you happen to have a spare distributor handy? If so slap the whole thing in and see if it will start. Had a similar problem with my 83 8v turbo and wound up swapping the distributor- fired right up. No signal = no spark.
Once again, many thanks, crwchf01. Did as you suggested and she fired right up. So it's back to vavavooming for this 24-year old girl (the car, that is, not I).
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  #8  
Old 13th September 2009
travisq travisq is offline
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What do you know? Worked marvelously well for a few weeks and all of a sudden it's happening again : starts on and off and cuts out due to intermittent or absent spark from coil. Once again, changed coil, coil to distributor lead, ignition amplifier, distributor complete with Hall sensor and distributor cap.

Any suggestion as to what may cause the coil to spark and then not to spark would be welcome. Thank you.
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  #9  
Old 14th September 2009
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have a GOOD look at the plug that connects to the hall sensor, they can become fatigued from heat, which causes the wire insulation to crack and sometimes creates a short circuit. you may have to cut away the black rubber boot to see the wires.
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  #10  
Old 15th September 2009
travisq travisq is offline
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Quote:
Originally Posted by ludichris001 View Post
have a GOOD look at the plug that connects to the hall sensor, they can become fatigued from heat, which causes the wire insulation to crack and sometimes creates a short circuit. you may have to cut away the black rubber boot to see the wires.
Did as advised and couldn't see anything odd or wrong with the wires or connection. But then, got the engine going first time after reconnecting the plug. So disconnected and reconnected it again a few times afterwards, but it's still starting and not cutting out, suggesting tweaking of the plug and wires may well have "fixed" the no-spark problem. No doubt I'll soon find out whether it working is a coincidence or, more likely since no part was actually changed or repaired, merely a temporarily fix. I suppose it may be a good idea to change the plug and wires. Does anyone know where the three wires from the hall sensor plug lead to? Thank you.
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  #11  
Old 15th September 2009
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Quote:
Originally Posted by travisq View Post
I suppose it may be a good idea to change the plug and wires. Does anyone know where the three wires from the hall sensor plug lead to? Thank you.
Going from memory, they should go to the ignition control module mounted on the inside left fender. A wiring diagram or simple continuity tester should tell you which ones.

EDIT: See http://townsendimports.com/Web/elect...-90/084-87.jpg

Not your exact model but shows 3 wires, black, green & rown going to pins 3, 5 & 6 of the ignition module resectively. Yours may be the same?
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Last edited by jugganaut; 15th September 2009 at 03:21 PM. Reason: added link to wiring diagram
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  #12  
Old 15th September 2009
travisq travisq is offline
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Quote:
Originally Posted by jugganaut View Post
Going from memory, they should go to the ignition control module mounted on the inside left fender. A wiring diagram or simple continuity tester should tell you which ones.

EDIT: See http://townsendimports.com/Web/elect...-90/084-87.jpg

Not your exact model but shows 3 wires, black, green & rown going to pins 3, 5 & 6 of the ignition module resectively. Yours may be the same?
Many thanks for the info and link. Most useful. It does look close to the way things are configured in my 86 c900. Cheers.

Last edited by travisq; 16th September 2009 at 06:12 AM.
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  #13  
Old 16th September 2009
gotaquestion gotaquestion is offline
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Quote:
Originally Posted by travisq View Post
tweaking of the plug and wires may well have "fixed" the no-spark problem. ... Does anyone know where the three wires from the hall sensor plug lead to? Thank you.
I think that I should try that too. Have a no start problem after doing some engine work. See my post.
Quote:
have a GOOD look at the plug that connects to the hall sensor, they can become fatigued from heat, which causes the wire insulation to crack and sometimes creates a short circuit. you may have to cut away the black rubber boot to see the wires.
I think that I will take a look.
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  #14  
Old 25th September 2009
travisq travisq is offline
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She's not running. Checked every ignition system wire for continuity. Changed every part that (i know) is changeable. Even tried hotwiring ignition at the barrel, grey to green/white wire, in case barrel was source of the trouble. Yet still no spark from coil. In the event, whereas before there'd be intermittent sparking, so she would start now and again, now it's just no spark at all all of the time.

Don't want to let my old 8v carb '86 c900 die though. Been driving a '90 16v injection I keep as a back-up car these last few weeks and not too pleased. Missing the older, more responsive pre-87 c900. So I've been going through this site, and other sites, searching for what may be laying behind the no-sparking from coil, searching for a remedy, but no luck.

Anyone? Thanks.
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  #15  
Old 25th September 2009
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ludichris001 ludichris001 is offline
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this may be a stupid question but i will ask it anyway, when swapping the distributor did you also have to use the original rotor?

also have you checked for spark directly from the coil? (without having it connected to the distributor)

i am only asking because my 900i decided to stop running a few months ago due to no spark. i spent hours on it, my boss at work even had a look at it, then by chance i found that the coil was sparking, bit it wasnt getting to the plug leads, due to the rotor being cracked inside and shorting the spark to ground. replaced the rotor and never had a problem after that

another suggestion of mine:

if there is a wrecker near you with an 8v C900, cut out the wiring for the hall sensor, and ignition module (take the module too) then "patch" it into your C900 as a testing system.
re connect the hall sensor cable (solder it)
connect the blue wire to the - of the coil
green/white to the + of the coil
obviously black to ground..
now turn the ignition on, then connect the + side of the coil to the battery positive and see if it starts
this process is eliminating the the signal and power side of your ignition system
if it still doesnt start then the problem lies within the HT side os the system, i.e the rotor or cap.

hope this helps.

chris
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  #16  
Old 26th September 2009
travisq travisq is offline
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Quote:
this may be a stupid question but i will ask it anyway, when swapping the distributor did you also have to use the original rotor?
Swapped rotor for rotor known to be in good working order.

Quote:
also have you checked for spark directly from the coil? (without having it connected to the distributor)
Yes. Checked for spark holding coil lead (connected to coil) close to distributor body.

I do have another old 8v C900 (wrecked) so spent the afternoon extracting from it the hall sensor and ignition module wiring etc and "patched" it all as suggested. And, what do you know, just like the time before, she started. And has been starting on the button ever since. Not sure why as I'd checked and rechecked all the said wiring for continuity. Now suspect the source of all the trouble may be the ignition module plug. Looking at the one that just came out, the green/white wire metal connector inside the plug seems a little loose, which could lead to intermittent or no contact with the module pin. Will put it back in tomorrow to check.

Many thanks for your help ludichris001. Much appreciated.
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