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Author Topic: diagnosing ignition problems  (Read 17127 times)

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f85gtron

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diagnosing ignition problems
« on: March 14, 2014, 07:36:38 am »
what is the best way to check for ignition problems.  on my gt (stock), it seams that number 1 is not firing at the same rate as the others.  i notice slight hesitation when this occurs and i think I've confirmed this using the inductive pickup timing light.  the light flashes rapidly when the pickup is placed from the cap to about 2/3rds toward the plug end, then it flashes at a different rate and dropouts occur past that point.  i placed the pickup on the other wires and they all flashed at the higher rate throughout the length of the wire. 
I thought i was on to something, but since have read that this was not a reliable technique to diagnose a bad wire/plug.
Ron
85 GT manual NOW powered by 7730
3.4 bored to 3.5, cammed out and DIS'd
F23 connecting power to ground
My wife won't ride in it. It's "the other woman" ;)

Fierofool

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Re: diagnosing ignition problems
« Reply #1 on: March 14, 2014, 09:18:00 am »
To test the wire for leakage, start the engine.  Place your right hand on the right shock tower.  Dip your left hand into a pail of water, then slide it along the entire length of the wire.  You will quickly find the point of leakage.  :D

A less exciting way is to pour some of the water from the pail into a trigger sprayer bottle.  At night, away from lights, with the engine running, spritz down the ignition wires.  You should see any leaking wires.  I'd also suggest that you pull the plug for # 1 and see that it's actually gapped at 45.  Remove the distributor cap and look for tracking or cracks on the inside from the area of the # 1 terminal.  Don't use fancy-schmancy double-tipped, platinum or any other higher dollar plugs.  Generally the Fiero doesn't like them.  R42CTS was the standard plug for the 2.8.  I think they were either Champion, Autolite or AC Delco.  I believe the emissions decal on the deck lid will tell you. 

If these prove not to be the cause, try swapping the wire with a spare. 
There are three kinds of men:

1.    The ones that learn by reading.
2.    The few who learn by observation.
3.    The rest of them have to pee on the electric fence and find out for themselves.    Will Rogers

f85gtron

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Re: diagnosing ignition problems
« Reply #2 on: March 14, 2014, 12:52:14 pm »
I've got new acdelcos in it and new 7mm wires, cap, rotor button.  I've had trouble with new wires allot..I'm always suspect of them.   I'll gap them again.  i was thinking it might be more exciting to spritz starting fluid instead of water  :o .
Ron
85 GT manual NOW powered by 7730
3.4 bored to 3.5, cammed out and DIS'd
F23 connecting power to ground
My wife won't ride in it. It's "the other woman" ;)

Fierofool

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Re: diagnosing ignition problems
« Reply #3 on: March 14, 2014, 02:00:10 pm »
Done that.  Problem is that the big flash causes spots before your eyes and it's difficult to tell which are coming from the wires.  The wet hand causes spots, too, but at least you've got a reference point of where your hand was when they appeared. 

My wife had a 73 Hornet hatchback just like the one in the first picture here  https://www.google.com/search?q=1973+amc+hornet&client=firefox-a&hs=Bms&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&tbo=u&source=univ&sa=X&ei=IkQjU7KnC-fx0gHax4HwBA&ved=0CDAQ7Ak&biw=1280&bih=834#channel=sb&q=1973%20amc%20hornet%20hatchback&revid=1072471675&rls=org.mozilla%3Aen-US%3Aofficial&tbm=isch&imgdii=_

V8 engine.  One New England winter, she had trouble getting it started, so she was using starting fluid into the carburetor.  One morning she couldn't get it to run smoothly even after it started.  She remembered seeing me spray down the wires of a 64 Falcon Futura we had owned, with WD40 when it ran like her Hornet was running.  So, not having WD40, she used the starting fluid.  Fortunately it turned out to be the coil and not the wires she had sprayed. 

Have you compared resistance of the various wires with a meter? 
« Last Edit: March 14, 2014, 02:22:28 pm by Fierofool »
There are three kinds of men:

1.    The ones that learn by reading.
2.    The few who learn by observation.
3.    The rest of them have to pee on the electric fence and find out for themselves.    Will Rogers

f85gtron

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Re: diagnosing ignition problems
« Reply #4 on: March 14, 2014, 04:40:28 pm »
that's funny.  good thing she didn't get hurt! I'll check resistance this afternoon.
Ron
85 GT manual NOW powered by 7730
3.4 bored to 3.5, cammed out and DIS'd
F23 connecting power to ground
My wife won't ride in it. It's "the other woman" ;)

f85gtron

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Re: diagnosing ignition problems
« Reply #5 on: March 14, 2014, 05:58:20 pm »
Ok. resistance checks out.  wiggle test shows nothing....resistance holds steady, but i did find this plug, not suspected #1, that appears to have traces up the insulation.  could this be it, or am i knit picking?
Ron
85 GT manual NOW powered by 7730
3.4 bored to 3.5, cammed out and DIS'd
F23 connecting power to ground
My wife won't ride in it. It's "the other woman" ;)

f85gtron

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Re: diagnosing ignition problems
« Reply #6 on: March 14, 2014, 06:18:47 pm »
measured the coil. getting .8 between secondary and 8.43 on a 20k ohm scale for the primary....primary should be like 10, right?
Ron
85 GT manual NOW powered by 7730
3.4 bored to 3.5, cammed out and DIS'd
F23 connecting power to ground
My wife won't ride in it. It's "the other woman" ;)

Fierofool

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Re: diagnosing ignition problems
« Reply #7 on: March 14, 2014, 10:53:52 pm »
I would have suspected a trace on the insulator underneath the boot.  Some carb cleaner should clean up anything.

I don't know what the resistance should be on the coil.  I'll bring along a spare.
There are three kinds of men:

1.    The ones that learn by reading.
2.    The few who learn by observation.
3.    The rest of them have to pee on the electric fence and find out for themselves.    Will Rogers

f85gtron

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Re: diagnosing ignition problems
« Reply #8 on: March 19, 2014, 05:55:05 pm »
I cleaned and reinstalled the plug.  Loosened and pulled the wires at the cap to watch the spark and look for misses....saw none.  Everything looked good.  While standing back to cuss a bit, i noticed a bit of popping and could see arcing at the base of the plug, so i guess the electrode and/or insulation are broke.  So, i found my problem and hope to be able to get back to Miata killing soon.
Ron
85 GT manual NOW powered by 7730
3.4 bored to 3.5, cammed out and DIS'd
F23 connecting power to ground
My wife won't ride in it. It's "the other woman" ;)

f85gtron

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Re: diagnosing ignition problems
« Reply #9 on: March 23, 2014, 10:00:34 am »
Update:
After replacement of the suspect plug, it immediately ran MUCH stronger.  Curiosity got the better off me, so i ran to harbor freight an got me on of those telescopic inspection mirrors to look at the front bank for the same conditions as the rear.  I found another arcing plug, so back to napa to make ANOTHER exchange.  I went ahead and bought a coil too.....while i was at it.
I think the whole problem stems from the salesman dropping some of the plugs on the floor when bringing them to the counter.  We opened them and checked them visually, but i guess they broke inside. Oh well, lesson learned ;)
Ron
85 GT manual NOW powered by 7730
3.4 bored to 3.5, cammed out and DIS'd
F23 connecting power to ground
My wife won't ride in it. It's "the other woman" ;)

f85gtron

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Re: diagnosing ignition problems
« Reply #10 on: March 23, 2014, 10:04:12 am »
Oh yeah, an checking your ignition system with an inductive pickup is a worthless pursuit.  It lead me down the wrong path entirely. 
Ron :-[
85 GT manual NOW powered by 7730
3.4 bored to 3.5, cammed out and DIS'd
F23 connecting power to ground
My wife won't ride in it. It's "the other woman" ;)

Fierofool

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Re: diagnosing ignition problems
« Reply #11 on: March 23, 2014, 03:21:44 pm »
I told you to dip your hand in a bucket of water.  :D
There are three kinds of men:

1.    The ones that learn by reading.
2.    The few who learn by observation.
3.    The rest of them have to pee on the electric fence and find out for themselves.    Will Rogers