Author Topic: Weak Spark please help  (Read 11142 times)

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Offline Silentstrike

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Weak Spark please help
« on: February 18, 2009, 05:03:57 PM »
Alright so me and my dad have been working on my car for the past week trying to figure this out.  We replaced the carburatuer (sp?) and the distributor coil, the cap and rotor and plugs were new this summer.  We're getting a spark but its weak (orange/yellow tint instead of the white) any ideas?
Thanks
Scott

Offline eroc022

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Re: Weak Spark please help
« Reply #1 on: February 18, 2009, 05:07:33 PM »
did you check the control module located in the distributor ? those tend to go bad....and thats your coils brain
Eroc
Fixing the car that Restore A Muscle Car jacked up....

Offline Silentstrike

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Re: Weak Spark please help
« Reply #2 on: February 18, 2009, 05:11:16 PM »
We were just gonna pull that and take it to advance for tests. any other ideas just in case this doesn't work?

Offline eroc022

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Re: Weak Spark please help
« Reply #3 on: February 18, 2009, 05:13:56 PM »
no not really too much else to check after that....maybe a pickup coil....but i doubt that one
Eroc
Fixing the car that Restore A Muscle Car jacked up....

Offline Rick

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Re: Weak Spark please help
« Reply #4 on: February 18, 2009, 10:40:20 PM »
Unless it the distributor battery wire (the red one) is not fully plugged in or is not giving the distributor a full 12 volts.  Check the battery wire to the distributor to see if it is indeed giving up the full 12 volts. 

Along those lines, about 18 months ago we had a rash of bad ignition switches.  Several guys complained of engines running crappy/not starting and it turned out that the ignition switches had fried their contacts and weren't passing a solid +12 VDC.  They were getting like 5-7 VDC instead.  It was weird -- I bet there were like 3-4 failures in under a week.

Offline ta78w72

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Re: Weak Spark please help
« Reply #5 on: February 19, 2009, 12:59:38 PM »
How old are the spark plug wires?  Does the car start and run OK?  Are you using the correct plugs?  Are they gapped correctly?

From what I've experienced with those modules....either they work or they don't.  But they're a mystery to me because I've never seen a schematic for a module.  The module controls the dwell....that's my total knowledge on those things.

Offline Silentstrike

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Re: Weak Spark please help
« Reply #6 on: February 19, 2009, 03:21:00 PM »
Well I tore it all down last night and turns our the ignition module was tested good but the flyweights on the distributor itself were about to fall off.  We're hoping thats the problem.
Thanks for the advice everyone
Scott

Offline Amtrak

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Re: Weak Spark please help
« Reply #7 on: February 19, 2009, 04:23:06 PM »
make sure the coil has the red and white leads on it

Offline Rick

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Re: Weak Spark please help
« Reply #8 on: February 19, 2009, 08:02:22 PM »
Well I tore it all down last night and turns our the ignition module was tested good but the flyweights on the distributor itself were about to fall off. 

Those are the weights that provide your mechanical timing advance.  You'll want to pay particular attention to their original shape/weight, or else your mechanical timing will be altered.  The springs holding them on are part of the mechanism also.

If they're worn that badly then it's probably time to find a shop with a distributor timing machine and get the distributor recurved.  The factory timing curve wasn't all that fine because it was diddled around for emissions considerations and also done on a mass production scale.  There may be some free power to be gained by having that done.

Offline Silentstrike

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Re: Weak Spark please help
« Reply #9 on: February 19, 2009, 09:51:08 PM »
I got a brand new coil with the right leads and we just decided to go with a new distributor period.  We figured that would be easier since we don't know any machine shops around here.

Offline Rick

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Re: Weak Spark please help
« Reply #10 on: February 19, 2009, 10:05:16 PM »
OK -- keep in mind that the mechanical advance curve that will be in it is a generic one.  They will use the same kind of weights and springs as were used in the greatest number of factory units, and those aren't necessarily the exact ones you want for optimum spark advance in your car.  It will work fine out of the box, but it may well not give you the most power for the fuel you're burning.  Tweaking the advance curve is one of those "tuning" things that is required to get the most out of your engine once it is running well and reliably.  It's the same thing as picking the right rods, jets, and hangers for the Qjet.

When you get the new distributor, check the end play on the shaft.  It shouldn't be more than 0.010" - 0.020" -- the smaller, the better.  Excessive end play will result in spark "scatter" as the shaft bounces up and down with the engine running, and that causes the spark to "jump" around because it's driven by the helical gear on the camshaft.  It's another "fine touch" item.
« Last Edit: February 19, 2009, 10:07:21 PM by Rick »

Offline stimpy

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Re: Weak Spark please help
« Reply #11 on: February 20, 2009, 09:49:55 AM »
question ? what year is the chassis ? as the early chassis have a resistance lead built into the power wire that the HEI cars didn't have and will also cause this problem .

Offline Rick

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Re: Weak Spark please help
« Reply #12 on: February 20, 2009, 08:06:48 PM »
question ? what year is the chassis ? as the early chassis have a resistance lead built into the power wire that the HEI cars didn't have and will also cause this problem .

Good catch, stimpy!  Yeah if the car originally had points there is a built-in resistor in the wiring.

Offline Silentstrike

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Re: Weak Spark please help
« Reply #13 on: February 22, 2009, 04:41:09 PM »
Alright this is gonna sound extremely stupid but there is only one bolt that holds in the distributor right?  My dad and I removed the bolt we could see and it still won't budge
« Last Edit: February 22, 2009, 04:43:07 PM by Silentstrike »

Offline Rick

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Re: Weak Spark please help
« Reply #14 on: February 22, 2009, 04:58:02 PM »
One bolt that holds a clamp, which in turn is what secures the distibutor to the block.  Years of grime and road crap may have "glued" it into place.  Try marking it's location (so you can re-establish rough timing) and then try rotating it to break it free.