Weak Spark?

1921 Views 6 Replies 3 Participants Last post by craig w., Apr 4, 2006

craig w.

Discussion Starter · Oct 7, 2005

Had what appears to be ignition troubles at the track last night. I've seen this before with a weak coil/not enough box. It ran fine on the motor, but would cut out on the nitrous. Its a Programmable-7 7530 box and HVC coil. Worked fine a couple weeks ago. Now the spark looks a little weak, but sounds pretty hot and will jump a gap of about an inch. The spark is white/blue on the ends but a little orange in the middle when its jumping 1/2"-1". Closer than that distance and its blue. It sizzles and sounds good though. Sound weak to you all or is it OK?

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Sparky

· #2 · Oct 10, 2005

I have seen the HVC Coils jump about a 2 1/2" gap and blue all the way, christ you could almost weld with it.
You may want to call MSD and ask them what the resistance between the primary's should be. I know they did have some trouble with the primary circut on the HVC coil.
Couple of questions, Is the Band around the coil grounded? It should be. How old are the Plug wires? Anything over a year should be replaced. What is the Gap on the plugs? Anytime you shoot Nitrous to an engine, you should tighten up the gap.

Letme know,
I hope this helps
Sparky

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craig w.

Discussion Starter · #3 · Oct 10, 2005

I tried a new coil and its pretty much the same...runs like crap on the bottle. On its last run, it was 7 tenths slow in the 1/8th.

I compared the resistance of both coils and they were pretty close. 2.1 ohms for the "old" one and 1.8 for the new one.

The band around the coil is grounded. I re-did all the grounds for the entire ignition system and the motor ground strap as well last week. Didn't seem to make much difference.

The plug wires are a year old, but not many runs since I didn't get the car out until June of this year.

In order to help crutch the problem, I narrow the plug gap up to .020 from the .025" I ran last time out. I shouldn't have to run narrower than about .030" I don't believe. I know guys that are running a lot more nitorus than me with the same NGK -9 plug that are running .030" gaps.

I'm going to send the 7530 box back to MSD to have it check out and have my alternator and battery load tested. I had some starting problems as well, so system voltage is now on my list of suspects.

Thanks for the input. I appreciate it.

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Sparky

· #4 · Oct 10, 2005

Voltage could hinder your problem as well, If the car runs ok on motor, maybe once you introduce Nitrous, your dropping voltage due to the added load. So, maybe you need to look at what kind of voltage your at running down track with and without Nitrous.

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craig w.

Discussion Starter · #5 · Oct 10, 2005

Good idea. It seems to run fine on the motor. It runs about as fast on the motor as it does the bottle! Thanks.

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Doc Holiday

· #6 · Apr 3, 2006

Did you ever get this problem sorted out? This is the exact problem I am having right now.

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craig w.

Discussion Starter · #7 · Apr 4, 2006

I haven't sprayed it this year yet, but I will this Saturday. I think the problem is solved though. It was a combination of low voltage due to a bad connection from the alternator to the battery and the new distributor cap and/or rotor I put on it last fall was crap. First run last Saturday, it still cut out at high rpm and was way down on mph. I changed the cap and rotor and all is well. Picked up from 102 to almost 108 mph in the 1/8th on the motor.

So I think its all cured now.

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