liquidpower

hey guys and girls,

i keep having this problem with my 70 98. i upgraded the distribute to http://www.jegs.com/i/Proform/778/66955/10002/-1?CT=999 and swapped out the power wire to the coil to give it the full 12 volts(no more points). the coil has power going to it. but some days i dont get spark and the car wont start so i go out and buy an new coil put it in and then it starts up. so far iv been threw 4 coils. funny thing is tho last week one died and i still had an old one laying around so i poped it back on and it worked but now 9 days latter it no spark as i try and go get dinner at work . any ideas whats going on.

thanks

J-(Chicago)

Check the pick up coil wires.

Bluevista

I know it may may be a longshot but does the coil have constant power or switched power going to it?

MDchanic

A few questions to begin with:
Is the engine original or modified?
If modified, how?
How did the old distributor work?
If the engine wasn't modified, why did you put a high performance distributor in it?
Is the wiring original (other than the change you made)?
How did you make the change you made to the wiring? What way did you make your connections?
What sort of coil are you using with that distributor?
How many miles or days does a coil seem to last?
Why have you believed the problem was the coil?
Do you still have the original distributor?
How does the engine run when it is working?
Does it ever die while it is running, or do you just go out and find it won't start?

- Eric

joe_padavano

If an old coil that you thought was "dead" started working again, then obviously it's not the coil. Check for a broken wire with an intermittent connection. Unfortunately, the break could be anywhere in the circuit.

MDchanic

Absolutely true...

... but if changing the coil "fixes" it, it's most likely to be in a location that is jostled by the movements associated with changing the coil .

- Eric

liquidpower

well the engine is original.If the engine wasn't modified, why did you put a high performance distributor in it? the reason i did this was because the points where going out of dwell and that threw off the timing so i wanted to get rid of the points.

sort of coil are you using with that distributor?
first it was just the adv discount auto brand then i got a mds coil.

when working the engine is running fine.

im beginning to think that it may be the distributer not giving the signal to the coil. is there any way to test this. when i put the old coil back it it only lasted 2 or 3 days Normie if i put in a new one it will go for about a 4 to 6 months.

the coil and disy are wired up with the diz plugged in to the coli and the coil getting the 12 volts from the ignition

MDchanic

It's water under the bridge now, but I would have bought a $5-10 set of points rather than a $200 distributor. Partly it's because I'm cheap, but partly because when you start changing things, other things go wrong, and it's much harder to figure out.

It is exceptionally unlikely that all of these different coils would be bad.

This helps to narrow things down with a bit more confidence.

The coil is being fed 12 volts from the ignition switch, through the wire to the (+) terminal. That current goes through the coil, into the distributor, and then to ground when the distributor tells it to. The On / OFF oscillation of the distributor is what induces and times the high voltage. In a points system, this is done by a little switch (the points). In an electronic system like you have now, it is done by a little computerized doodad. Neither of these can create extra current and damage the coil.

You can test the distributor by attaching a SMALL light bulb (like an tail light, NOT a headlight) to a 12V source (like the wire at the coil (+) terminal), and to the distributor lead (disconnect one coil terminal to remove the coil from the circuit). The light should flash on and off as you crank the car. This is not a definitive test of whether the distributor computer module is good, but should give you an idea. It is also easy to do at the side of the road without disturbing anything else. If the light either stays lit all the time or doesn't light up, then the module is bad.
If the light flashes, then the module is PROBABLY good.

- Eric

liquidpower

i guess the strangest part then is why dose changing the coil always fix the problem. i have a circuit board that i have maid that sends square waves that i can use to test the old coils

ill use this to look at 2 of the old ones i have if there busted this will let me know.

MDchanic

So long as it can push about 10 amps without burning up.

Check the resistance - I don't recall now, but I believe GM coils are pretty low resistance - as low as 1.5Ω. At 14 volts, that's nearly 10 amps.

You might do better with a set of points and a condenser, and a way of measuring the maximum gap the spark will jump through (be careful not to get zapped!).

- Eric

liquidpower

ya the power supply for the 555 timer is a 12v 40 amp it should handle the coils i made it to run 4 coils at a time and boy did it make a awesome plasma arc. i will test all of the old coils tomorrow and let you guys know what i find. now for the power wire that i had to replace. i used a regular electrical connection and i saw that the old one was a bit longer what i used was like this [[IMG]file:///C:/Users/jasonb/AppData/Local/Temp/moz-screenshot.png[/IMG]http://www.2carpros.com/how_does_it_work/images/wire_connector.jpg] Is that OK do you think that might be hitting something else and shorting out the coil

MDchanic

Not likely shorting the coil, but I'd solder those connectors, rather than just crimping them.

As for 40amps, your power supply may push 40A, but do your switching transistors?

If you've successfully run 4 automotive coils off of it, it should be fine, but if they were 4 small "coil on spark plug" coils, it's a different story.

liquidpower

ya the thin i posted the pic of is just the digram for the 555 timer (like this http://www.eleccircuit.com/ignition-...ic-555-2n3055/) the power supply is a lab power supply that can put out the amps and the 4 coils that i used 2 where 2 msd Blaster 2 coils and then 2 coils that i found in a junk yard like the type in my distributor. next up date will be with the results of the test. and some pics if i get them to spark

liquidpower

well it turns out that it was the distributor i had to recheck my circuit and there was a blown capacitor replaced it and it made all of the coils work so i put in a older one and moved some of the wires under the distributor cap and got the car to start right up this Saturday ill pull the distributor and solder all the wires. ill try and put some pics up of that as well as testing the sparks.

CutlassDad

Just before storing my son's '70 Cutlass S (350 short deck T350) we replaced the points ignition with a Proform HEI...

The coil is in the cap of the HEI...

We ran a 12 ga wire from the IGN terminal of the fuse block
(switched 12V) to the HEI, and used the TACH lead for an RPM indication (long story about the tach).

Ran perfectly.

Can't wait 'til spring (SE Wisconsin).

Gerry

miked

Sorry if I'm a little off subject but when replacing the stock points dist (67) with a GM hei do you have to mod anything for the stock ralley pak tach to be accurate? Mine operates but I'm not sure if it is correct. Thnx, Mike

CutlassDad

We used the typical rectangular box tach/dwell tester tach function just to get a tach reading to set the timing.

If you connected a 2nd tach, the rectangular box tach/dwell tester comes to mind, you would be able to compare the two...

droldsmorland

Grounds Grounds Grounds! Clean all the grounds. Make sure there is a good clean ground(s) to the engine block via the battery negitive cable as well as a braded ground strap from the head to the firewall if so originally equiped. Cant hurt to install one for good measure.
The new electronic distributors will fry modules and coils if there isnt a good ground path. In a negative ground system the voltage will seak the path of least resistance and will usually fry sensitive pc boards and electronics. Some manufacturers even suggest a suppression box be installed between the voltage supply and the dist or coil to catch transient spikes. A 40 year old car likely needs many if not all of its grounds cleaned. Get a diagram of your car and start going through it. Doesnt hurt to spray clear drying(verses the stuff that stays wet) ignition sealer over the bolts once you've cleaned the connection.

miked

Good suggestion on the dwell-tach....thnx. Now if I can just remember how to use a dwell-tach after all these years...ha
Mike