No Spark

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Steve
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No Spark

Post by Steve »

Hi all,

Sorry if this has been covered before but scouring the forum and the Internet doesn't seem to be helping so thought I would ask a bunch of humans :D

Took my car for a drive a week or so ago, started and ran lovely. No issues. Parked up, went to start a couple of days ago and she turned over but no hint of wanting to fire.

Quick check and no spark from the HT lead from the coil. Coil is a Blaster 2 as I have a GM style four pin HEI conversion (no ballast resistor).

I did the usual checks. 12v to coil + in run position, 12v to HEI unit, good earth to HEI, continuity through loom seems OK. Wires to distributor seem fine, rotor turning so distributor shift OK.

Changed HEI unit (2 spares and tried them both), changed coil, changed HT lead, hot wired coil to be sure direct from battery. Nothing. Still no spark.

As I'm on my own I've been using a remote starter to turn the car over so leaving the key in run position and using the starter from the starter relay to check for a spark.

I'm a bit lost for ideas now and my head is thinking it's the HEI unit as that's the only thing that I think can be working one minute then not the next. I've tried the 2 spares so unlikely to be that.

I'm sure it's a simple thing that I've overlooked, any ideas as common sense seems to be evading me at the moment,

Cheers Steve :read2:
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Steve
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Re: No Spark

Post by Steve »

Forgot to say one thing I haven't done is to check the reluctor gap in the distributor. Can this suddenly go out of adjustment and if its wrong, will it prevent the car starting or will it just make it difficult to start??
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Re: No Spark

Post by Steve »

I also haven't checked the power to the coil + in 'start' position as I don't have enough hands. I take it that with the key in the 'run' position, when I engage 'start' with the remote button, it's just the same as turning the key to 'start'?

I also haven't checked to see if there is voltage on the - side of the coil as I've (wrongly maybe) assumed the coil is OK. Am I correct in saying a small reading is OK buy anything anywhere near 12V would indicate a duff coil??
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Re: No Spark

Post by Pete »

Start and run only matter if you are running a Ballast Resistor.

Disconnect all the wires to the coil and test its resistance - if it is open circuit then the input sides of the coil have failed.

More difficult to test the HT side...
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Steve
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Re: No Spark

Post by Steve »

Thanks Pete, is that a test between the inside of the HT socket and the + terminal on the coil?

Cheers Steve :thumbright:
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Re: No Spark

Post by Pete »

No. Between the "+" and "-" ve terminals with all the wires off....

Do you not have a spare 12v Coil (or any coil in the short term) you can use? That would be the best way.
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Re: No Spark

Post by Steve »

I've changed the coil Pete and it hasn't helped. I'm not sure why it was running perfectly when I parked the car up then next time I go to it it there's no spark.
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Re: No Spark

Post by Pete »

Sorry, I missed that point....

It's a head scratcher....
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Re: No Spark

Post by Steve »

I'm going to check the reluctor gap tomw and take it from there. It's got to be something small that's broken or moved to make it OK one minute to not working the next if that makes sense. Thanks for your help Pete,

Cheers Steve :thumbright:
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Re: No Spark

Post by Pete »

I have not worked on an HEI set up (other than on Chubbies at work) so not sure how this is wired.

However, on an MSD unit, you can disconnect the output wires from the Dizzy and if you short out the wires to the Amplifier / ECU with the power on, it will produce a spark - thus proving it on or off the Dizzy.

It may be worth trying this on your set up to see if it helps diagnosis.

In my opinion it is pointing to the Dizzy and maybe the reluctor has failed (uncommon but it could happen) or it has been bridge by coming loose against the "chopper".
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Re: No Spark

Post by Steve »

Brilliant Pete, that's certainly something for me to look at tomw. It's wired exactly as the standard HEI upgrade a few years ago and has worked a treat ever since...
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Re: No Spark

Post by MattH »

I would suspect the module, we had Mandie's one fail on her Chevy truck whilst on the NSRA supernats cruise. Luckily had a spare at home and got towed there by a Ford pilot, changed it over and were back on the road in an hour or so.
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Steve
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Re: No Spark

Post by Steve »

Thanks Matt. I have 3 HEI modules and have tried all 3 with no luck. 3 coils, no luck and now beginning to think it might be distributor related?? Think I would be unlucky I'd all 3 HEI units are faulty but not un heard of. The one I've had in for years is a USA made one but the two 'get me home ones are cheaper Chinese ones. Would make sense as you suggest as they either work or they don't and my fault is related to working one minute and not the next so its not a gradual breakdown of a component.

I'm tempted to try and find a Pertronix unit somewhere and try that.

I checked the reluctor gap and it was out a bit ( should be .008" and was .016) so quite a difference but still no spark.

Thanks for the advice Matt. All adds to the bigger picture for me...cheers
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Re: No Spark

Post by MattH »

We are sure it was the module, but for ease we had a complete distributor which we changed over, 1 bolt and one wiring connector, rather than lots of dismantling.
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Re: No Spark

Post by Dave999 »

If you have a multimeter
set it to very low AC volts

connect to the 2 pickup wires from the dizzy, and spin the dizzy, or turn over the motor on the starter
if the pickup is good, you should measure a small AC voltage as it spins, 0.5 volts to 2 volts

You could also try measuring its resistance, if its infinite or zero, you have a failed pickup.

given everything you swapped, this is the only thing i can think of.....

or your reluctor is loose on its shaft. tiny roll pin fell out... unlikely, the dizzy needs to have completly knackered bushes, and drive, and the internals need to jig up and down many times a second, for that to happen


HEI modules and failures.

having had 2 fail in similar circumstances in the last two years
this is my hypothesis (some of it formed from a discussuion on wireing alternators up ,in race cars, that i had at the HRDs, some race cars have complex wiring set up, loads of switches and fuses, others very simple )

so i my mind
If you stall the car, during cold running, (in my case reversing on grass out of a deep hole, at santapod, on a cold wet morning without letting it warm up and stalling it at about 1500 rpm) or indeed trying to leave the line, when prenteding to drag race, and stalling it at about 3000 rpm , after having driven it stop start down the fire up lanes for an hour (i'm not pushing it)
AND
the battery is quite flat
AND
the alternator is full ON charging the battery, 1500 rpm or more with a flat ish battery, Ammeter pegged at the 30 AMP pin
THEN
the action of stalling the car casuses the massive magnetic field generated by your alternetor when it is FULL ON to collapse. in a manner much the same to what happens in the ignition coil when it creates a spark.

with an old style basic alternator this causes a massive voltage spike in the car electrical system

which takes out your HEI module. either instantly or it dies within a week.

my thnking is that the HEI module saw a big negative, potentially Kilovolt, spike at its + terminal and it doesn't like it at all.

mitigate this with a diode in + supply. put a 1n4007 in + lead, and if the car works, you got the diode the right way round, if it doesn't turn it round the other way.

you could also stick one the opisite way round in the negative lead, but that might stop the control of the coil so the module can then not switch it on to off

(i.e not sure if the module switches off the coil, by breaking its earth connection, or by shoving 12 volts up its negative connector. both would cause a spark due to magnetic field collapse in the coil. 2 ways to cause a coil to spark, both involve 0 volts across it. one is to break its connection at + or -. no circuit so no current so magnetic feild collapses and you get a spark.
the other is to match the voltage the coil primary sees at + and - . A coil with +12V at both + and - is OFF in the same way a coil with 0 Volts at + and - is off. and i don't know what the modules do. it could be either method

also note
we don't run a condencer like they do on the chevys and a condencer (a capcitor that can store charge) would take the pointy edge off the spike, it would end up chargeing the condencer rather than blasting through some sensitive circuit in the module, and go some way to protect the module from whatever internal shorting or burn out it receives in this circumstance


Dave
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