Okay so I verified there is no spark. Checked power to the coil, got that. Pulled the distributor and checked the pickup, it tested bad. So since the distributor was pretty fouled up and the vacuum canister was leaking, I went ahead and bought a new one. Installed it and still no spark. On the upside, I finally have a new distributor in there (50 bucks I could've put towards moving, but oh well). So I've got it narrowed down to either the HEI module or the coil. I would imagine if the coil went bad, it would fade out and not just up and quit. For those of you who've had HEI units fail, how did they go? Slow fade-out or did the engine just up and stop?

I have an MSD Blaster 2 coil and an Accel P/N 35361 HEI module, both of which were brand new when I installed them last month.

Now what I'm trying to find out is; is there a good method to test either of these parts individually? I'd hate to replace one part only to find out it's the other that went bad.

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Measure the resistance across the coil primary + and -, then measure the resistance between the coil's secondary output terminal (in the centre of the coil tower) and primary -.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

No, I've had Accel coils just, stop working...I've also had some stock mopar coils just plain stop doing their job one day, too...others just fade and not work as well...


-D.Idiot

From what I understand about HEI's is they either work or they don't, there is no inbetween. The Chrysler box is pretty much the same. I won't get into the debate over which is better, I just know which I prefer.

Coil's I have had go weak. Test as SSD stated, across pos and neg. then neg to center tower, I don't remember the ohm range to look for, but if you find an open circuit, you found your problem. My guess from across the country is the HEI, though....(that GM enginering will get you every time...even if it is aftermarket)

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There are 3 things that will live forever, cockroaches, Keith Richards, and Slant Six Dusters !!!

http://s4.photobucket.com/albums/y128/slantasaurus/

take a look around

Without being there, I'm also going to point my nose in the direction of the Accel HEI module. Accel used to get all their stuff from Echlin, when Echlin owned Accel. Now that's no longer the case, Accel are "shopping for price", and we all know what that means!

The HEI module is an excellent piece of engineering, but if it's not built well of quality materials, it'll fail. Likewise, if it's not adequately grounded or hasn't got an adequate heat sink, it'll fail. How'd you mount and ground yours?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Yeah I'm kind of holding the Accel module in suspicion as well. I don't even remember why I ordered it, since I had bad luck in the past with Accel products on my Toyota. I had the module set against the inner fender "shelf" with heatsink and had a ground strap running direct from it to the battery's ground (while connecting at various other grounding locations throughout the engine compartment as well). One thing I did notice during troubleshooting is that with the factory ignition wire, it's getting about a volt and a half less at the coil than the battery has, and I've read in a couple places that not having full voltage to the HEI module can also lead to premature failure as well. So I'll also add an ignition relay courtesy of this article:
http://www.hoigto.com/tech/powerHEI.htm

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Interesting voltage drop you found! Eliminating the voltage drop can only make things work better and the module last longer, so go for it. The only detail I don't agree with is the guy's choice of an 18ga fusible link in the power feed to the relay's #30 terminal. Fusible link wires are a pain to work with when they burn out, and they're also difficult to select properly to protect any given circuit, since the amperage at which they blow is a function of their gauge and length. I'd use a plain old blade fuse (ATO or Maxi), install something really high like a 20A on initial hookup, measure the current on the line when you start up the car, add a 50% margin, then round to the nearest available fuse value and use that. And carry a spare module and fuses.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I agree with your idea on the fuse. I much prefer fuses and circuit breakers over fusible links anyday. Here's an electrical dolt question though: how can I best measure the current passing through the wire? Just hook up an ammeter of some sort between the wire and fuse?

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Yup! Have you got a multimeter? I have a fairly basic 8-range Radio Shack unit, about a decade old, which contains an ammeter function that'll handle up to 20 amps.

Alternatively...h'mmm. I have the SAE technical paper on HEI from its release in '75, maybe it contains current draw information.

...yep! Says the HEI system limits ignition system current to 5.5A, and has an average current draw of 2A. So you could use a 7.5A fuse.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Groovy. Now to just track down a Bosch 30A relay and holder, and I'll be good to go once I install a new HEI module.

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

You may be able to find one locally. If not I have 'em in stock. Other good brands include Omron, P&B (Potter & Brumsfeld), and if you're feeling lucky, Hella. Pretty much anything made in the 1st world ought to be OK. Be careful not to settle for a no-name Chinese relay; you don't want to add a failure point when you're trying to remove one!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I managed to get my hands on a couple Tycho relays at a local car audio store. I've had good luck with them in the past (have three of them in the headlight harness in my Toyota that've lasted six years so far), so hopefully these will work (one to install and a spare to keep in the glove box) for my purpose here.

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Yup, Tyco's a good brand, even if their CEO did go down in flames for being greedier and more brazen than CEOs are allowed to be (which is very greedy and brazen indeed). Think Tyco bought out P&B.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Well I installed the new module (Napa/Standard HEI module) and wired in the relay, and it runs just fine now. Had to fiddle with getting the timing right because of the new distributor, but everything seems okay now that it's got a new box and has full battery voltage. No performance increase that I could tell, but hopefully the extra volt and a half going into the coil and HEI module will help out a bit with my mileage. Obviously, my primary goal was reliability and the hope of preventing premature module failure in the future. I'll post up some pics when I get the chance to take 'em.

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Jopapa,

Doctor Dodge gave me some good advice earlier this year in my quest for mileage. He said to ditch the 1945 Holley and find a 1920. I did and was rewarded with much better mileage. I went from 16-17 to 22-23 mpg. Jets are super easy to change and the carb doesn't split in the middle like the 1945 which helps eliminate vacuum leaks. The power valve is much easier to tune as well.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG