dui failure - long?

madoc1

 
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i thought might qualify for tech, but if not then chat.
installed a dui in a76/40 in feb./o5. ran great,better than expected.
two weeks ago it was parked after running good. next day would idle, hard to start,missed at higher rpm. did all the usual-plugs,filters,etc. then after two days of messing was lucky enough to kill it completely. (hate intermitent-love totally dead)

finally pulled a plug (last thing since this is a new dui) and saw only a teeny spark. then went to dui,s web sight -their suggestion-buy and throw parts at it at my expense. so borrowed some.
replacement module, no start. replacement module+replacement coil, runs good. so went back in and put orig. dui module. runs like crap, just as it did when this all started.
back to replacement mod. and all is good. theory is bad dui module killed dui coil and would have eventually killed replacement coil.
this is under warranty so should work out, but has anyone experienced this? anyway just another fj saga.

jim
jim
 

Pin_Head

 
 
 
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The trigger module is just an electronic switch, so it is unlikely to cause the coil to fail. Things that can cause both to fail is excessive current (more power = more heat) or excessive voltage leading to insulation breakdown. I don't know anything about DUI, but if you coil is designed to use a ballast resistor, use it as it limits the amount of current that the coil and ignitor sink. Bad high voltage wires and excessive spark gap can lead to over voltage. You only need enough voltage to reliably create a spark. Excess voltage is a waste and can lead to reliablity problems.
 
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What is/was your plug gap? I've heard DUI/HEI users running all the way up to .055. I left mine at .035 and have had no problems in over 6K miles. I have(currently) no ported vacuum, so I only get the centrifugal advance. I think too wide a plug gap and cause early demise of the coil. But I may be waaaay off base here.

Ed
 
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Does an 84 fj60 have a ballast resistor. If so, I just installed a DUI and hooked up the power wire from it to the positive coil wire and I am wondering if I should disconnect it to avoid problems. Everything ran great after install. However a few times, the motor has konked out (wouldn't idle worth a darn). Turn it off and let it cool down and it runs just fine. Thoughts? Thanks.
 
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Not sure, but I THINK that if it is a coil/ignitor setup, which it should be, there is no ballast resistor.
 

madoc1

 
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the plugs were gapped at .o50. new ones are at .o45. dui recommends .o50-..o55.
single wire hookup directly from the batt. via a30 amp relay.

pin i gotca. i thought 4 pin modules were either good or bad. nevertheless this one,(suposedly a superior one from dui) acts strangely. wish i knew. dont want it to happen in the field.

thx jim

thats supposed to say pin i understand.! oops
 
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madoc1 said:
the plugs were gapped at .o50. new ones are at .o45. dui recommends .o50-..o55.
single wire hookup directly from the batt. via a30 amp relay
That's how I did mine, with the exception of the gap. A wider gap....I have heard....is harder on the coil. I have no lack of power or performance with .035


Ed
 

Pin_Head

 
 
 
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madoc1 said:
the plugs were gapped at .o50. new ones are at .o45. dui recommends .o50-..o55.
It will take a higher voltage to jump a wider gap. Maybe that's how DUI sells more coils too?

If there was anything to be gained from running to a very high voltage, don't you imagine that all of the manufacturers would make all their spark plug gaps this wide? It isn't hard to do and it wouldn't cost them any money.
 

Poser

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Pin_Head said:
It will take a higher voltage to jump a wider gap. Maybe that's how DUI sells more coils too?


funny....



pretty sure GM has been using a gap of far beyond .035 for years....
 

honk

 
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Isn't the recommended gap either .055 or .o60 in all GM HEI systems?

Isn't this DUI system just a recurved HEI distributor with GM HEI parts interchange?

Or is DUI really something new and unique?

HEI = High Energy Ignition
 

Landpimp

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yup, just a HEI stuffed into(with the toyota gear....hopefully) a f or 2f.......makes no sense to me......seems like there have been quite of few of these causing more than a little grief......

me.....never had a problem with a OEM Toyota dizzy.....go figure :)

honk said:
Isn't the recommended gap either .055 or .o60 in all GM HEI systems?

Isn't this DUI system just a recurved HEI distributor with GM HEI parts interchange?

Or is DUI really something new and unique?

HEI = High Energy Ignition
 
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Good question, Honk, and I don't know the answer. The reason I gapped mine at .035 is....because....I never changed it due to laziness and the fact that it ran great. I am NOT a wrench or automotive engineer and have no training in auto tech, except what I have learned my screwing things up. But I also think that you don't need a 50 ton shop press if a brass drift will do. I am interested more in reliability than high performance. I've been happy with the HEI, but getting ready to put a new engine in my junk and I am thinking about going back to the Big Cap Toyo. The HEI has performed excellently, given the fact that I had it hooked up to full manifold vacuum(read above pedigree). I have put together a ported vacuum '74 carb and will run both the HEI and "Big Cap" to compare.
Like PH said, what is the point of the gap being so large? Especially if it is causing probs?

So what is causing he problems????



Ed(dumbs***)....but admitting it is the first step
 

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Installed mine in the Red truck, 82-2F, back in '01, gapped the new ND plugs to .055, and ran it. Has worked great since.


Installed one in a '71-40, F engine in '02, gapped the plugs to .055, and has ran great since.


Installed one in the Orange truck, 78-2F, back in '02, gapped the plugs to .055, and has worked great since.


Lemon installed one in the Yellow truck back in '02, 79-2F, gapped the plugs to .055, has worked great since.


Know of at least three other people that have them, and they are working fine.


With this said....





ANYTHING CAN AND WILL FAIL AT ANY TIME.






Sorry to hear of your ignition woes...change out your module, and roll on. Thank you for the heads up...I will now be purchasing a spare coil and module or two...if for some reason, one of these components decides to lay down on me, I will have more backup....


:beer:
 
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So...Steve, are you an HEI fan? I could go either way on this particular question. Do you use the Toyo hold-down or the GM?


Ed
You've given me great encouragement on the HEI, if that's what you're talking about.
 
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i had a similar problem w/ my hei on my pig, finaly after 2 modules and one coil (in 3 months/ 800 miles) figured out that in the rats nest of PO's wiring the GM alt 2 prong plug was backwards... fliped that and no problems since... carl
 

Pin_Head

 
 
 
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honk said:
Isn't the recommended gap either .055 or .o60 in all GM HEI systems?
My '88 GMC with TBI 350 and HEI used a .035 gap.

Here is a pretty good article on ingitions and their pros and cons, including HEI.

http://www.chevyhiperformance.com/techarticles/45618/

The only thing I don't agree in the article with is that they say that increasing the plug gap leads to more efficient combustion. The problem with this claim is that normal ignitions in good condition are not inefficient, so there is little to improve on. The measure of inefficient combustion is the carbon monoxide concentration. A decent engine has a CO value of about 0.2%. Not much room for improvement there.

HEI stands for "high energy ignition", but this does not necessary mean high voltage. Energy means power, and power is volts times amps.
 
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honk

 
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Although the article linked by pinhead concerns high performance applications there are a few things in it that address the questions at hand:

As to a ballast resistor with HEI (DUI) ignition there is this:
"The ballast resistor is used to lower the current to a level that the points can handle without excessive arcing. When emissions requirements in the ’70s dictated lean air/fuel mixtures that were more difficult to ignite, GM came up with the High Energy Ignition (HEI). The HEI is still an inductive-discharge ignition, but it replaces the points with a magnetic pickup and uses a module to regulate the amount of current on the primary side of the ignition—without the need for a ballast resistor. Think of an HEI as an electronic version of a points distributor with the coil built into the top of the distributor cap."

So, no ballast resistor is needed when using an HEI distributor.

And on sparkplug gapping the complete statement contained is:
"One way to improve combustion efficiency with any engine is to increase the spark-plug gap. This requires a higher voltage spark, which can do a better job of igniting the mixture, especially at idle. This comes at the cost of greater demands on the ignition system. Performance inductive and CD systems can handle larger plug gaps of up to 0.045 to 0.055 inch, but this demands excellent performance from the entire secondary side of the ignition system (coil wire, cap, rotor, and plug wires) because of the higher voltage required to jump the wider gap. Typically, this also increases the amperage demands on the ignition system as well"

And:

GM created the HEI as a low-engine-speed emissions-style distributor, so early HEIs were not designed to generate high voltage and current at high rpm (bolding mine). Therefore, the HEI gained a reputation for “laying down” at over 5,000 rpm. High-perf HEI modules offer dramatic amperage increases over earlier systems and can now deliver a hot spark through 7,000 rpm"

"The stock HEI distributor can be modified into an excellent street ignition system with the addition of a matched combination of a high-performance module and coil. Companies like ACCEL, Performance Distributors, Pertronix, Moroso, and others offer HEI ignitions that work very well."


Generally we are not talking about high performance engines when we discuss our F and 2F motors but that doesn't completely remove the advantages of using an HEI system. For one thing, using that system is an easy way to obtain the vacuum advance only offered by selected Toyota distributors. This, coupled with non USA carburation can provide a simple, good running, and reliable engine to those who may have bought a cruiser which had previously been modified by the removal of various elements of the OEM smog equipment. It's one thing to say "keep it stock" but it's quite another thing to find all of the elements required to do so and install them making them work as designed. Also, if there's one thing true about GM parts it's that they are readily available. Anyone can walk into any parts house in the country, if not the world, and buy a new ignition module or a new coil, cap, rotor, or whatever and at a low cost in most cases. It's cheap and easy to keep a stock of "glovebox parts" in the truck, and all it takes is a 1/4" wrench to change most of them.

Personally, I like that big old distributor - I've been in bed with it, figuratively, for over 25 years. (But boy! they weirded us out at first. They would carbon arc all over the cap because of the high energy (current) and when all the promo spoke of the 60,000 volts it spooked even the white guys :D )

The DUI versions were apparently sold with a drive gear made by that company in house or contracted, and that gear, so far as I've been able to tell, has been the source of most every failure of the system. (I understand that they are now providing a Toyota gear) The fix is to get rid of their gear and install one from Toyota. (SOR sells them too, and probably MAF by now). It needs a careful installation and a spacer below the gear per one of the Tech articles in here that's excellent on the topic. Other than that gear using one of the good modules and coils from one of the outfits listed above the system should be as reliable as any other electronic component.

Now, everyone go off and fire up your three gas analyzer so you can see if your engine is efficient or not. :)


edit: http://www.geocities.com/calcide/fj402fhei.html is the tech article I refered to above. (Jeremy Compton, whoever you are, THANK YOU (!!!) for your clearly written and complete articles on various related subjects.)
 
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Here is a question regarding the vacuum source for the DUI. Supposedly the DUI requires vacuum from a port on the side of the carb. Right now that is not a problem with the Holley that came with my 60. However I would like to go back to the stock carb and I don't see a vacuum port on the side of the carb. There are many other ports lower down at the base of the carb but not higher up like the Holley. Will the DUI work with my 84 Aisen carb with regard to the vacuum requirements?
 
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