Giving up on the DUI

62Ranchero200

62Ranchero200

Famous Member
Background: A DUI was part of my 250 w/AL head from the beginning, and had been running for about a year when the issues started. The DUI was custom curved for my engine and ran extremely well when it ran. I've put only about 2,000 miles on this engine since it was new a year ago.

About a month ago, on a Saturday afternoon as I was getting into the Ranchero, GF in the passenger seat to go to a local cruise-in, the Ranchero started, but ran very roughly. After a wrong turn looking at the power valve and diagnostic testing, I finally determined that a faulty DUI module ($50) was to blame. The module was diagnosed by elimination as there is no at-home test you can perform on an HEI/DUI ignition module - the voltage to the DUI, ground, coil, and magnetic pickup all tested within spec. After I replaced the module, the Ranchero ran well again for a month.

Last Saturday, again the Ranchero failed to start. This time, I did as much diagnostic testing as I could, replaced the module (another $50), but the Ranchero still wouldn't start. Replaced the coil as well (although it tested within limits, 0.7 Ohm primary 7.8 KOhm secondary) (another $50), to no avail.

The magnetic pickup tests within spec - 1040 Ohms, generated .5 - 1.0 V when the distributor is rotated - but that's significantly more trouble to replace - have to pull the distributor, pull the gear, pull the shaft out the top. I don't own a press so pulling and reinstalling the gear would be a PITA.

Two failures within a month, and $150 in parts so far, and the Ranchero is still not running ...

So I'm switching to a more traditional MSD / DS II setup. The DUI is too unreliable, too difficult to troubleshoot, too difficult to repair, and parts are too expensive.

Thanks
Bob
 
A DUI system is just a modified GM HEI system is it not?

If so, I'd strongly encourage using only AC Delco modules. All the other ones are lowest-bidder garbage. Assuming you have the proper thermal paste installed and voltage/ground are all within spec, I'd personally suspect low quality HEI modules. HEI powers bazillions of GM cars - it's pretty darned reliable.
 
thesameguy":q4uc1cn3 said:
A DUI system is just a modified GM HEI system is it not?

If so, I'd strongly encourage using only AC Delco modules. All the other ones are lowest-bidder garbage. Assuming you have the proper thermal paste installed and voltage/ground are all within spec, I'd personally suspect low quality HEI modules. HEI powers bazillions of GM cars - it's pretty darned reliable.
Click to expand...

Low-quality modules may indeed have been the cause of both of my failures. If that's so, then the replacement module I installed this past weekend must have been faulty right out of the box. I wasn't buying generic auto parts store modules - both of the replacement modules I purchased were Accel. I'm not sure that I believe that GM necessarily has better quality control procedures than a specialty aftermarket manufacturer like Accel.

I do believe that specialty aftermarket ignition control boxes, such as the MSD 6A, may be manufactured to higher quality standards than replacement HEI modules. For the cost of three to four HEI replacement parts (modules or coils, $50 each), you can buy an aftermarket ignition control box ($150 - $200).

Finally, I think that having to pull the distributor, pull the gear, and pull the distributor shaft to replace the magnetic pickup in an HEI distributor is unacceptable; I believe that you can replace the magnetic pickup (although not the reluctor) in a DS II without doing any of the above.

The crux of the issue is whether an MSD 6A, for example, proves more reliable than HEI modules. The total cost of both systems is almost exactly the same, although there is more wiring required with the DS II / ignition control box.

Thanks
Bob
 
I support your decision to ditch it.
They are big and ugly. And so is the MSD. DS2 for the win! (y)
Reliability is important to me.
 
62Ranchero200":2uqcdlz5 said:
thesameguy":2uqcdlz5 said:
A DUI system is just a modified GM HEI system is it not?

If so, I'd strongly encourage using only AC Delco modules. All the other ones are lowest-bidder garbage. Assuming you have the proper thermal paste installed and voltage/ground are all within spec, I'd personally suspect low quality HEI modules. HEI powers bazillions of GM cars - it's pretty darned reliable.
Click to expand...

Low-quality modules may indeed have been the cause of both of my failures. If that's so, then the replacement module I installed this past weekend must have been faulty right out of the box. I wasn't buying generic auto parts store modules - both of the replacement modules I purchased were Accel. I'm not sure that I believe that GM necessarily has better quality control procedures than a specialty aftermarket manufacturer like Accel.

I do believe that specialty aftermarket ignition control boxes, such as the MSD 6A, may be manufactured to higher quality standards than replacement HEI modules. For the cost of three to four HEI replacement parts (modules or coils, $50 each), you can buy an aftermarket ignition control box ($150 - $200).

Finally, I think that having to pull the distributor, pull the gear, and pull the distributor shaft to replace the magnetic pickup in an HEI distributor is unacceptable; I believe that you can replace the magnetic pickup (although not the reluctor) in a DS II without doing any of the above.

The crux of the issue is whether an MSD 6A, for example, proves more reliable than HEI modules. The total cost of both systems is almost exactly the same, although there is more wiring required with the DS II / ignition control box.

Thanks
Bob
Click to expand...

On my 1986 F150 w/4.9L engine, I have used MSD 6A with the original square ignition coil for 6+ years with no issues. The MSD box was used [free] and was available when I removed the feed-back system. The distributor is a re-curved Duraspark unit.
 
Thanks to ALL,
good info
nice thread
keep er goin...
 
62Ranchero200":23580e41 said:
I'm not sure that I believe that GM necessarily has better quality control procedures than a specialty aftermarket manufacturer like Accel.
Click to expand...

I think you'll find they really do, especially vis a vis Accel. Most people in GM land avoid Accel modules because they are, in fact, pretty low quality. When it comes to stock replacement parts, folks like MSD and Accel aren't doing the manufacturing - it's just lowest bidder production with a fancy box and a price premium. You should see the outrage on various GM forums about the quality of MSD HEI distributor caps, for example. I use MSD coils in both my Fiero and my XR4Ti and they've been great, but their plastic pieces are garbage. I don't think you'll find anyone who recommends anything other than AC Delco HEI modules, in the same way you won't find anyone who recommends anything other than Motorcraft TFI modules. They really are made to a higher spec.

Do a quick Google search for "Accel HEI module" and you'll get mountains of pages with reviews like:

I have not heard anyone have long lasting history with Accel products. We had an Accel dist in my sons truck and it self destructed in about 4 months,,,,out of town of course!
Click to expand...
I ordered this module as a replacement from the stock version I had on my 1988 Chevy Pickup, after it went bad. I took the old one out cleaned up the mess that was on the distributor, put on the new "heat sink grease" that came with it and put everything back together. It fired up right away. My truck ran good for a little over a year and I had to replace it again. This time I went to Napa auto parts and bought the OEM style and it's been there for around 3 years now. Maybe I got a bad one from Accel, don't know, but it didn't last like it should have.
Click to expand...

The crux of the issue is whether an MSD 6A, for example, proves more reliable than HEI modules. The total cost of both systems is almost exactly the same, although there is more wiring required with the DS II / ignition control box.
Click to expand...

I am definitely no fan of HEI. I think it's better than Ford's TFI, but neither are "good." I'm sure the MSD solution will provide excellent reliability and the cost is definitely far from prohibitive. There's certainly no reason not to do it! My only point was that DUIs *should* be reliable, and the issue is almost certainly low quality modules. :)
 
I just checked the MSD website for an MSD DS2 , zip. and MSD apparently does not make a dizzy for our 6's. I'm ready to build a 250 for all out drag racing, what to use? I dunno.
 
use a good later model stock DSll distributor. they are stone cold reliable, and if you want a module other than the ford one, go with the chrysler orange ignition box, again stone cold reliable. i used that combination along with an msd blaster lll coil and it lit off first time every time, even with a suspect carb, and in 30 degree weather.
 
I use the OEM dizzy in 1978 engine , 200... Hooked to an Accel digital ignition box and coil. Works well for many yrs. Accel discontinued this system


MSD will replace it , when it fails
 
rbohm":hsg15nyb said:
use a good later model stock DSll distributor. they are stone cold reliable, and if you want a module other than the ford one, go with the chrysler orange ignition box, again stone cold reliable. i used that combination along with an msd blaster lll coil and it lit off first time every time, even with a suspect carb, and in 30 degree weather.
Click to expand...

I have to agree on this one 100% .
 
That's why I sold off my brand new one that was sitting in a box for years. Plus they are so huge next to our engines.

DSii, msd box and msd coil. Perfect combo for me.
 
Bill (wsa111) has custom curved a DS II for me (the 250 likes 20 degrees of initial timing, so my total advance needs to be limited) and this was shipped Saturday. I should receive it mid-week and will order an MSD ignition box and Blaster 2 coil.

It will be a while before the Ranchero runs again because I also have a small fuel leak - I think it's the accelerator pump diaphragm - that I need to fix before I drive it again.

Thanks
Bob
 
80broncoman":1ihu9jwf said:
rbohm":1ihu9jwf said:
use a good later model stock DSll distributor. they are stone cold reliable, and if you want a module other than the ford one, go with the chrysler orange ignition box, again stone cold reliable. i used that combination along with an msd blaster lll coil and it lit off first time every time, even with a suspect carb, and in 30 degree weather.
Click to expand...

I have to agree on this one 100% .
Click to expand...


Interesting to note: the Performance Distributor ignition module is the same as the Mopar module.I sold my DUI and purchased a DSII from the same company, Performance Distributors. I even purchased a set of their Live Wires for my boat. Anyways, my DSII ignition system performed great for 2-3 years until a coil when out. And a year later, I'm tracing a stall or dead short where the engine just dies for no reason then starts right up sometimes without having to pull over.

The Mopar orange modules are less that $45 on Summit. I'm buying one as a spare. Can't beat the price.
 
While not a DUI, but its the same reason I stopped using the Pertronix and went DS2 when the P2 nearly left me stranded and running on 3 cylinders limping home. Standard over the counter parts. And I never needed to replace them anyways. The DS2 is hard to beat, both in reliability, durability, and price for performance.

Generally I'm a fan of stock ignition system designs. On my current build, most likely going Ford EDIS.

Regards,
 
Bill (wsa111) had some concerns over the versions of the Pertronix too. Outsourcing Least Cost Option engineering never wins long term.
 
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