I have a 1974 duster and the problem I am having is with my ECU. The one on my car is the original and is a 5 pin, my dilema is that all the ones I am finding are 4 pin. does this make a difference or can I just replace mine with a 4 pin module and not have any issues?
Thank you gentlemen for your aid.

 

Bolt in the 4 pin ECU and go, but while you're at it, check the reluctor gap in the dist. O' Reallys actually stocks brass feeler gauges. You need a .008". That is INCHES, not mm


Here's the story on 4/5 pin ECU's

The older design 5 pin ECU's require the old style 4 terminal ballast

The newer design 4 pin ECU's WILL REPLACE the 5 pin modules directly, and only NEED a 2 terminal resistor, but WORK with either 2 or 4 terminal resistor.

(The "other half" of the 4 terminal resistor is simply not connected)

Also, you can NOT tell some brands of replacement ECUs by just looking. Many 4 pin ECU's STILL HAVE 5 pins, it is simply that the 5th pin is not connected, so if you need to know, you must use a meter and check continuity from/ to the 5th pin

If you look at these simplified diagrams from "MyMopar" you'll see that half the resistor and one wire were eliminated in the 4 pin ECU design

from this page:

http://www.mymopar.com/index.php?pid=31

What is NOT shown in these diagrams is the brown "resistor bypass" wire for starting, which connects to the coil + side of the ballast resistor

The old 5 pin design. The left half of the resistor and the wire connected at the bottom were eliminated in the 4 pin:



and the newer 4 pin:

 

Thank you, you just answered what 4 dealerships, and several technicians could not. Thank you very much. Time to get my baby back on the road......

 

???? DEALERSHIPS and SERVICE TECHS??? Damn..... sounds like a brush off from them to me... Service Techs maybe, if they are younger ones, but still... damn

 

9 years later and I am fighting the same issue I bought a 1972 d100 that was sold with electronic ignition because it’s a California truck and the wiring has been butchered over the years neither of these diagrams show the voltage regulator were they not used? Thanks Scott

 

I found a 5 pin on eBay for 19.99

 

am I correct that this diagram doesn’t show the brown/ black wire?

 

Shouldn't have any problem using the 4 pin

 

I have a 1973 Dodge Challenger that I have been having problems with keeping spark if loses it completely and some times intermittently I’ve tried a lot of things including a wiring harness still no spark any ideas and would it be simpler to convert it to points

 

X -

Have you tried replacing the ECU, voltage regulator and ballast resistor(s)?
Assume the dist cap and rotor are new?
Points might solve the problem, but then you have "points".

Archer

 

I Agree... Change the ECU to the Orange box..... Dont forget to clean the grounds and install new star washers when installing the new ECU.... Keep us posted...

 

HEAVY on cleaning those grounds. my fury would die out of nowhere, at speed sometimes. took me foreeeever to find the issue, which was the actual box itself wasnt touching bare metal. i took it off, chipped paint with a screwdriver, put it back on, and it stayed lit after that. that was a tough gremlin to chase down!

 

I think I remember that?

 

lol, you likely do. that was a scary *** week.

 

thanks for been so helpful and took from your time to answer and that encourage me to post my problem too.