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Discussion Starter #1
Hello all,
Any help on this problem would be great.
I have read all the threads and found a few similiar problems like the one I have.
The problem I have is unpredictable engine stops. It will just shut off, similiar to turning the key off. Sometimes it will run for miles, others it will die one time after another. This has been going on for a few years!

Items I have replaced:
coil, distributer, pickup coil 2x, balliast resister, starter relay, ignition switch, ECU plug on wire harness, cap and roter.

My biggest problem it that when I go to replace the ECU, the truck will not start. I will then put the old one back in and it will run fine but still have the engine stops as stated before.
I have purchased all the ones from the parts store, but none of them will work. I have many other 70s dodge cars and trucks, none of them work either.
It is such a strange problem but I am sure the problem must be in the ECU.
Last year i was tired of breaking down so I put my demo derby points distributer in and drove for months with no problems. when I look at the wiring diagram i just cannot understand why the replacement ECUs will not work.

The only thing I can think of is that there is a voltage problem somewhere that does not allow the new ECUs to work but for some reason the old one will. Different electronics or damaged ones?

Sometimes after it has died i will try to restart the truck but it will not fire untill the key is turned from start to run. I understand the ballast resistor function and will replace it again. I have replaced the starter relay a few times but they are such poor quality who knows if it is not bad again.

Any one else have this problem? Any help would be gratefull.
Thank you all,
Peder
 

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Love my 66 monaco 500
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Hi progich,
Here is my guess:
There are 2 types of ECUs, the early one with 5 contacts in the connector and a newer type with only 4. The 5th connection is for the wire from the extra ballast resistor. I have ran the 4 wire type with no problems. If you have a problem with that 5th wire and the ECU that kinda runs is a 4 wire type, the 5 wire ECUs you try won't work and the 4 wire one is failing and causing the truck to stall.
Don't forget these ECU need an excellent ground.

Good luck.
Scott
 

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Discussion Starter #3
hi scott,
I have been looking at the wiring diagram after your message. The 5th pin from the second ballast resistor is for the optional speed control. It looks like the 4 pin ECU just gets rid of the speed control pin. I have tried installing 4 and 5 pin ECU before but they all do not work. The only change in wiring that has been done is the plug for the ECU has been replaced. Today I plan to check these wires. Still not sure why the original ECU would work but new ones will not.
Peder
 

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Love my 66 monaco 500
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