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B200 Issue
#666351 July 16th 2014 2:23 pm
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rider Offline OP
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Hi all,

My 79 B200 keeps burning up Ignition control modules about ever 300 to 400 miles. Anyone have any idea whats going on?

Re: B200 Issue
rider #666670 July 22nd 2014 3:56 am
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pooh-bah
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Hi Rider, are they actually dead?

What I'm wondering is that if you put one which you already pulled out for failing back in if it would in fact work?

A couple of things you might consider - the big ceramic resistor on the firewall can go bad /intermittent. They read about 1.2 Ohms on an Ohm meter.

Also, the metal case of the ECU is used as electrical ground, and if the connection to the firewall is poor it will fail to work, but not necessarily kill the module. Swapping in a new one makes the ground connection temporarily,so the new module appears to cure the problem, until the ground corrodes or loosens again, then it fails again. It is almost always worth cleaning up the case of the ECU where the bolts go, and applying some Silicon dielectric grease to the underside of the bolt heads and threads to reduce corrosion by moisture. If the bolt holes through the firewall are stripped, relocate the ECU slightly and drill new holes for the bolts. It has to be a really good,solid ground.


-It's been such a LONG TIME... BlueShift>> 1981 Dodge Ram B250 Custom Sportsman Maxi Van


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Re: B200 Issue
Ram4ever #666675 July 22nd 2014 8:25 am
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I agree that a good electrical ground is a good idea for the ECU. If you do need to offset it slightly and make new holes, don't drill them. Rather, use a sharp awl and a hammer to make the hole. This will push the metal in and give you more thread grabbing metal for your screws. You see people talk about dielectric grease a lot. Almost a buzzword of auto forums. Dielectric means insulating. So, normal grease could be somewhat conductive. This is why you put dielectric grease on your spark plug wires. You want to eliminate corrosion but not let spark conduct past your boots/insulators. So, in this instance normal grease would be preferred since you want a conductive path from the ECU case to ground. When you say the ECU's have failed, has the potting material melted out of the back? I agree that you could be getting a temporary ground fix from installing the new one, through the grounding screws. The white ceramic resistor is in series with the coil in the Ignition RUN position only. In Start position, the resistor is bypassed to give a hotter spark while cranking these old Dodges. So, a bad resistor will give the symptoms of engine starting but immediately shutting down when the key is released back to RUN position. You can check resistor by jumpering it out. This wont hurt anything for a few minutes, but over time could overheat your coil. If it works with resistor jumpered, you have a bad resistor. I would also check for corrosion at the (I think??) two prong plug to the distributor. I have had trouble there. Some of these distributors had two of these plugs. If yours does, check both and be careful not to reverse them. It seems like they can be switched. I had a Ram pickup with weird starting issues. The wire harness lay on the top of the driver side inner fender. The protective cover was worn on the bottom from many miles. I recoated it all with a new layer of electrical tape and it was fine after that. After all these years and miles, you have to check everything to make sure it hasn't worn through or broken.



1992 Chevy G20, 110" wheelbase, Mark III conversion, L31/4L80e swap, Express wiring harness.
Re: B200 Issue
rider #666807 July 23rd 2014 2:17 pm
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I've gotten the grounds cleaned extremely well on the firewall and when I pull off the control module there seems to be no rust build up. Also I have replaced the ballost resistor so that shouldn't be and issue hopefully.

Re: B200 Issue
rider #666808 July 23rd 2014 2:46 pm
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I second Ram4Ever's question- are the modules actually dead? Have you taken them in to a shop and had them tested?

What symptoms does the van exhibit wen the modules "die"?


Windows- they're what make a van worth owning!

Moderated by  Astro, Ram4ever 

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