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Discussion Starter · #1 ·
Hey folks,

I have a '84 Dodge with no spark. This truck is being used as a plow and is at camp (1hr away) so its kinda hard to get full details to you guys.

I checked the battery (12.6v) I get full cranking power, but no spark. I did tests on the coil, and even had a spare and swapped it (same thing). So I know its good. It had the wires,plugs, and even the distributor replaced by the previous owner. They must be good.

I was reading previous posts on this forum about the ECU? (bad ignition module?) I saw pictures of the module and located 2 of them on the truck. Both under the hood, one exactly above the steering shaft mounted on the firewall, and the other one on the passenger side (closer to the coil) The wires seem to go back to the coil.

I would like the test the ECU, how is this done. Also how much do they sell for if this is the culprit? Dealer item only? or generic part store.

Okay, thanks for any help.
 

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Discussion Starter · #4 ·
Hi,

Thanks for replying. I noticed there are 2 of those ignition control modules (both on the firewall). Is it possible to test these? Instead of replacing them? Also how would I check the pickup assembly? Its located under the cap, correct? Next to the starwheel? I'm not too familiar with electrical components.

Is that ballast resistor located on the firewall, connected to the coil? Thanks for any help. Electrical is not my cup of tea!
 

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the ballast resistor usually manifests itself as being bad by allowing the engine to fire when the starter is engaged and then the engine shuts off when the key is released to the run position
 

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Discussion Starter · #8 ·
Ok, I took a look at it briefly yesterday. I looked over all the wiring (its hard to follow, been butchered over the years). I checked for spark coming out the coil, no luck. I swapped the coil, same result. From knowing this, where should I look from here? The ballast resistor was also changed.

And can someone point me into a direction of a wiring schematic? Thanks.
 

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Discussion Starter · #9 ·
If I have voltage on the positive side of coil, what should it be around? 6-7volts? The ballast resistor cuts it down, correct? If there is voltage, then is my problem is on the trigger side of the coil? Pickup inside the distributor? Ignition module?
 

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Discussion Starter · #10 ·
Okay, I'm getting confused, haha. Whats the difference between the ignition module and electronic control module? I found pictures of both, one is almost next to the distributor, while the other one is right above the steering column. Some help would be greatly appreciated! I gotta get this truck out of the way!

The first picture is the electronic control module, and the second is the ignition module, correct?

Thanks in advance,
 

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Okay, I'm getting confused, haha. Whats the difference between the ignition module and electronic control module? I found pictures of both, one is almost next to the distributor, while the other one is right above the steering column. Some help would be greatly appreciated! I gotta get this truck out of the way!

The first picture is the electronic control module, and the second is the ignition module, correct?

Thanks in advance,
The unit in the photo you posted on the left, mounted on the center of the firewall, is your voltage regulator.

The Ignition module, electronic control module, ECM, ignitor, whatever you want to call it, is the thing in the other photo on the right, and it's usually mounted on the inside of the driver's side fender. This controls the ignition circuit.
 

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Discussion Starter · #12 ·
Okay, I checked out the truck today and here is what I can tell you:

With the KEY ON,

- I have power at the positive/negative, both within 1 volt of the battery
- I used a jumper wire from the negative post on the coil, and grounded it then removed the secondary wire from the distributor and checked for a spark. I did not 'see' a spark, but I received a nice jolt. So there is power.
- I used my test light, and checked the 2 wires that come out of the 'ECU' that plug into the distributor pickup. It did light up, but was very dim. ???

Okay, I should get pictures for you guys, but maybe tomorrow. Are there 2 ECU's on this truck? Because I see 2 units that are exactly the same (same plug in, same size) One is mounted right above the voltage regulator. There are 5 wires I believe. 2 wires go out to the coil/balast resistor, 2 go to the pickup coil under the distributor cap, and one green wire that is currently cut by the previous owner. The second unit is located low on the drivers side firewall. I think it has 5 wires, which go into the main wiring harness. Im guessing the one located near the distributor is the ECU, but what is the other one? I will get pictures soon, to try to help with this madness.

Any other checks that I should do? and what about that low voltage at the distributor pick-up?

Thanks
 

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Have you tried hot wiring it? Power to the coil and jump the ignition. That would bypass allot of crap and if it goes you have an idea where to look before or after the coil.
 

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Discussion Starter · #14 ·
Okay, I found a picture on another website of what it kinda looks likes. But, I'll try to hotwire it tomorrow and see what happens.

Can you take the ECU off and get it tested somewhere? I'm in Ontario, what parts store would be able to do it?
 

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Places like Auto Zone O Reillys Murrays Advance etc usually have a way to test them. But before you do try running a ground from the case (one of the mount screws) to a known good ground; a long wire with alligator clips makes a great temporary/test lead. If it starts then run a more permanent ground from that hold down screw to your known good ground.
 

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Discussion Starter · #16 ·
I have been using the ground screws on the ECU when doing my tests with my test light. The grounds are good on the unit itself. Thanks for the suggestion.
 

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Discussion Starter · #17 ·
Okay, as promised here are pictures. The first picture I attached: Can someone tell me what these two units are? I know one is the ECU, but which one? They are identical. The second picture is of one of the units which was located on the drivers side firewall. Its rusted pretty good, has some seperation on the back, and there is a slight hole on the front. I'm going to the junkyard tomorrow to get some ignition parts and try to figure this mess out.

I think I'm almost sure this is my problem, but some clarification on the name of the two units and how there work would be absolutely great.

Thanks again.
 

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Someone has been screwing around under there for sure/ I have NEVER seen a Dodge with 2 of those on there; I wonder if a previous owner wired in a 2nd one for some unkown reason (redundancy-as a "back up" maybe?) I had a weird problem with my 87 B van one time and come to find out someone before me wired in a heavy duty disconnect switch under the battery box (real hard to see) like you'd see on the bumper of a race car and put it in line with the battery negative cable; well it corroded up and I found it tracing wires. I put the other end of the neg back to the engine block and never another problem with it!
 

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Discussion Starter · #19 ·
I have some more pictures if it helps anyone with my situation. The wiring is pretty shoddy on this truck under the hood, due to the plow so there is extra wires running in every direction.





 

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Wow ..... I thought I'd seen the worst of the worst cluster f**ks before, but this one may be Numero Uno .... Don's right, there should be no reason for TWO ECU's and I've never seen one.
No WONDER you were confused as hell....

I've also NEVER seen an ECU or ballast resistor placement EVER up on the firewall over by where the voltage reg should be ... (On a truck, anyway) Yeah, that was obviously someones extreme HACK job at getting it to run, rather than fixing what was wrong. (And looking at the rusty/crusty ECU over by where it should/might be, it's no wonder it didn't run.)

I feel sorry for ya.... I've repaired some messes in my time, but nothing that looked like THAT .... :rolleyes: :rolleyes: :rolleyes:
 
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