The story so far goes like this:

I have a 90 Dodge Ram Club Cab with long bed. It has a 318 engine and it used to be EFI, but the previous owner modded it so now the truck only runs on LP gas. However, the good ol' computer still lived for the ignition system, but after 2 weeks that I bought the truck, the dang thing broke down when I was on my way to work. Took it to the electric shop and the guy determined the computer was bad and since I don't need the computer anymore, he suggested me to install a vintage electronic ignition system with the 5 pin ECU, the resistor and all that you're probably already familiar with.

I found everything here in ol' Mexico at a decent price, but I still had to hunt the appropriate distributor down. However, the guy who advised me of the EI system never told me how the distributor for this application exactly was. I looked over the internet and found out which one I needed, and found one at a local wreck yard.

I installed all the gear and the thing I realized is that the truck is very hard to start. I have to be constantly moving the distributor timing each time I want to start it and the truck usually needs a lot of batt power to crank up. Also, the battery I used was good until the moment of the failure, but I think that because afer being discharged by me trying to start it the day it failed and all these days without proper charging, it got damaged and then it was getting discharged by no reason and it never starts the truck, even if it's charged. I placed another battery and the truck started right away, even with a cold engine. I started the engine, then shut it off a couple of times and had no problems, but I noticed that the battery gradually got discharged. Next morning I tried to crank it before I went to school and it had decent juice, but not enough to make the engine spin. I recharged the battery then, and jumpstarted the truck. After 20 or 30 seconds of cranking the truck started, but the voltmeter goes down, till the truck eventually dies.

I got the alternator off the engine and took it to the electric shop. The guy there told me the alt is fine, and it's not charging because of the dead computer, which has a built in voltage regulator and it's not sending the signal to the alt so it can charge the battery. The good news is that he told me that a separate volt regulator can be installed to make it work.

The bad news is that I still can't fire up the engine easily after many hours I've spent trying to figure out what's the problem. I remembered that when the truck broke down the very first time, I replaced the coil and the guy at the auto parts store told me that the coil was for electronic ignition applications, and that it has a built-in resistor.

Because of that fact, I'm starting to think that because of that built-in resistor on the coil and the already-resisted positive signal I'm sending from the newly electronic ignition installation, the spark is too weak that it's not enough to fire up the engine. Also, when I try to start the engine I have to put the distributor on a very advanced position, then the truck starts all messed up and then I correct the timing and it runs great, but if I shut it down and try to restart it, it won't work. That's why I'm thinking the spark is weak.

What do you guys think? Am I right or wrong? Do you have any other suggestions?

 

What a cluster F---! You may have some incompatible components here. The 5 pin connector ECU (electronic control unit) was used with both a single pick-up distributor and a dual pick-up. It was also used with a single and a dual resistor. The dual resistor was used with a single pick-up only while the single resistor was used with single and dual pick-ups depending on year.

You must know what year your ECU fits to know what else it needs to make it run properly. You also need to tell us how many pick-ups are in the distributor and is it a single or dual resistor or no resistor at all. Do you have a starter relay or not because this will effect the proper wiring of the 5 pin connector?

A separate voltage regulator is needed with a good wiring diagram for the truck year that your ECU was used in. A coil that matches that year ECU is also needed.

 

Thanks for the reply, SEAL.

Well, I don't have a camera in handy so I'm not posting pictures, but I sure can tell you all the details, some of them which I omitted in the first time to make the story a little shorter.

The thing is like this: I went to the auto parts store and got a 5 pin ECU. Don't know the year or anything because the guy on the electric shop just told me to get a 5 pin ECU, a dual resistor, the wire harness and the distributor had to be hunted down.

I went to a local wreck yard and I got a dual pickup distributor that looked pretty much like a Lean Burn distributor, but it DOES have vacuum canister, weights and springs. I installed it and used only the male/female connector (the other one has 2 male prongs) because the other connector was all dirty and I assumed it was disconnected when it was working on its previous engine. The engine could start with some difficulty, but started.

Then, when I went to a different electric shop to service the alternator, explained the issue to the guy there and he sold me a single pickup distributor which is in the engine right now, and I'm experiencing the so mentioned problem with either of them 2 distributors.

I wired the ECU with the dual resistor as prescribed in allpar.com (i will post the link at the bottom of this message) but I didn't connect the wire from the starter relay because I don't know which one is it (HAHA you may think I'm a dumba$$ right now, but sorry, didn't think it was that important since the truck started).

Link to the diagram I followed for wiring ECU:

http://www.allpar.com/fix/electronic-ignition.html

As I mentioned on my last post, and thinking about what you just told me, SEAL, I think something around the coil or the wiring on the ECU is the issue. I really think the coil is the one to blame, because of that "built in" resistor, but I haven't had the chance to check with another coil

 

That first wiring diagram is correct for 74-79 models. That ECU goes with the dual ballast and the single pick-up distributor. Make sure the 5 ohm and 1.2 ohm are on the proper side. I think you may be OK once you change out the coil. I have been on this site for quite a while now and have only met 2 people I thought were dumb a$$es and others on here agreed, and you aren't one of them. LOL

Just for info; The starter relay is not used in this set up but is needed for 81 and later models to wire up the dual pick-up distributor.

 

Thanks for the valuable info, SEAL. My truck is a 90 but the setup I installed is for a 70's truck with single pickup dizzy. According to you, I shall not use the starter relay and I must replace the coil for a non-resisted one to make the truck work, right?

I'm sure about the resistor values because I tested it with a car light bulb because the resistor had no annotations about which side is which. And I understood that the side of the resistor with higher value was the one with the more faded light intensity.

I also thought that I could put 12V directly to the built-in resistor coil, coming from the ignition switch, just to test my hypotesis about this freaking problem. If everything goes right I should then replace the coil with the appropriate one. Do you think it'll be OK if I do this or should I get the coil before maki any tests?

 

You are correct on the light bulb brightness indicting resistance values.

If you look at the wiring diagram you can see that the coil gets a full 12 volts from the ignition switch contact #2 as long as the key is in the start position because it bypasses the resistor. To run correctly the system needs a slightly reduced power and that is the purpose of the ballast resistor. With an internal resistor coil in this system you are reducing power during the start phase and even more during the run phase. Without knowing what the internal resistance of your existing coil is it is hard to predict how it will react when you do different things to it. Testing it can't harm anything, it just may not help and drawing conclusions from from what it does may not be a prudent thing to do. At this point I would go ahead and just replace the coil and be done with it as they are not really that expensive.

 

Thanks again, SEAL. You don't know how much you've helped me and I really appreciate it. I posted this same issue on other forum on last Thursday, but I haven't received any answers yet, and you've answered and helped beyond my expectations in less than a day.

Let me tell you something:

Yesterday I read your post about me being OK with the coil after replacing it. Since I don't want to spend the money (the last I have until this Friday, when I get paid) for having the electric shop guy install the separate volt regulator, I did the test with the built-in resistor coil I told you about. I hooked 12V from one of the wires coming from the ignition key all the way directly to the coil. I jump started the truck with my dad's car and it started right away, no problems except for the low voltage caused by my almost-dead battery. For this reason (low voltage), the truck needs a little more cranking than usual, but if I let my dad's car charge my battery a little bit more, the truck starts fast and normally, which confirmed my hypothesis with your help.

I will get my neighbor's battery charger to juice up my batt, then I'm taking the truck to the electric shop guy to get the volt regulator so my truck can charge now. On Friday I will replace the coil to finish this dang problem once and for all, but I just have one silly question: You just said that when cranking, the coil gets 12V (according to the diagram), but on your last post you mentioned that the starter relay wire is not needed in this setup, so I'm kinda confused now. Should I put the starter relay wire or not?

I thank you very much for all the help provided, man. I will keep you updated on anything that happens on the next days.

Thanks again.

 

The starter relay is not used in this setup. Forget it.

First these 2 facts must be understood. In the start position power is available at both ignition switch terminals 1 & 2. In the run position power is only available at terminal 1 at the ignition switch.

Start at the coil positive terminal in the diagram (the pink wire) and trace where it gets its voltage. You see that it can draw power from two different terminals on the ignition switch depending on which terminal has power. In the start position, the full power that is available at terminal 2 over rides the power from terminal 1 (which is lower because it has to flow thru the resister). When you release the key the ignition switch automatically returns to the run position. In the run position the ignition switch terminal 2 is de-energized and has no power to give anymore. The coil in the run position must then accept the lower power that is available from the ballast resistor that is powered by the ignition switch terminal 1.

 

OK, understood and written-down.

I will look for the wire coming from the ignition switch that comes from the start position and hook it there, because I have no wire connected on the terminal that goes to the coil with the switch in the start position.

I'm sorry for the misunderstanding, I meant for "relay starter wire" the wire you just mentioned, the one that supplies 12v when the key is on start position. I didn't connect it because I didn't know the importance of it, and assumed something was wrong with the diagram.

Thanks for the help.