Series 2 3800 ignition module and coils retrofit

[Oceandaemom]

I will start off by saying that this post is actually covering my ignition work done to my 1991 Lesabre, but I hope that it will still help some people since the 91 Lesabre uses the exact same 3800 LN3 (Pre Series 1) engine as a Reatta does. 

 

For the last month of me owning my Lesabre, it developed a stutter / random misfire at low RPM, which got worse as the engine / outside temp got hotter. Finally on Friday afternoon I was driving home from a job site and the car completely died on me. Testing with a spark tester and then a DVOM showed no spark from the coils, and no signal from the ignition module to the coils. After doing some research I realized that despite the ignition module from a Series 2 engine being physically different, and made by a different company, they are electrically the same.

 

There are a few benefits of using a Series 2 (Delco Built) ignition module / coil setup over the stock LN3 (Maganvox) built setup.

 

- You can get the entire module and three coil packs from a salvage yard for about $40 (opposed to the LN3 one which is not common in yards around here)

- The coil packs are individual which makes it easier and cheaper to repair in the future

- It is a lot more reliable then the old Magnavox unites

- It is more powerful, so you can increase the spark gap from .50 to .60.

 

Just to be clear, if you find yourself a Series 1 (1992-1995) ignition setup by delco it will bolt up directly to the mounting bracket of the LN3 and the fabrication of an adapter plate is not needed. The Series 1 engines are harder to find in salvage yards around here but the Series II ones are super common, and can be made to fit with the fabrication of a simple adapter plate

 

The original ICM of the LN3 bolts to what I will call the backing plate. On both the LN3 and Series 2 the backing plate is a chunk of cast aluminum that bolts to the front head of the engine and also to the alternator in the case of the LN3. They are not interchangeable between cars as the LN3 has three holes which the ICM attaches to with studs and nuts, and then the LN3 coil pack bolts to the top of the ICM. The Series 2 has six bolts which go through the coil packs (2 per pack), through the ICM, then into threaded holes in the backing plate.

 

The goal of the adapter plate I built was to on one side have three studs that fit in the LN3 backing plate, and on the other side have six threaded holes for the Series 2 ICM and coils to bolt to, simulating the backing plate of a Series 2 engine. 

 

In the picture below you can see I cut out a chunk of 1/8" aluminum plate to 9" x 17" It must be at least 1/8th thick or else there will not be enough room for threads in the holes. If I did it again I would also use steel instead of aluminum, but its what I had laying around. I used a press to press out the three studs from the LN3 module, used the holes where the studs used to be in the module to mark and drill holes in the aluminum. I then pressed the studs into the aluminum and used some JB Weld epoxy to enforce it (you don't want the ICM coming loose on the highway).

 

 

 

 

I then used the Series 2 ICM to mark the spots for the six holes, which I then drilled with a 5/32nd drillbit and tapped with a 5mm x .08 tap to fit the six bolts that came with the Series 2 ignition setup. In the picture below you can see the adapter plate attached to the ICM and coil packs.

 

 

 

I then just used the original nuts to bolt the adapter plate and ignition system down to the LN3's backing plate, and connected the ICM connector and tightened the 7mm bolt on it.

As you can see in the picture below, it looks clean and original to the car (good if you