An interesting CDI Ignition Issue

NYSpeed Automotive
1

We just finished our portion of the diagnosis on an interesting issue.

The car is the Evo 8 we posted the 674 whp dyno from.

The issue is that below a certain temperature the car wouldn’t start on it’s CDI + COP ignition setup, but started fine on the stock ignition. Oddly, I could warm the car up on the stock ignition, then fire the car up on the COP ignition with the temperature just as cold outside.

After testing we found a few things.
At 45 F and the car at ambient temp. from not running for a while, the CDI + COP setup provided strong spark.
At about 42 F and the car at ambient temp. from not running for a while, the CDI + COP setup provided very weak spark.
Under 40 F and the car at ambient temp. from not running for a while, the CDI + COP setup provided no spark at all.

So we started scoping supply voltage at the CDI during cranking at various temperatures and found they were consistant so the battery was providing enough voltage even at 35 F.

Then we picked a day when it was cold enough that the CDI wasn’t firing and ran jumper cables to a running car to get excellent voltage to the Evo during the cranking test. Still no spark from the CDI.

So today it was just barely warm enough that the CDI did provide spark. We double bagged the CDI box and stuck it in the freezer for an hour, took it out and plugged it in, no spark and the LED on the box didn’t even light up at key on.

We warmed the CDI box up by itself to 70 F, leaving the rest of the car cold and the car has real strong spark.

I was definitely expecting this to be a voltage issue where the colder the car got the battery just didn’t have the CCA to get everything going, but it’s really a temperature issue. The box is going back to the manufacturer in Australia for inspection and testing. They feel an internal component may be damaged, making it affected more than usual by the cold. We shall see.

BTW…for a few days I was warming the car up on the stock ignition, then swapping to the CDI setup. Once the engine bay was warm it worked fine LOL.

2

thats pretty crazy and cool at the same time.

I ran into a thing last week where my fuel pump relay would have a delayed kick over… approx 30 seconds from when i turned the key on… That was weird. Only happens below freezing.

3

Nice find…

4

Is this Autronic gear Mike?

5

Sounds like a bad solder joint inside the box to me.

Seen this before in some of the aerospace electronics I used to work on; when things got either warm or cold a bad solder joint would separate and cause issues. Probably all that is wrong. Complete PAIN IN THE ASS to figure out though.

6

It’s an M&W box.

Someone else did mention a bad solder joint inside the CDI box would behave this way.

7

that’s the kind of shit that drives techs up a wall tearing their hair out… i had a week of driving one car with a scan tool, and 3 multimeters temp. hardwired in chasing a sporadic short that would leave the car dead, and 3 other long term new launch vehicles with software update issues that almost made me quit and go work at McDonalds…

is this cdi box one of those poured full of goop so you can’t inspect anything?

8

I too would suspect a bad solder joint or a component with a poor internal bond wire connection, crack etc.

These type of “soft” failures always suck to find. Good work.

9

Finding this type of issue suddenly becomes fun when you figure it out without a huge PITA. Of course that’s not always the case. :slight_smile:

10

it’s a rush when you do find it but it’s a battle sometimes. the car i had the wiring disaster in was a cracked terminal that would get hot and open up but only once every 3 or 4 days… but the consolation prize is that it was an Imola yellow Audi S4 V8 6spd i got to rock for over a week on the company’s gas card.