EJ ignitor overheats - what happens?

[El_Freddo]

This little sucker on EJ wiring looms - the ignitor - does anyone know what happens to it when it overheats. Is it possible that it goes offline until it cools down again?

I'm asking as Toonga may have just highlighted why I had engine cutout issues when crawling through soft sand. Hoping to get to the bottom of this.

Cheers

Bennie

[Gannon]

The ones from EJ20G's have a heatsink on the back, but they control 4 coils

Mount a computer fan over it and see if it helps?

[El_Freddo]

Sorry, I should have been a bit more specific, this is from an EJ22.

The story goes that when did my conversion I was given a wiring loom with the ignitor and no bracket. I didn't care and I didn't think it was important for it to have a bracket so I just cable tied (classy) to the spare wheel mounting bracket in the L series. No issues there. I've since moved it to a small bracket near the brake booster. The next trip I went on the engine kept dying after meandering slowly through sand - it felt like it was running out of fuel and would have trouble firing up.

Usually it'd get going again after the bonnet was up for a bit and we "released" the pressure in the fuel line thinking it was vapourising. I think it was more about the time the bonnet was open for things to cool down (aka the ignitor) was more the fix to the issue.

I'll try out a heat sink and see what happens. I thought someone here might know more about the behaviour of this device when it gets too hot.

Cheers

Bennie

[Subydoug]

If I had to guess it would be an IGBT. Some have thermal shutoff so it would just shut down. If you look at a typical IGBT datasheet you can see that most of there characteristics are specified at a specific temperature (pretty much all electronic parts are) because they change with temperature. As long as you keep it below its maximum temp rating it should work fine. If its getting really hot, most likely something has failed inside the IGBT driver circuit and you should replace the ignitor module. I would at least make sure it has the same heatsink as stock if not better because that will be what was taken into consideration when it was designed.

Regards

Doug

[tambox]

Often incorrect wiring causes these things to get hot.
Check earth and power suppplies, then load leakage.
Would not surprise me if it had a internal thermal control system.
Geez points and simple on/off are good.

[TOONGA]

It is suprising just how little information is out there on the igniter / ingnitor.

section 2.7a Pages 40 -41 of the 1992 libertry FSM deal with diagnosing the unit but I've not found much else written about it.

Wikapedia has a page on the IGBT, it does a lot to explain how the igniter / ignitor works.

Every solid state transistor I have ever seen has a heat sink of some sort attached to it, and in the case of the Subaru item the back of the igniter /ignitor unit is an aluminium plate which is attached to a bracket, like the factory one below.



or the one I made for my vortex



As Doug stated it is more than likely that the unit has a thermal shut off in it to stop it from melting down. A rather expensive exercise from the prices I've seen for a new unit. (200 dollars +)

Bennie I would put the igniter / ingnitor on a heat sink as soon as possible.

TOONGA

[Gannon]

Given the age of the ignitor, I doubt it would be IGBT, more likely just power transistors. It simply takes care of the coil switching remote to the ECU to keep transients/back emf and electrical noise from damaging the ECU. From memory the ignitor also changes the polarity of the switching from negative to positive.

The ignitor on the EA82T was just a transistor. A guy on USMB found out the type and bought a replacement from radioshack. If you were dedicated you could make your own for the EJ22

[Subydoug]

I just guessed IGBT because thats what I would use. The one I put into my wagon was an IGBT. It had to be reasonably resilient because I cant suppressed the flyback voltages.

Try the heatsink Bennie, cant hurt anything.

Regards

Doug

[El_Freddo]

Bennie I would put the igniter / ingnitor on a heat sink as soon as possible.

Sure will. Just need to get these head gaskets sorted, I'll add it to the list...

I'll be keen to see what happens next time when out in that area.

Cheers

Bennie

[RSR 555]

The ignitor is there because the ECU will fry if it gets 12v from the coil. The ECU triggers the ignitor (via a negative signal) that in turn acts like a set of points. Like Gannon has mentioned, these are transistors and due to the 12v power that comes off the coil, the ignitor gets very hot and needs cooling down. This is done via the heat sink on the back of unit. From factory there is a white heat sink paste on the back of the ignitor. After many years of service this paste becomes old and looses it's cooling properties. I always use and recommend Silver Heat Sink Paste which is use on all CPUs inside every computer. This silver paste is available from most computer component resellers like Austin Computers, PLE, Vtech, etc.. even off fleabay.



The ignitor will do one of 2 things when it gets hot...

1. It will burn itself out and expand open and never work again.

2. Fail until it cools down again but do this too many times and it will fail completely. This also happens to Crank and Cam Angle Sensors.


I would highly recommend the unit be fitted to some sort of heat sink. Aluminium is one of the best metals to disperse heat but the little metal bracket that comes from factory works otherwise Subaru wouldn't have used it. Personally I'd do the same thing TOONGA has done.

[El_Freddo]

I'll have to dig up my pic of what I've done as a heat sink. It's also been moved over to the passenger's side so no extra heat off the cat converter...

Cheers

Bennie