Igniter Repair for Cheapskates (2 Viewers)

[Lugal]

No other problems that I've seen with the GM module, other than the tendency for it to overheat after an hour or so of continuous driving. The worst was freeway driving to a friend's place in the Catskills. Fine all the way until I hit the slower mountain roads, then lots of coughing and spitting. I'll be driving up that way again on Labor Day weekend, so we'll see if it's any better now with the new heat sink.

 

[Spike Strip]

This may have been asked already, but did you use any heat sink thermal adhesive to attach the module, as well as the screws ?

 

[Spook50]

I'll bet the heatsink makes a big difference. Curious to hear if you have any more issues at all.

I wish I had easy access to a dyno so I could get actual numbers from different ignition setups. I've had no problems with my Mallory box, but I'm always looking for better (or a simpler way to get the same results).

Just came across this if you end up feeling froggy: http://www.summitracing.com/parts/dui-000222/overview/

 

[Lugal]

This may have been asked already, but did you use any heat sink thermal adhesive to attach the module, as well as the screws ?

I didn't use any on the screws, but in the first iteration I used plenty between the igniter and the top of the OE housing, and in the latest iteration I used it between the housing and the heat sink as well as between the heat sink and the igniter.

 

[Spook50]

@Lugal how did adding the heat sink help? Any further issues with the GM setup?

 

[g-man]

Lugal is last seen on 7/2017 so assuming he's no longer around. Anyone else done this mod and can verify some long term results? I am moving forward with the GM mod and have ordered the parts including a new heat sink.

 

[caladin]

It's a pretty standard mod in the old car space, as to long-term life, the GM igniter needs to be both connected to a good heatsink and use thermal grease or thermal glue to improve the connection, thermally.

if you don't properly manage the heat, plan to carry a spare and swap it when they die. They are cheap.

 

[simps80]

Proper heat management plus spares
It’s the answer for these old nla igniters

 

[g-man]

Got the GM module installed and it's running. Waiting for the heat sink to arrive and install before heading out for long road trip. Here are my Amazon purchases for this:

Amazon product ASIN B0054TQV14
Amazon product ASIN B07HDDWFDD
This silicone paste:
https://www.amazon.com/dp/B005VULWLA?psc=1&ref=ppx_yo2ov_dt_b_product_details

And this heat sink:
https://www.amazon.com/dp/B0012P2EQU?psc=1&ref=ppx_yo2ov_dt_b_product_details

 

[g-man]

I'll wedge the new heat sink between the toyota one and the module. I used stainless steel 8/32 x 1 inch round head machine screws with washer and cut washer and nut. Ill have plenty of room on the screws to include the thickness of the new heat sink but 1 inch does not come near the coil. Be careful not get to crazy tightening these. specs on my module was 8-12 INCH lbs. so pinky finger tight. I may double up on my nuts or use a lock nut later so that I don't need to worry about them vibrating loose. Very little room to turn the nuts (edit: they come very close to the side walls of the toyota heat sink) although I did tighten them down by hand and get an open wrench on them while snugging with a screwdriver from the top. Make sure to space out your holes evenly...just a little off to one side and you're going to have a hard time getting room for the nut and may end up putting the screw in from the the bottom and the nut on top.

 

[g-man]

One other thing I'll say that may be obvious. I removed the stickers from the heat sink and sanded the top before putting everything together.

 

[OSS]

I’ll bet that heat sink heats up the igniter transistors more than it cools them. The air temperature inside the engine compartment is insanely hot.
The Toyota aluminum igniter case has minimal grooves in it.

 

[g-man]

New heat sink on. 1 inch screws are now a bit short...had to remove the flat washers. recommend the 1 1/4 inch length. Had to drill more holes in the new heat sink ...thought the holes in it would match the GM module holes but no.

 

[Spook50]

I’ll bet that heat sink heats up the igniter transistors more than it cools them. The air temperature inside the engine compartment is insanely hot.
The Toyota aluminum igniter case has minimal grooves in it.

Working with electronics, I can say that even as hot as the air inside the engine bay is, the igniter will still get far hotter without some degree of cooling and have a shorter lifespan. The heatsink at a minimum (with thermal compound) is recommended, though an ideal solution would be a thermally conductive mounting against sheet metal that's exposed to outside air, like the wheel well sheet metal. You then have more mass (total mass of the surrounding sheet metal) to draw heat from the igniter, and outside air in cooler conditions to make it even more effective.

As far as the factory igniter's housing, in the late 80s and even now, OEMs only designed the minimal amount of cooling to get a reasonable lifespan from electronics. Even Denso used a "this is effective enough" approach when finalizing thermal dissipation designs on an electronic product. Whether it's just heavy use or an eventual breakdown in the compound/potting used inside, it always ends up being heat that does these igniters in.

@simps80 I would recommend flipping your heatsink over so the fins are facing up. With the convection of the fins, the heat being generated will build up and render the heatsink useless if the fins are pointing down. You need to give the heat an avenue to escape upwards.

 

[simps80]

Good tip will do

 

[g-man]

The small wires coming off the ends of the resistor were very flexible so I wrapped them about 3 or 4 times around the strands of the 18g wire then soldered them. Next I added heat shrink over each solder. Then one longer piece of heat shrink over the resistor and both soldered connections and their heat shrink. Finally I braced the entire section by wrapping electrical tape around a 2 inch long aluminum buck rivet, the resistor and soldered wires. This to minimize any flex that might break the tiny wires or the soldered connection. I was looking for something hard plastic and non conductive but I think the non ferrous aluminum piece should do fine.

Using self tapping sheet metal screws or just tapping some threads in the aluminum and using screws to secure the ignition module may be a better alternative. Easier to switch out with a spare if you're broke down on the side of the road. Also adding inline connectors to the yellow line between the dizzy and the resistor will help with a quick change out. Then when you build your spare add the right male or female connector upstream from the resistor.

 

[g-man]

5 hour drive trip to Hatteras and it held up great. 5 hours back a week later still no issues.

 

[mrmanos]

My mechanic just installed a gm part on top of the coil igniter, similar to the one in the photo earlier in this thread. I was worried about the heat build up I read about here. He told me that it’s not going to be a problem here, at 7,500’, high in the Colorado mountains. Like right now, it’s sunny and clear, and about 35 degrees. I never drive my rig outside of the valley I live in, and never longer than about 45 minutes max, just to town and back, 14 miles each way. I guess I’ll find out next summer when it’s warmer. But to the point of the thread: the gm work around part works fine. Mechanic said he looked around on the web, found a Toyota repair site(?), called me and said the only oem part was used, and $300 or more. It’s tire changing season here and he had a lot of other, more urgent work. Also he had to order diodes from somewhere, which took like 3 weeks to get here. Long story short is I am glad to have the old rig running. Only weird thing was it was idling way too high, but I know how to adjust idle speed. Unfortunately for me, I don’t know much about electrical stuff.

 

[Michael Hanson]

What about a small computer fan blowing on it?

 

[mrmanos]

What about a small computer fan blowing on it?

It was 25 degrees this morning here, and it is getting colder. It’s running great, and my longest trips are 15 miles into town, and 15 miles back. I’m not worried about heat buildup under the hood yet. If I drove longer distances it might be a problem, but considering where I live, I’m not worried yet.