Fix electrical gremlins

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Fix electrical gremlins

Postby ___Scott___ » Tue Jun 29, 2021 2:22 am

Long story short, I've been chasing an intermittent electrical issue for years. My latest effort was to clean all the contacts related to the ignition system. I used this stuff, DeoxIT D5:

Image

Now my car starts quicker and runs better. It's worth a try if you're fighting electrical gremlins.

It's too soon to know if it helped the intermittent issue though.
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Last edited by ___Scott___ on Fri Jul 02, 2021 3:57 am, edited 2 times in total.
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Re: Fix electrical gremlins

Postby 93celicaconv » Tue Jun 29, 2021 10:20 am

Whatever "this stuff" is, there is no image to open to see in your post (for me at least).

The update with the image is there now - thanks for the image. Looks like some good stuff to have around.
Last edited by 93celicaconv on Tue Jun 29, 2021 4:05 pm, edited 1 time in total.
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Re: Fix electrical gremlins

Postby grip-addict » Tue Jun 29, 2021 3:39 pm

Which set of contacts did you clean / do you think fixed it ?
Happy to hear that prelim tests are good!
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Re: Fix electrical gremlins

Postby ___Scott___ » Tue Jun 29, 2021 7:06 pm

I started by cleaning the easy to access ones, the EFI fuse and relay, the AFM connector and others in that area that were easy to get to. The connector on the coil, the ECU connectors, the igniter connector. Doing those generally made the car run better but didn't cure the intermittent issue which was that it sometimes didn't want to start. It would crank fine but not fire. The tach would sit motionless while cranking so I assume no spark.

The last connector I cleaned was the one on the side of the distributor. The connector was oily so I pulled the distributor and cleaned the contacts on both sides of the connection with brake cleaner and compressed air a couple of times, then hit the contacts with a bit of contact cleaner. After that it fired right up, much quicker (less cranking) than before. I replaced the o-ring on the distributor in hopes that the connector stays clean.

The starting problem mostly occurs after it has been sitting for a while so I'm leaving it alone until Friday then I'll try it again.
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Re: Fix electrical gremlins

Postby 93celicaconv » Tue Jun 29, 2021 7:26 pm

Can we assume, by the image next to your name, that you have an ST165?

When the tach is motionless when starting, that is telling you the tach is not receiving its input from the igniter. Since the engine position information comes from the distributor and is fed into the ECU, it is possible your distributor was not connected well to the ECU via that connection you worked hard to clean, so that connection is a possibility. So would the connector to the igniter. If the coil was faulty by itself (which often is affected by engine heat), the tach should have fluttered while attempting to start.

That's not to say there aren't multiple items at play here that affect ignition. Your coil resistance may be high when the engine compartment is very warm/hot. Your ECU could have some capacitor issues that are at play also. But hopefully it really was as simple as a wiring connector not tightly connected.

Leaving what you have alone for awhile now, but watching it closely, would be a good step. If no starting problems surface after several weeks, you likely got the, or the most significant, cause.
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Re: Fix electrical gremlins

Postby ___Scott___ » Tue Jun 29, 2021 9:55 pm

Yes, ST165.

Over the years I've replaced the coil and igniter (both new), and distributor (used off eBay). The coil and igniter helped it to run a little better but didn't solve the issue. Replacing the distributor did get it running once when it was stubborn about not starting but I didn't clean the connector contacts at the time.

I have a spare ECU that I've swapped in when having trouble starting but that never helps. When it starts, both ECUs work the same.

The point of the thread is that the DeoxIT D5 contact cleaner actually works. It's nice to discover products that work so I try to share a discovery when I find one.
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Re: Fix electrical gremlins

Postby 93celicaconv » Tue Jun 29, 2021 11:12 pm

And regarding your primary reason for starting this thread, that does look like a very interesting and fitting product - appreciate you sharing this item with the forum members.
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Re: Fix electrical gremlins

Postby grip-addict » Fri Jul 02, 2021 2:51 am

You get a chance to put more miles on it, is this still sorted?
Clearly I'm just shooting in the dark since I haven't seen your car, but I wouldn't be surprised if it was the distributor contacts/plug. That internal seal on the dizzy tends to leak and fill the cap (and in my case, also a bit of the plug) with a ridiculous amount of oil. Not great for electrical contact... Especially on a weaker signal like our factory VR sensors. Sucks too since they're such important signals...
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Re: Fix electrical gremlins

Postby ___Scott___ » Fri Jul 02, 2021 4:05 am

I was planning to wait another day to give it a try but I had to run into the office today (I normally work from home.) It fired right up. No problems yet.

That's encouraging but this has been a years-long battle. Only time will tell. It's gone more than a year before without trouble and then out of the blue just won't start. Then for no apparent reason will start. It's been tough to track down. The oily distributor connector is the closest thing I've found to a "smoking gun."
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Re: Fix electrical gremlins

Postby sefiroxx » Fri Jul 23, 2021 2:04 am

If you had to use deoxit, then that means your seals on the wire harness pigtails are giving out. Be prepared for a harness rebuild.

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