ECU Leaky Capacitor Repair

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ECU Leaky Capacitor Repair

Postby FC Zach » Wed Aug 09, 2017 10:01 am

Years ago I removed the ECU (89661-2B290) from my '92 due to the CEL staying on. It was later that I found this due to a failed capacitor.

Image

At the time I never considered repairing this and bought a replacement ECU from a forum member. It didn't help that my ECU looked like it was run over by a tank. .

Image

It wasn't until I saw a FB post of someone in need of a replacement ECU (theirs was in the same condition) that I remembered mine and decided to pull it from the attic for repair. After some online searching and seeing that this is a common issue, naturally I assumed mine is a ticking time bomb so I figured it would be wise to have a back-up ready.

I pulled two capacitors, both were leaking electrolyte. One on both the top and bottom board.

Image

I cleaned the electrolyte from the boards and placed an order for the replacements. I found the capacitors on ebay for very little. Just search "10uf 50v capacitors" (if it's the same caps obviously), I got two ten packs for ~$2.

Image

Image

https://www.ebay.com/itm/10-x-10uF-50V-105C-Radial-Electrolytic-Capacitor-5x11mm-Q6Z3-/172837714937?_trksid=p2349526.m4383.l4275.c1#viTabs_0
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Last edited by FC Zach on Tue Jun 18, 2019 5:04 am, edited 2 times in total.
1992 Toyota Celica AllTrac
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Re: ECU Leaky Capacitor Repair

Postby diceman » Wed Aug 09, 2017 11:38 am

There is a good thread on GT4DC but unfortunately photobuckets sharing policy means only my pics remain.
http://www.gt4dc.co.uk/forum/viewtopic. ... =30#p57080
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Re: ECU Leaky Capacitor Repair

Postby FC Zach » Wed Aug 09, 2017 12:56 pm

diceman wrote:There is a good thread on GT4DC but unfortunately photobuckets sharing policy means only my pics remain.
http://www.gt4dc.co.uk/forum/viewtopic. ... =30#p57080


Good read, thanks for the extra material!
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Re: ECU Leaky Capacitor Repair

Postby underscore » Wed Aug 09, 2017 3:48 pm

Thanks for the reminder, I've been meaning to take apart my spare ECU and replace all of the caps in there (they're all going to be old and crusty by now).
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Re: ECU Leaky Capacitor Repair

Postby thetyrant » Sat May 04, 2019 11:36 am

Just pulled the Ecu out of my st185RC after having some intermittent cutting out while warming up as I re-commision from winter storage, initially I thought problem was EFI relay next to battery as it was clicking a lot, changed that and car seemed ok but once warmed up and stopped it wouldn't start again! gave a wiggle of the relay which seemed to allow it to start but now think that was pure luck, however took fuse box out to check wiring and clean all connectors on backside of it, there was a little corrosion on some terminals but nothing I would of thought an issue and all wiring was good, cleaned it all up and refitted everything but still cut out once warm!

So after knowing about the old cap failing issue Ive just taken the Ecu out and opened it up to find the same C810 capacitor as above has leaked and corroded the leg off!, will check for others as well and hopefully after replacing these problem is all sorted, fingers crossed as just fitted new tyres on ready for summer :D

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Re: ECU Leaky Capacitor Repair

Postby Numbchux » Mon May 06, 2019 4:55 pm

Excellent write-up on doing this on 1UZ ECUs. I'm in the process of 1UZ swapping my 4Runner, and did this a couple weeks ago (10 caps on my '94 SC400 ECU). Excellent information about replacement caps, beware the "cheap" ones (good ones aren't expensive, and DigiKey is a great source). Good solder and flux makes it a pretty easy job.

https://www.clublexus.com/forums/ls-1st ... citor.html



I need to get to the ECU/cruise unit to fix a cruise issue on my Celica, so I might pull the ECU out and replace those on it as well.
-Chux
'91 Celica GT vert, poly bushings, rear discs, etc., Summer DD
'87 unTurbo 4Runner, 1UZ swap, 35s
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Re: ECU Leaky Capacitor Repair

Postby lalojamesliz1 » Tue May 07, 2019 3:44 am

After seeing this a couple days ago I opened up both of the st205 ecu's I have to inspect them. One that I have been running in my all-trac and the other I just acquired with the gen3 swap I just bought. They both look in good shape inside luckily but I ordered all of the caps inside the ecu's (6 different ones) from digikey and now I'm considering getting a much better solder station like the one suggested on the Lexus forum.
I love in formative threads like this :D
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Re: ECU Leaky Capacitor Repair

Postby thetyrant » Tue May 07, 2019 5:58 am

Ok spent some more time going over my RC ecu and closer inspection of the Ecu found 3 blown caps and 1 just starting to leak, details and pics below.

Main Large PCB
C101 (100uf/10v) - totally gone one leg, no pcb damage
C810 (10uf/50v) - totally gone one leg, localised track damage wire need to bridge.

Small top PCB
C500 (100uf/50v) - very small leakage visible on one leg changing as precaution, no pcb damage
C512 (10uf/50v) to - one leg gone, minor track break to triangle pad solder bridge possible

Replacement caps ordered should be here tomorrow, got loads of spares of all values in ECU coming if anyone else in UK needs any free just cover postage get in touch:)

Pics of worst below, sorry bit blurry!

Image

Also the PCB damage pics below, ive marked on in Red where I need to repair breakage, in yellow is partial track damage from leak which I will add a wire repair across as well to make sure its tiptop.

Image
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Re: ECU Leaky Capacitor Repair

Postby Soup84 » Thu Mar 26, 2020 9:26 pm

Looks like I'm in the same boat.

Any new info on this project? I'm fairly experienced with soldering but not so much with soldering a CB. Any tips? Should I just send this off to get fixed?
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20200326_182703.jpg
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Re: ECU Leaky Capacitor Repair

Postby underscore » Thu Mar 26, 2020 10:52 pm

If you've got some dead electronic device sitting around pop that apart and use it to practice. If you have tweezers or small pliers snip off the old capacitor first so the old legs are easier to remove one at a time. Note the orientation first as they have polarity, if you can't tell for one just ask as I have a spare ECU and can easily snap pictures. Replace them all while you're in there. Go slow since it's easy enough to add more heat any try again, and don't try to force anything.

Each of my ECUs took about an hour total and that was puttering through it. I found it pretty easy since this older stuff has large components that are nice to work with. Granted I did take a soldering course in college where we got down to trace repairs and the fiddly surface mount stuff.
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Re: ECU Leaky Capacitor Repair

Postby Soup84 » Fri Mar 27, 2020 3:02 pm

underscore wrote:If you've got some dead electronic device sitting around pop that apart and use it to practice. If you have tweezers or small pliers snip off the old capacitor first so the old legs are easier to remove one at a time. Note the orientation first as they have polarity, if you can't tell for one just ask as I have a spare ECU and can easily snap pictures. Replace them all while you're in there. Go slow since it's easy enough to add more heat any try again, and don't try to force anything.

Each of my ECUs took about an hour total and that was puttering through it. I found it pretty easy since this older stuff has large components that are nice to work with. Granted I did take a soldering course in college where we got down to trace repairs and the fiddly surface mount stuff.



Thanks for the reply! That Lexus write up is pretty good too. Now to order caps... looks like i need three: 100uf 10V, 15uf 35V, and 10uf 50V, but there's so many options on Digikey!! AHH!!!
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Re: ECU Leaky Capacitor Repair

Postby Numbchux » Fri Mar 27, 2020 5:40 pm

Yea, I think my 1UZ board only took a few hours, and it was 10 capacitors on 2 boards (soldered ribbon cable between them, so carefully bend one out of the way), and 1 cap was almost inaccessible under the case of the ECU.

Flux, and desoldering braid made it so much easier.

I set up a soldering station on our dining room table (Thank Bob for my Wife putting up with me!!!), and plugged away. no big deal.
-Chux
'91 Celica GT vert, poly bushings, rear discs, etc., Summer DD
'87 unTurbo 4Runner, 1UZ swap, 35s
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Re: ECU Leaky Capacitor Repair

Postby underscore » Fri Mar 27, 2020 6:20 pm

Here's what I ordered from Digikey. The quantities are double what they should be since I was doing 2 ECUs. Double check the cap values as well just in case my RC is different from yours (I don't think it is, but just in case).

Image

I went with Panasonic purely because they're Japanese and I'd heard good things about them.
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Re: ECU Leaky Capacitor Repair

Postby FC Zach » Sat Mar 28, 2020 11:37 am

Soup84 wrote:Looks like I'm in the same boat.

Any new info on this project? I'm fairly experienced with soldering but not so much with soldering a CB. Any tips? Should I just send this off to get fixed?


My repair worked great and I'm still running on that ECU. . I even repaired my spare ECU just in case. It's not difficult as others have mentioned, just take your time and try to not overheat the board while desoldering. The mention of cutting the cap off to more easily remove the legs is a great tip. I would also recommend cleaning your iron tip and tinning it but if your proficient at soldering then that should be a given.

Numbchux wrote:Flux, and desoldering braid made it so much easier.


Great recommendation! Flux is a must to get the solder to flow. There are many desoldering methods/tools but my favorite is a vacuum pump type, I use an inexpensive manual version that can be had for five bucks off Amazon. . Looks like this:
619qEIC5iyL._SL1500_.jpg
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Re: ECU Leaky Capacitor Repair

Postby Soup84 » Mon Apr 06, 2020 10:36 pm

First off, thank you so much for the help!

Good news, bad news.... Good news, the repair went well, all caps were replaced and my car started right up.
Bad news, I'm still getting the same malfunction: an intermittent brake light that comes on with boost

Learning points from my experience:
1. Cleaning out the solder AFTER the cap is removed was easiest for me
2. Check the lead gap before ordering: I ordered two sets of one cap with different gaps and one worked easier than the other. You can still use caps with different spaced leads it just takes some adjusting
3. Adding a little solder to the existing soldering made it much easier to work with while removing the old caps.
Attachments
20200406_192256.jpg
Old cap
20200406_192329.jpg
Cap removed, pre-cleaned
20200406_192413.jpg
Gently cleaned with alcohol and a q-tip and replaced the cap
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1993 All-trac - Salvaged parts, RIP
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