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.

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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. .

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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.

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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.

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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
1993 Yamaha GTS1000
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1979 Yamaha G1A, rotary powered with Sachs KM24
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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!
1992 Toyota Celica AllTrac
1993 Yamaha GTS1000
1987 Mazda RX7 Sport
1979 Yamaha G1A, rotary powered with Sachs KM24
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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.
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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!

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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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