Where can I buy new capacitors for my ecm?

To make sure you get good quality ones go to digikey.com
and order them. Seems to me it was the Tantalum capacitors that were high quality, but
it's been several years since I built the MegaSquirt EFI so I could be wrong

Wild

There are a lot of specialized electronics places that you can get them from.

Allied Electrical
Newark
Digikey
etc...

If you do a google search for the sizes it'll come up. Enter "100uf 25v" and you'll get an assortment of places. you want "Aluminum Electrolytic" ...Stay away from the Rubycon brand if you can ...and it should cost more to ship them then the part costs. Good quality caps are like 50 cents a piece maybe a bit more if you buy just one...

Here's an example:

http://www.newark.com/panasonic/eca1ehg101/capacitor-alum-elec-100%C2%B5f-25vdc/dp/96K9155


-Eric

Where can I buy new capacitors for my ecm? 

 
First consider if you have the soldering skills to work an a nearly irreplaceable ECM.  My colleague and component engineer recommends ONLY Nichicon and United Chemi-con. (We use million$ per year).  He also advises to AVOID Rubycon, at all costs (we've had expensive problems).  Why risk it, when known quality parts are readily available?  Tantalum caps, despite their typically lower ESR (Equivalent Series Resistance), aren't the best choice here.  Stick with the originally designed-in aluminum electrolytic style.  Don't forget to re-apply the conformal coating after rework.

The philips-head screws that hold the ECM in place are secured with threadlocker, making them a b*tch to remove.  But you can remove the battery and use a heat gun on the nut on the firewall to soften the threadlocker, making it possible to get them out.

On the west coast Mouser is a good source. Also Digi-Key, especially for the central and east coast. Make sure you get at least 105C-rated caps.  This is not a place to skimp on quality. That's why you're having to replace them now!  2000-hour rated caps used to be the standard, but 125C/5000-hr rated are becoming more common and avaliable, as the automotive industry uses more and more under-hood electronics.  I wouldn't think that ripple current rating is a critical parameter in this appication. Still, don't skimp on quality caps.   

Edit: The definitive cap-replacment article, now at: http://www2.izook.com/?page_id=231 (but the pictures at steps 7, 12 & 13 are FUBAR) Edit: There's a good copy of the original article at: http://www.billjohn.com/articles/others/ecm/ecmfix.htm

There are 4 values: 10uF, 22uF, 47uF, 100uF.  Choose a voltage rating that's at least 2x higher than the Zuk's 12V. 35V wouldn't be too much (some choose 50V, but I'm not convinced that it's necessary). Try to get the same physical size (diameter) to make replacment easier, but do not choose a smaller diameter.  A bit taller might be OK if you have enough height clearance. 
Note: All the years seem to have had a poor capacitor quality choice.  Older Zuks are more trouble-prone simply because of age.

That would be 105* C caps, is what Merlin is referring to, also the higher the
voltage rating the better suited to voltage spikes and breakdown of the insulation
in the capacitor it's self

Wild

Is there a specific year or years that had bad caps..I have a 94 should I go ahead and replace them before I have any problems..Thanks Dan

There are some small caps and some larger caps, should they all be replaced.

If you do a google search for the sizes it'll come up. Enter "100uf 25v" and you'll get an assortment of places. you want "Aluminum Electrolytic" ...Stay away from the Rubycon brand if you can ...and it should cost more to ship them then the part costs. Good quality caps are like 50 cents a piece maybe a bit more if you buy just one...
-Eric

You need to ensure that you get caps with a service life of 5000 hrs or better, with a temperature rating of 105C and a ripple current rating of 500mA or better. The voltage ratings must be at least that of the cap being replaced, there are a lot of inductive loads that generate much higher voltages than the nominal battery voltage. Capacitor choice is a compromise, the best caps have a service life of 5000hrs and most older Zuks will be well past that by now. There are no other capcitor types that can give the same performance, Tantalum capacitors aren't suitable due to their higher ESR ratings.
You need to follow ESD handling procedures when working on an ECU or you may find that later you will have ICs failing and some of those are custom and not available.