What's involved in rebuiding the F/I Control Unit?

[Alfred1]

I was just browsing Pelican's online catalog and came across these rebuilt ECUs and was wondering how they are rebuilt. Are there any moving parts in them? Is it just a matter of testing the individual components and replacing the faulty ones? How long do the original ECUs usually last?

[lapuwali]

No moving parts. All of the oldest Bosch ECUs (D-Jet and L-Jet) are all-analog electroncs. Any rebuilding involved would be checking the device and replacing any components that have failed over the years. Most of the parts are nothing more than plain resistors, capacitors, diodes, and discrete transistors. They'll generally only fail if abused, and theoretically should last forever. In practice, you'll eventually get some damage from heat cycling and vibration. Repair can be as simple as remelting the solder, or bridging a trace that's cracked from board flex.

[jamcleod]

probably would be much easier to either buy a rebuilt or a used ECU since you would have to match all the characteristics of all the components to the original specs which might require you to remove each component and test it. seeing as how there are probably 50 transistors, it would get tedious.... then if you made an error.....

[pbanders]

I spoke to the people at Bret Instruments about this, they rebuild ECU's. It's a pretty straightforward process. The unit is opened, cleaned, and failed components are replaced - standard electronic diagnostic techniques. Not all ECU's are rebuildable, many have water damage, case rust, etc. Additionally, some of the parts are hard to come by, so the rebuilder will strip them from junk ECU's and use them on ones they can rebuild (e.g. the germanium power transistors used in the injector driver stage).

Once you know what the expected waveforms are at each circuit stage, it's not too hard to find the failed components.