amps on ground circuit?

Odd question but I can't get my head around something....  A couple weeks ago a customer fried his standalone engine managment due to bad grounds.  The engine was grounding out through the smallerguage ground for the ECU.  I would like to prevent his from happening again.  Is there an amp load on the ground side of things?  I would realy like to see a breaker on the ground so that if it does start loadign up the breaker pops.  Or fuse.  Either case.  But I am not sure how to rate this. 

Would the amp load be on the power side of the load, or also on the ground side? 

Any fusing should be done on the power wire side, not the ground.  As stated above, whatever current goes in, has to travel down the ground wire to complete the cycle.  I have seen way too many times a 4 Ga power wire and an 8 Ga ground wire.  You need to have a ground wire that is the same size as the power wire. 

His fried brain will probably be a very simple repair.  He probably has a burnt trace or bad connection on the smaller ground wire.  Inside the box of course.

Primary fusing is done on the power side.  I was simply thinkng a backup might be nice in this situation.  What happened was unintential and not how it usally goes. 

Car in question is an 83 Volkswagen Rabbit GTI.  He had done an engine swap and painted everything up nice.  Unfortunatly he painted it all too wel..l.  The OE grounds on these are questionable to begin with after 25 pluss years, and I probally end up having to replace them in 3 out of 4 installs.  His tested okay though.  Turns out they wern't and were actualy grounding through my new engine managment harness. 

Engine managment in question is a MegaSquirt V2.2.  These are almost bulletproof.  Usally I have an easy time diagnosing damaged units.  This one kicked something hard inside though and I have not been able to find the failed component. 

As for the harness, he compleatly smoked the ground wire.  Fortunatly I use aviation quality wire for most of the harness.  I usally grab cheaper wire locally for the bigger power and ground feed wires.  SO other than having to open the harness up, remove burned ground, and recover, the harness was okay.  I had envisioned this remote possibility happening before, but of course it never had.