Hello I have a 86 2.8 fuel injection.I am having problems with my electrical. I just tested most of the wires, At the battery I am getting about 12.80v, and most every where else it is under 12, more around 11.50 and below. I have replaced the engine, injectors, alt, 2 battery's and about 3 or 4 starters,people told me that is was a grounding problem. I don't that think they know that much about cars. But anyway I must have a short somewhere.since i put the new engine in, when i would turn off the engine one of my dash light s would do this slow dying buzz sound. It's like i have to buy a new battery to even crank it for 2 days use.when the battery gets low i would have to be jumped off, once this happens it seems like my injectors are not getting enough juice,and the car wants to stall out.
SO IF ANY ONE HAS ANY IDEA'S, HELP ME OUT!! THANKS

 

Is that 12.8v at the battery while running ? If it is, I would be suspicious of the alternator failing. It should be in the 14.2±.2v area.
Also, don't overlook bad connections/cables. Make certain you have good battery to engine & chassis ground, it's just as important as the positive cable having a good connection. If your still running the original cables, you might want to consider an upgrade. I always like to use 8ga wire or bettter for a battery to chassis ground and a HD ground strap for the block to chassis ground to be be on the safe side.