Charging System Gremlins 86 2.9

[Mechman98]

Looking to get some of your opinions on some electrical issues with my 86.

Thus far I have traced it down to the charging circuit I think - if the alternator is connected (Y/W - B/O - LG-R wires) near the master engine misses consistently at idle (hot and cold, worse when cold) and stumbles to death (won't rev over 1200-1500 rpms) with the tach bouncing on every miss. Engine misses even worse with headlights or heater on. Unplug it - runs like a top no misses, plently of power until voltage drops from the battery not charging and the truck dies.

Alternator is new and wiring seems to be ok from the alternator to the connector, and then into the cab. Got continuity from the connector to the instrument panel connector for the ammeter, checked black/Orange to the fuse panel, and yellow to fuse panel and ignition. Dash lights seem ok brightness wise. Ran another ground from the battery to the dash ground under the column but haven't noticed any improvement.

Not sure where to look next. Replaced headlight switch with a good spare, multifunction and wiper switch. Ignition was not replaced, connector is clean and tight. Wiggle tested (coneector and key) with no issue as far as I can tell. I have the wiring diagrams and have been trying to go through it connection by connection without much luck

Any ideas are appreciated - Thanks

 

[MJ'sBlkBII]

Does the '86 have a seperate voltage regulator from the alternator? My '90 has a second plug on the underside (as mounted). Make sure it is connected and wiring is good if this applies to yours?

 

[Mechman98]

MJ - Thanks for the reply. No the regulator is internal and I did check the wire and both connectors for looseness, corrosion, etc. I'm pretty sure the issue lies after the plug by the master - possibly between the connetor and fuze panel. There is no apparent damage to the harness or connectors containing the B/O and Y/W wires

 

[MJ'sBlkBII]

What about where voltage leads to spark (e.g. solenoid on fender, ignition coil, or Tfi). I can't remember if these get current from alt., but I believe they do. Check fuse/relay in power dist. box? Might also get alt. tested for flat spot. Is belt adjusted proper? Just a few more ideas. If you meter the battery does it show the same jumping as the motor?

 

[Mechman98]

All solenoid connections were cleaned and reinstalled. Relays were replaced and the wiring seems ok - cranks and starts with no hesitation when relays - pcm are given power. Had an issues a while back with the coil connector, so I wired the coil directly to the harness (Accel Super Coil) so I don't think the issue lies there. Belt is brand new, not loose, installed with the new alternator this week. This is the third alternator (Original, Known good spare, and new for verification) all produced the stumble so I think its safe to rule out

Voltage was constant as far as I can tell while the engine was stumbling. Voltage did increase to about 14 v off idle as expected. There may be slight fluctuations but it may be difficult to see the needle move (no bouncing like the tach)

Thanks for the ideas. This is probably something stupid like a screw under the dash cutting through the wire jacket and grounding out. Need to check into it in a little more detail.