'85 720 Electrical Gremlin

[dayid]

Driving my '85 a few times now I've had where electricity (to the motor) has disappeared for less than 1 second. If the clutch is out you can feel a sudden shutter (presumably as the spark plugs don't fire so the engine misses?) and the voltometer drops to 0 and the battery/charging light comes on - but only for a heartbeat of time. I can also hear a short click (presumably a relay?) from the passenger side.. I'm thinking it's just the relay that's right under the passenger tray in front of the door hinges clicking as it loses power (that I'm hearing, not that it is the cause).

I had electrical issues with the main fusible link back almost a year ago, and since that part is no longer manufactured I replace the 5 lines there with inline fuses and bigger wiring than had been there before and hadn't seemed to have had any problems since (10,000 miles since). New alternator around the same time. About a month ago my voltometer was always showing my battery around 12V and after checking it with multimeter and charging it/checking it again it was bad so I have a 1-month old Optima red-top in there now.

Last night it did this to me twice - only these times "dying" for maybe 1-2 seconds before firing back up. It's done this sitting @ a light with the clutch in, at 60, at 70, with and without the A/C and/or heater running, with or without the headlights running, doens't happen when I hit bumps specifically like something is being banged around and shorting... so you can see why it's hard to track down. Also doesn't seem to care about whether it's raining or not or any other individual thing I can figure. When it does do this my headlights and interior dashlights all stay on too. I've poked around, all my fuses are good and tight, all my wiring seemss good and tight. I've also poked around at my key in the ignition to see if maybe it was breaking contact but it seems to be solid and good also.

Any suggestions on where to start? I'm still driving this daily 60-70 miles and it seems to maybe do it once or twice per week, but with last night doing it twice I'm afraid it's going to start increasing.

Another note: When it doesn't just hiccup but dies for 1-2 seconds, the seatbelt light comes on also, but once it re-fires that goes out. That's what had me looking at the ignition module. I was mostly just crossing my fingers and hoping maybe someone else magically recognized this issue and had encountered it similarly before.

[PEZi]

I know this is a simple, and possibly stupid answer.... but please first check all of your grounds. Make sure they are clean, and have good connections.

[woodbutcher5691]

^^^ Yea, what he said.

[dayid]

I know this is a simple, and possibly stupid answer.... but please first check all of your grounds. Make sure they are clean, and have good connections.

Yep, this is what others had suggested also. I verified each (some were a PITA to access). Disconnected each and sanded to make sure that I have a clean connection.

I also did the "big three" wiring for new alternator->battery and new battery->ground and engine->ground with some 8 gauge wire. I know many suggest going to a larger cable, but I believe that 8 should be sufficient for the distances I needed to cover (each under 18").

After studying the FSM wiring schematic, and the fact that the seatbelt light comes on, I keep thinking more and more that this is ignition based. If it were alternator, then the battery should carry the load for that brief moment. If it were battery, then the alternator should either stay lit or carry the load for that brief moment. In either case, the fact that I'm losing 100% power to the ignition (and thus that relay, the voltometer, and the charging system light) it really does act as if I suddenly had turned the key to ACC rather than ON.

I've briefly poked through the FSM tonight about this, is there a nice simple way to still use my key to call the ignition, but to jumper/hotwire briefly the ignition so that I can eliminate that as a cause?

[dayid]

I don't know why I hadn't tried this yet (well, yes, I do - it's because I don't normally think to cut off my vehicle while I'm driving at speed), but I'm fairly certain it's in the ignition system now. While driving along on an empty stretch I cut the key back to ACC, and sure enough - it felt/acted exactly how it does when it does this seemingly randomly. So I'll have to figure out a way to jumper around and figure out exactly what portion is dead so I can replace it.

[woodbutcher5691]

Sounds like the ignition switch is crapping out, but that is just throwing a dart.
I had all kinds of hell finding my gremlin. Came to find out the wiper motor was pulling my battery down.

[dayid]

Well, since I could definitely hear the Auto-Choke-Relay clicking over when this occurred, I went ahead and replaced it - since I am unsure if that is a cause or an effect.

I also eliminated the ignition and wired in two switches and a button (one switch for accessory power, the next for ignition, and then the button for starter).

I've checked and double-checked all grounds, and then driving home after swapping in the auto-choke-relay, this darn thing occurred again

The wiring diagram for this (FSM, EL-28) makes it look so simple, so this is quite frustrating.

Any other guesses or techniques to hunt this down?

[dayid]

So last night driving home from my midnight shift it died... and completely died - not jerk as it died and then lurched back to life again. Since I'd not been sure if it was the ignition switch or not, I looked down at my new lit-ignition switch - no light. So I check fuses, etc, and find everything good. Unfortunately (and fortunately) my main fusible link had burnt up before I got the truck, so I have all individual inline fuses there instead of the normal fusible link. It's made debugging some things easier, and others a little more PITA. After checking the fuses, got back in the cab and it was happy again.

In re-checking the splicing this morning the white/black-striped wire on the ignition-switch PAS connector (that takes a 15amp fuse on the fusible link to ignition) looks like of the X# strands of wire in it, only maybe 75% were clamped well by the connector at the ignition plug end. Removed this post of the connector and re-spliced it and re-inserted. AFAIK that end of the connector is 100% stock, and until trying to debug this the only time any portion of the dash was out was when I replaced the speedometer cable back 5 months and 5,000 miles ago. Even then, I only had the gauge cluster out, not the steering column/area where the ignition switch is, so who knows. I had since wired in the two switches and push button start - but that was many miles after this had originally occurred, so while I may have worsened it then, I couldn't've originally caused it.

I've only driven maybe 50 or so miles since redoing that end of the connector, but sometimes this problem had slept for 50-100 miles before re-popping up, so I'll just have to drive more to see.

I think this is where I really need to write myself better notes in the FSM, since "WL" wire being "White with black line" isn't very clear to me, and of all the tables/definitions/symbols they give in the electrical section, I haven't noticed any that describe the wiring colours/striping details.