A Strange Sequence Of Events - Probable Electric Problems

I had just finished installing my newly-welded fuel tank and adding from a can enough gas to get to the gas station to fill up my tank, and I was on the way to a nearby gas station when I saw sparks fly from under the hood and everything shut off - lights, engine, everything, in the middle of the road.

I turned off the ignition and took out the key, and as I was pushing the truck to the side of the road, some of the lights on the dash were still on, the dash was humming with an annoying low beeping/buzzing sound, and I noticed an electrical burning smell (not overpowering, but enough to notice). It didn't stop buzzing until I started yanking at the negative battery cable in a feeble attempt to disconnect it without having any tools on me.

After sitting with it for a few moments, I tried to start it again, not really expecting anything, but it actually started back up. When I released the clutch, there was the sound of a whining belt for a moment before it started moving. I then went the rest of the way to the gas station and back without major incident.

For the rest of the ride, my headlights were notably dim and flickered consistently, and the turn signal lights on the dash were dimly illuminated in an unusual pulsating fashion. Halfway through the drive back, the 'check engine' light came on and stayed on. When I got back, I looked under the hood again and didn't see anything obviously visibly amiss.

I gather that something of an electrical nature obviously went wrong, but I'm not sure what, or where to go from here. I also gather that my v-belts might be loose, but I can't imagine what kind of correlation there would be between the belts and electrical problems.

An extra piece of information that may or may not be relevant is that the truck had been left sitting for about two weeks, and when I first started it, I had to turn it over two or three times before it would start. Perhaps a low battery level could have contributed in some way to whatever happened?

Any signs of 'arcing' on the hood? How secure was your battery and the hold-down clamp? It sounds like you had a direct short on the battery somewhere. This event is bad all over - for the battery and the alternator. A slipping belt "shouldn't" cause a fault like this but it will squeal like a pig if the alternator is suddenly overloaded (see it happen when guys install a big audio system and add a heap of accessories, then try to run the lot with a stock charging system - there is so much load the alternator it prevents it from turning with the belt, thus causing it to slip on the pulleys). Check your positive leads from the battery and the alternator for signs of burn out. Next check your main fusible links for damage or failure. The fault must be on an un-fused circuit or it would've blown something. If you can still get it to start, check your charging voltage with a multimeter. If it's showing anything less than 13.8 volts there's something amiss.

Thank you. The battery was not properly secured as it should have been. I think what happened was that I hit a bump in the road which caused the positive connector to hit the side of the engine bay and short out. The fuses seemed to be in order. The positive lead was a bit charred, but it didn't look so bad that it shouldn't conduct electricity.

When I turned it on the following day, the 'check engine' light was still on. I left it running long enough to charge the battery, and then checked to confirm that the battery was at full charge (it was). I disconnected the battery for a few minutes, cleaned the battery acid off of the negative battery terminal, and when I re-connected it and turned it back on, the check engine light was gone.

I drove it for a day or so with no problems, but then the 'check engine' light came back on and started to flicker. As I drove further, the radio started cutting out with the flickers, and then the engine started lurching.

I think that there's a bad connection somewhere on one of the battery cables. I visually examined them, and they all look fine except for the char marks on the positive connector. I'm going to clean the battery acid off of the positive terminal, try to cut a little bit off of the wire, replace the lug itself, and wrap it in electrical tape for insulation.

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When a positive battery lead goes bad it creates a load from resistance. My favourite home made concoction of citric acid powder solution does a great job of dissolving the sulphation on battery terminals and connections. Good, clean terminals go a long way to ensuring a healthy electrical connection and battery life. Add a coating of petroleum grease to protect the terminals and connections from moisture and air afterwards and it should solve your sulphation issue (your positive terminal needs a plastic connector shield over it in case the battery comes loose - it will prevent another accidental short circuit) :thumbup:

check your grounds too. Bad connections cause vehicles to act wierd

The truck will start up and drive fine, but the headlights flicker and are noticably dim. However, when I take my foot off the gas and press the brakes, the radio cuts off and the headlights get brighter, both for about half a second. If I drive it like that for longer than 10-20 minutes, then check engine light will come on.

I've replaced the charred positive battery cable lug, replaced all three fusible links (they weren't broken, but the 20v looked a bit corroded), cleaned the crud off of the battery terminals, and disconnected the negative battery cable at the engine to clear the crud off of it at that end.

The only thing that makes sense to me is that it could be the voltage regulator. After taking a look at the Hayne's manual, it looks like there are two kinds: one that attaches to the back of the alternator, and another that's on the inside of the alternator, and it doesn't specify which is for which years. I think that mine (for a 1995) is on the inside, which means that I'd be better off just replacing the whole alternator. Am I on the right track here?

Have you tested the output voltage on the alternator? And have you done it with just the engine running and then with the electrical system under load (lights, brakes on, radio etc). I have only 2 theories - a faulty regulator or a dead battery plate. I think you are heading down the right track and the fact that the alternator output jumps when it's under load suggests that there's a fault with the alternator. The check engine light is a hint at something else is afoot with the charging system. Shorting the electrics can also badly damage an ECU (some ECU's monitor the alternator and control it externally but I'm not sure if this applies to the MM)

Okay, now I'm completely baffled. It's not the alternator or the battery.

I temporarily put the battery from my Miata in the Mighty Max for troubleshooting, and it behaved in the exact same way.

I then took the alternator out and took it AutoZone in order to have a bench test run on it, and they told me that it was operating exactly as it should. I went ahead and bought a new (reman) alternator and installed it anyway, just to remove any doubts as to the accuracy of the test. Sure enough, it continues to cut out in the same way with the new alternator.

The cutouts can't be reproduced if the truck is not moving. If I run it with the electrical system under load, but without moving the vehicle, then nothing cuts out, regardless of how I rev the engine and press/release the gas/brakes. However, if I keep it under load, then when I start moving and then release the gas pedal, then everything cuts out much more dramatically than usual, and the engine sputters and sometimes stalls out completely.

Does that sound like it suggests the ECU as the problem? I'm all out of ideas. It previously seemed that the battery, alternator, and the fusible links on the positive battery post would have been the obvious culprits.

It could be - a bad short like that can cause all kinds of gremlins to appear. It could possibly be the TBS sensor out of adjustment or bad, but it doesn't explain the only under load part. Check the distributor cap, wires and coil - they are right next to where the short occurred and could have been damaged when the battery shorted out.

I still believe its a "ground issue"....using di-electric grease at ALL clean connections: verify quality cables (best to go new...cheap enough) are grounding battery to engine block, engine block to frame, engine block to cab (fire wall), cab to frame. Even though the truck starts the ground from the battery to the engine block may not be quality enough (& even if you have all of the above mentioned grounds in place it doesn't mean they are good enough due to grease, loose connections, poor wire end connections, frayed internal ground cables,)....also "if possible" try not to place multiple connections at a single point (positive or negative like your picture above).....hope this helps.:)

My truck acted weird also but not the same. Driving the truck it would turn off randomly as if I pulled the key from the ignition. I found my issue to be an intermittent open at the fusable links main wire terminal from the battery to the 3 circuits. I replaced the fusable links with a new fuse box I got from Amazon. Try to "wiggle" the fusable link box and the wires to it. One circuit should be the headlights, one for fuse box in the cab, and one for the engine/ecu. That's if your truck still has the fusable links. Lol

Those of you who suggested that this was a grounding issue were mostly correct. I took it to a local shop, where they installed new ground wires which didn't previously exist at all, particularly for engine bock to firewall and negative battery post to engine (corresponding to ragragtimetime's suggestion). They also replaced the splitter that was hooked up to my positive battery post with a better quality one. It seems to be running properly now for the most part: the radio's no longer cutting out, and it's no longer stalling or sputtering under load. I'm not sure how this relates to the battery incident (previously existing ground wires couldn't have simply disappeared), but as long as it's not cutting out or stalling, I'm not going to lose much sleep over that point in particular.

However, my 'check engine' light is still coming on intermittently. It only comes on while the truck is in motion, and it doesn't stay on for long periods at a time (ranging from brief flickers to staying on for 2-3 minutes or so). It also seems to loosely correlate with electrical load: it comes on more frequently with the radio / lights, etc on, and sometimes it goes off immediately corresponding with turning off the headlights. If I can get the CE light to come on while not in motion and for long enough to check the diagnostic codes, then I'll report back with those, but I don't think that I'll be able to do so.

Any thoughts / suggestions? Perhaps the ECU is still confused and needs to be replaced? Perhaps it's still not properly grounded and I need to install more ground wires? Perhaps it's something else entirely?

The 'check engine' light is now staying on more consistently, so I should be able to read the code once I get a working multimeter (I didn't realize that mine no longer works). Hopefully the problem should be more obvious once I get the code readout.

Luckily my headlights now stay on at the expected brightness without flickering.

The 'Check Engine' light is now staying on consistently, but at least I was able to pull the codes with an analog multimeter. It's throwing code 13 and 43, which is 'intake air temperature sensor' and 'EGR', respectively.

I've checked the resistance on the air temperature sensor (hair dryer and all), and it seems to be fine. Also, AFAIK, mine is not the California model, so I've no idea what the California-only 'code 43' would mean on a non-California truck. The only thing that makes sense is that the ECU might be confused from the short. Otherwise I'm stumped.

Regardless, I think that the check engine light headscratching is a different enough topic that it needs a separate thread.

Thanks all for your help up to this point, I appreciate it. I'm still learning, and this whole thing had me completely baffled.