Engine Cutting out and Lighting Flicker

[Keymo]

1993 Chevy K1500 Cheyene - 5.7l/350 TBI - 5spd manual - 4wd

Yesterday morning about a couple blocks from work, when taking off from a stop my truck suddenly started bucking. Let off the throttle and started running normally again. Gave the slightest amount of throttle and it would get going but any more than a hair of input from the accelerator pedal resulted in the bucking coming back.

This was at 4AM - noticed when the engine would cut out that all the lights on the truck would go out at the same time. Also noticed that as I was accelerating - without bucking - that the gauge cluster and stereo lighting would flicker and my gauges would randomly die/fluctuate.

I was able to get it the 20 miles home going down backroads. I found a good pedal position to keep the truck from bucking and still accelerate - painfully slow, but could get through the gears. Only took it up to about 40-45MPH though.
Being daytime I didn't have my lights on and I noticed that when accelerating the lights would now flicker slightly ON and when the truck would buck They would strobe on/off. Also the gauges would dance all over the place almost the whole time I was driving - settling down and going to the "correct" position a few seconds at a time before going back to dancing around again.

As I mentioned earlier - I could slowly get the truck up to 40-45MPH (didn't try any faster) and cruise just fine. If I was going a steady pace down the road - no matter what speed the truck ran great as long as I didn't need to accelerate. At idle - the truck would idle fine - never miss - things would start flickering if I stepped on the brake pedal or put it in reverse.

Thought it seemed like a grounding issue... Looked up ground locations and checked - they were all there outside of one strap that runs from the back of the head to the firewall. It had rubbed through/broken from getting caught between the firewall and headers the PO had put on. I got that one fixed - soldered a connector and a wire going straight to the battery. I also detached and brushed the connectors and grounding points for all the grounds.

Took the truck out again and still did the same things...
I should also mention that Since I got the truck (about a month ago) when I turn on the headlights the blinkers come on and stay lit and do not work. When the headlights are off the blinkers "work" but both always flash when I use the indicator. Not sure if it's related at all but thought it was worth a mention. I was planning to go through the headlight switch/wiring soon - ordered a new switch a week ago and should be here any day now.

 

[GoToGuy]

Are your battery connections clean and tight?
Do you've got a random loss of electrical power. Fluctuating gauges, with ignition and or fuel cutoff. The headlight / turn signal problem. Try to duplicate, and then pull turn signal fuse. Does that problem go away?

 

[thinger2]

Bad battery cable. The plastic coated battery ends on a side post rot inside of those ends.
They always look like brand new because the plastic doesnt rot.
The ring terminal inside of it rots.
That factory ring terminal has 4 punched lugs that dig into the lead.
The problem is that the battery cables are so heavy and so unrestrained that the entire system depends on those four lugs.
I could go on all night but it is a bad battery cable.
Loosing power intermitantly and throughout the entire system is a power problem.
Or an entire intermittant loss of ground.

Ypu have bad battery cables.

 

[Keymo]

Are your battery connections clean and tight?
Do you've got a random loss of electrical power. Fluctuating gauges, with ignition and or fuel cutoff. The headlight / turn signal problem. Try to duplicate, and then pull turn signal fuse. Does that problem go away?

They are clean and tight.
I'll definitely give that a try with the fuse and the headlight/signal issue though!

Bad battery cable. The plastic coated battery ends on a side post rot inside of those ends.
They always look like brand new because the plastic doesnt rot.
The ring terminal inside of it rots.
That factory ring terminal has 4 punched lugs that dig into the lead.
The problem is that the battery cables are so heavy and so unrestrained that the entire system depends on those four lugs.
I could go on all night but it is a bad battery cable.
Loosing power intermitantly and throughout the entire system is a power problem.
Or an entire intermittant loss of ground.

Ypu have bad battery cables.

Interesting! Never really thought about that... But it makes sense. They're definitely the OEM lead-molded cable ends on there... Looks like I'll have to go to the welding shop an get some decent cable... Might as well replace em all!

 

[Keymo]

Alright so finally got to spend some time in the K1500. Went and got 2/0 wire for the battery to starter, enough 4ga battery cabling to run a new battery to junction block on the firewall and all the ground straps I wanted to run and a couple of those battery terminals clamps with the ability to clamp and bolt to it.

Started by checking for continuity and resistances between as many points as I could. Wasn't really seeing anything concerning but decided I'd do some wiring updating anyway....

Completely rewired the headlights and replaced switch. Also replaced fan control - unrelated...
Had wondered if the headlight wiring or something was causing an issue because when you'd use the dimmer the gauges would do all sorts of wonky stuff depending where it was dimmed to. If I unplugged the dinner connector some gauges would drop and others would ster climbing... Very strange. But rewiring them did nothing.

Started by making cabling for replacing the starter cable (even though the starter always cranked fast - figured might as well!). Then made and ran a new battery to junction block. Went and turned the key to see if those solved it and still the same symptoms...

Since I'd already cleaned all the grounding points and connections I figured I'd just run brand new straps from battery to head, block and pulley bracket. Also ran ground wiring between grounding points - routed so I could wrap it in the factory loom ( some cases had to replace with my own larger loom). Some points had corrosion in the wiring so clipped all that back to clean copper and soldered new wiring in... Also added wiring between each of those points to battery. Figured why not go all out?

This time when I went to turn the key the gauges acted normal. Actually volt meter read higher than it'd ever had. Cranked her - starter strong and she fired up like normal. No issues with gauges or lighting....

Ran in to town to pick up some things and she ran strong and showed no symptoms as before.

Actually - turned the headlights on, fan at full speed and interior lights with the radio on as a load test and the gauge barely dropped below 14v. Since I've owned the truck with just the headlights on it'd be just below 14v and with the fan running at the same time it'd drop to just over 9v. Lights would dim significantly when the fan would be on low and even more on high. As far as I could tell at least the cluster lights were way stronger now than since I've owned it and they didn't change brightness at all with the fan.

Not sure what EXACTLY was the fix but definitely had to do with grounding... Goes to show you cleaning and checking ground might not always be enough....