Electrical Problems**UPDATE** TRUCK DIED!! need more help

[K10 KRAWLER]

This past weekend Was my first time bringing my truck out on the trail. It performed quite well, except for one fact. any time I put a major draw on my electrical system (Like My Winch or electrical fans) the truck sputters, backfires and Just wont run at all! I have 2 Batteries run in parallel (one is new the other about 2 years old).

to go deeper into it, I noticed that the truck only does this under 12-13 volts. For example, i would drive at full throttle and switch on my fans, and the truck sputters and backfires. If i drive it with hardly any throttle at all, turn on the fans and wait for the volts to reach 14 again the truck will drive fine. As for using my winch, my truck wont run at all while winching, it just backfires and dies.

I have a fuel injected 350 from a 93 in my truck, I tried changing coils and that did nothing, so anyone have any ideas?

 

[apache]

One thing that comes to mind is when running dual batteries that are not isolated replace both at the same time or the weaker/older battery will take out the other.

 

[Fordum]

OK, basically what it happening is, your computer is getting starved for volts<G>.
Assuming that your batteries are charged, there should be no way for you to draw the voltage down that low under normal loads. Without smoking something. You either have a bad battery or a bad connection somewhere.
Turn the truck off, being sure you are somewhere you can get jumped off just in case. Put a voltmeter across the battery terminals. Should have 12 volts or better. Turn on some loads. Headlights, Air con fan, etc. Battery should stay around 11.5 to 12. If not, your battery is either not being charged by the alternator or is shot. If you have good voltage there, look at your dash gauge. If it shows less than the other voltmeter, you have a bad connection between the batteries and the rest of the truck. I would suspect a bad ground close to the batteries or where the engine gets its ground. If the ground cable for the batteries is hooked to the frame or the body, try running a heavy ground to the engine.
The computers have to have a certain voltage to work.

 

[K10 KRAWLER]

Ok so my truck left me dead last night, I took it for a little spin, (with a new battery) and the truck still did the same thing... but as I drove the backfires got worse and worse and then suddenly the truck died with no spark, So any ideas what I should start replacing?

 

[chevyuser74]

if your charging system is ok, and batteries as well, my guess would be ignition control module, but a little testing wouldnt hurt before u start throwing money at it. are the injectors spraying?

 

[katugly]

Yup im with Chevy User on this ICM. My 92 silverado did the same thing on the way home sputtered like it was missing or running out of gas or something limped it most of the way home but then it just died. It would start and run but when you started going it would run rough then die.

 

[K10 KRAWLER]

Yes I am getting fuel, just no spark.... I went to the pick n pull today and grabbed a computer and coil from another truck. still nothing, which part is the ICM? is it the computer that I swapped?

 

[chevyuser74]

it would be under the dizzy cap, has two weatherpack connectors going into it. its got two bolts holding it to the dizzy and i believe there is some prongs going to wires in the dizzy.

 

[K10 KRAWLER]

WHOOT!! thanks, I just happened to have a spare dist assy in my basement, i switched them over and its running again!! i just need to check my timing and then im good to go

 

[chevyguy82]

i had the same problem 2 weeks ago when on a wheeling trip. truck just died on me. tracked it down and found no power going to coil on distributor. took wire from distributor and ran it directly to a toggle switch that went to my electric fan mounted on dash. flipped the switch and she ran great. i must have melted the wire supplying 12 volts to coil. i haven't had a chance to track it down but i kinda like having the switch to coil. hope this helps.