tom5170

98 k1500 z71, 5.7 liter with approx 294k on motor or at least on the body.

the alternator is brand new, brand new battery cables, New ignition switch, New fuel pump, New fuel filter, cleaned the fuel injectors, New spark plugs, New plus wires, etc. Also has brand new lifters. I went through the entire top of the motor and replaced everything that needs fixing, although I didn't replace the ignition coils.

here's the thing; it has a starting issue. sometimes it'll fire right up first time turning the key. other times it'll fire up, run 1 sec and die - and when it does this, I always turn the key to off and turn it back over and it'll usually fire right up. if the engine dies and I don't turn the key to off position, and I just turn it over, the engine will just keep turning over without starting.

And another thing; sometimes the truck will randomly not start no matter how much it turns over. when it does this, I always have to put the battery on the charger or jump it and it'll fire right up. but it's weird because the battery isn't dead, and the engine turns over fine.


what could be causing this?

89scottsdale

Almost sounds to me like a weak sauce battery. if the battery dips below 11 volts i have seen vehicles lose their marbles. (CEL Lights, rough idles, misfires, random electrical issues, and bunch of crazy stuff.) Have it checked or swap with a good battery. also, If you didnt unplug the battery while doing all this you could have tripped something in the ECM, or forgot to plug something in.

Start by unplugging the battery for 10 minutes, reconnecting it, and trying again

double check all your connectors. one time i forgot a ground when i did a top end rebuild on my previous truck and everything that could throw a CEL Threw one.

if that doesnt work maybe your VATS is acting up. i think the resistors in the keys can go bad and throw things off too.. but i say this from logic not experience.

tom5170

I don't have that chip on my key. and in fact the battery is brand new as well. I even tested a newer battery from another k1500 and still the same.

tom5170

it was doing this when I first bought the truck so I went ahead and replaced a lot of crap. the battery, alternator, and the cables along with the ignition switch were the first things I did.

I'm about to just yank the motor and find another 5.7 and throw in it. this motor is gonna need bearings and the front and rear main seal replaced in it soon.

89scottsdale

Try swapping out your computer see if that works