Hey there CK5! This is my first post here...having some issues with my 89 K5 (TBI) that I just don't understand. I'll start it up and it just dies after a few seconds....reset the computer and it goes for longer (about 15 minutes). This happens going down the road or just sitting idling. It cuts out, and only starts if I turn the key back towards me, then start it again. If I react quick enough when it dies down the road, i can turn the key back to unlock then to run again and it refires without actually cranking it over....seems like my computer is fried but I'm uncertain. New dist. cap, rotor, module, magnetic pickup, and coil...as well as ignition switch. All grounds are good...connections, fusable links, etc....I'm stumped!!
CK5
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1989 K5 Blazer Randomly Dying
- Thread starter Jim M.
- Start date
When it dies idling, does it restart again immediately/easily? Any other symptoms? No power, idles rough, smells bad, etc.?
I thought about that. Gonna go to the junkyard today for a computer, I'll grab a relay too because why not.
I've seen more than a few in-tank electric fuel pump wiring issues,often the wire(s) from the fuse box back to the tank get all gangrene in one spot,or at the plug at the tank (most new pumps now come with a new plug)...the wire conducts enough amps to power the pump up briefly ,then heats up and the connection breaks and the pump quits--re-starting it sends enough of a voltage surge to run the pump again for a few seconds..
My friend had quite a few GM's in his shop for this issue and he used to just put a new fuel pump in assuming it was dying (they can create the same symptoms your having)--but after he was done installing them the vehicle would either have troubles again shortly after the customer got it back,or right away..
He learned using his digital volt meter to check for power at the pump wiring was not a good indicator of the condition of the wires--a wire with lots of corrosion or just a few strands still making contact can show a healthy 12+ volts on a meter,but fail to deliver enough amps to power the pump right..
He now uses a halogen sealed beam headlamp for a tester--if the wires can power the bulb for several minutes with no dimming or flickering ,then they are probably OK--I watched him test a Buick this way he had put a new pump AND the plug on the harness on,it stalled before he backed it out of the shop..
He asked me to get in the car,put it up on the lift,and had me turn the key on after he hooked the headlamp bulb up to the pump's hot wire and ground--it took about 2-3 minutes before it started dimming,then went out completely,and running his hand along the wire,he felt a spot that was hot and "mooshy",he cut it open and there was only a few strands left making contact,all green and powdered..
That car also had a bunch of ground wires for the ECM ,that was under the right side kick panel,all plugged onto a "bus bar" that was bolted to the sheet metal,that were all green and corroded--he cut them all back and stripped them bare and soldered a ring connector to all of them and put a new sheet metal screw to secure them to the body panel,after grinding the paint off to bare steel..that car had been in numerous other garages around town,and he was the only guy who "fixed" it for good!..
And he now tests the wires FIRST,before wasting a few hundred bucks on a new pump that may not be needed too!..(the pump he removed was in the car only a month or two and was fine,but the customer wanted another new one regardless while the tank was out--he also put in a new tank & sending unit as both were getting real crusty..)
My friend had quite a few GM's in his shop for this issue and he used to just put a new fuel pump in assuming it was dying (they can create the same symptoms your having)--but after he was done installing them the vehicle would either have troubles again shortly after the customer got it back,or right away..
He learned using his digital volt meter to check for power at the pump wiring was not a good indicator of the condition of the wires--a wire with lots of corrosion or just a few strands still making contact can show a healthy 12+ volts on a meter,but fail to deliver enough amps to power the pump right..
He now uses a halogen sealed beam headlamp for a tester--if the wires can power the bulb for several minutes with no dimming or flickering ,then they are probably OK--I watched him test a Buick this way he had put a new pump AND the plug on the harness on,it stalled before he backed it out of the shop..
He asked me to get in the car,put it up on the lift,and had me turn the key on after he hooked the headlamp bulb up to the pump's hot wire and ground--it took about 2-3 minutes before it started dimming,then went out completely,and running his hand along the wire,he felt a spot that was hot and "mooshy",he cut it open and there was only a few strands left making contact,all green and powdered..
That car also had a bunch of ground wires for the ECM ,that was under the right side kick panel,all plugged onto a "bus bar" that was bolted to the sheet metal,that were all green and corroded--he cut them all back and stripped them bare and soldered a ring connector to all of them and put a new sheet metal screw to secure them to the body panel,after grinding the paint off to bare steel..that car had been in numerous other garages around town,and he was the only guy who "fixed" it for good!..
And he now tests the wires FIRST,before wasting a few hundred bucks on a new pump that may not be needed too!..(the pump he removed was in the car only a month or two and was fine,but the customer wanted another new one regardless while the tank was out--he also put in a new tank & sending unit as both were getting real crusty..)
Probably waste of time and money, although spare ECM's aren't bad to have around. "New dist. cap, rotor, module, magnetic pickup, and coil...as well as ignition switch." didn't fix it, throwing more parts at it is going to get expensive. Especially if you grab wrecking yard parts and don't figure out if yours are bad first.
I'm ALL about spare parts, and swapping things out is sometimes easier than diagnosis, but you have to use known good parts. And even new off the shelf doesn't mean good.
Perhaps your ignition switch is out of adjustment?
No illusion that this will be easy to diagnose, but normally electrical stuff takes a bit of time to cool off before it starts to work again.
Ran longer with the new computer...but then went back to the same symptoms. I'm going to return my ignition system to stock by wiring out my MSD 6A box. It got soaked in coolant when my truck overheated and I didn't even think about it till now. I'm betting that's the problem.
Oh and just for the record I'm not the type of person to throw parts at something...the ignition switch, module, and distributor pickup were my only parts thrown...the rest of it failed within the past couple months. Coil tested good resistance wise, and the box tested good via a test made by MSD, but I'm still suspicious of the box.
That would suck. But from what I've seen on CK5 alone, not a fan of the MSD boxes on "stock" apps, they fail often enough that they are far more a hindrance than help. Usually easy enough to bypass.
Blackrhino2007
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First time post. I have a 1990 GMC Jimmy full size 4×4. I was having a driving issue for quite some time. It would randomly cut out on the highway when you hit a bump/pothole. I have been chasing this for a year with it getting worse. I thought I would start with a tune up, did not fix my problem. Fuel pump relay, ignition switch, no luck. Bought a Haynes gm book and chased all power...everything good. Finally I touched the power wire going from the Alternator to the ignition switch...it fell out of the connection! Finally...thank you Jesus!!
Blackrhino2007
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By the way, unhook the negative wire off the battery. I fixed the issue with the connection and was tighten things up and pop! I had grounded the power off the Alternator to the air cleaner. Now I have no power in the cab. Turned out to be a fusible link running between the alternator to the ignition switch. Fixed that and started the truck, it hasn't ever ran this good! BTW this is my wife's daily driver, she loves this thing. So while I was fixing/causing problems, I had her cleaning and sanding all grounds. Sorry for the novel and hope this helps someone. To that guy that has a Electrical issue, get a book on your truck.
