computer problems

[flipster125]

Ok, I'm having problems with my 89 Blazer 4.3L TBI 4x4 Went to go one day and truck didn't start...

As far as I can tell, the computer is not pulsing the injectors, resulting in the no gas getting into the motor, which then of course doesn't run

This is a list of what I've tested...

-Constant 12V to the injector when key on is ok.
-Put 12v onto the injectors via jumper wires, they do infact open and squirt gas.
-Tested wires between injectors and computer for continuity, they're good.
-Tested the computers 3 ground wires, they all read as ground.
-Checked for stored engine trouble codes... there are none. The computer flashes 12 over and over ("Engine not running", supposed to indicate that the computer is working ok)
-TPS sensor is good, Voltage goes up and down with throttle opening
-didn't test the temp sensor, but my temp gauge works in my dash, so I would assume it works

After testing all these things (didn't actually "change" anything, though I had unplugged the computer for a bit) I decided what the hell I'll try starting it again, and it started :| However it was EXTREMELY rough, wouldn't hold idle, was missing left right and center, and died after about 40 seconds. (and incase someone thinks it, it wasn't running off the gas I squirted in when I was testing the injectors, I only squirted a teaspoon or so)

Since then I'm back to where I was, she just cranks and cranks and cranks and never squirts any gas into the motor (I can see it as it's TBI, and the injectors just sit there doing nothing)

Also, it did this a few months ago, and fixed itself after a day :| No luck this time, been 3 days

Anyone have any ideas? And if I need to replace the computer, do they make (cheap) aftermarket replacements? I wouldn't need some super performance chip, just a replacement...

Thanks

[MT-2500]

Originally Posted by flipster125

Ok, I'm having problems with my 89 Blazer 4.3L TBI 4x4 Went to go one day and truck didn't start...

As far as I can tell, the computer is not pulsing the injectors, resulting in the no gas getting into the motor, which then of course doesn't run

This is a list of what I've tested...

-Constant 12V to the injector when key on is ok.
-Put 12v onto the injectors via jumper wires, they do infact open and squirt gas.
-Tested wires between injectors and computer for continuity, they're good.
-Tested the computers 3 ground wires, they all read as ground.
-Checked for stored engine trouble codes... there are none. The computer flashes 12 over and over ("Engine not running", supposed to indicate that the computer is working ok)
-TPS sensor is good, Voltage goes up and down with throttle opening
-didn't test the temp sensor, but my temp gauge works in my dash, so I would assume it works

After testing all these things (didn't actually "change" anything, though I had unplugged the computer for a bit) I decided what the hell I'll try starting it again, and it started :| However it was EXTREMELY rough, wouldn't hold idle, was missing left right and center, and died after about 40 seconds. (and incase someone thinks it, it wasn't running off the gas I squirted in when I was testing the injectors, I only squirted a teaspoon or so)

Since then I'm back to where I was, she just cranks and cranks and cranks and never squirts any gas into the motor (I can see it as it's TBI, and the injectors just sit there doing nothing)

Also, it did this a few months ago, and fixed itself after a day :| No luck this time, been 3 days

Anyone have any ideas? And if I need to replace the computer, do they make (cheap) aftermarket replacements? I wouldn't need some super performance chip, just a replacement...

Thanks

Is it losing spark and injector pulse or just injector pulse.
If just injector pulse.
Give it the old tap or twist test. Pull the pcm down and tap and twist with both hands on the sides of it and see what it does.
If you need a pcm they aftermarket parts has them 79-100 $
Do not forget to save and change your old prom to new one>
MT