ECM B fuse

[1993blazerlt]

I am trying to figure out what is caused my ECM B fuse to blow. In the few weeks before the fuse went out the battery was draining very quick so i did a load test and a alenator output test both passed fine. But the battery still drained its self. So after i drove it 300 miles home i had to jump it the next morning to get it to crank. I then drove it to the store and tryed to start it and all it would do is crank and crank. So i checked for fuel pump and spark and got neither. I looked at my fuses and found the ECM B melted. I replaced it and got fuel but still no spark. I am thiniking that my computer took a voltage spike and is toast but i am trying to figure out what caused it so i do not fry another computer when i put one in. This is on a 93 blazer with CPI

[mrmidnight]

blazere have you tried just replacing the said fuse? It could have been the stock fuse and it just lasted too long and eventially the fuse got a case of high resistance (which if anyone wants an explanation, ask me, I know fuses don't have resistance) got too hot and melted the sucker, try just replacing the ECM B fuse and see what happens.

[1993blazerlt]

I did and the fuel pump worked but i still had no spark

[Sparky2263]

I'll get you some diagrams if you can wait 'til this evening.

[Sparky2263]

Day late, dollar short....................

Here ya' go.

http://www.sicgmtrucks.com/forum/attachment.php?attachmentid=1659&stc=1

[1993blazerlt]

well i am very confused now I took my computer out and put it in my friends CPI blazer and with my computer his blazer got spark and would run. So i am guessing that my computer is good. I took the ignition modaul out and had it tested at a autoparts store and it was fine. I hooked up my friends brand new coil and i would still not get spark in my truck. I am thinking maby pickup coil? but i don't think the pickup coil has any thing to do with ECM B fuse

[1993blazerlt]

OK i got a chance to check a few more things. I checked power going to the coil. Out of the three wires that should get power when ignition is on i am only getting power from the big fat pink wire which is ignition power. I then checked the voltage on the large connector going to the ignition modual and i had nothing at any of them. I know the computer is good because it ran my friends s-10. I have checked all my fuses what could i be missing. Has any body run into this same problem?

[Sparky2263]

Disconnect the ECM. If you still have no spark, it ain't the computer.

You should have 12V going into the coil on the big pink wire and 12V leaving the coil on the small pink wire going to the ignition module. Here's another diagram.

http://www.sicgmtrucks.com/forum/attachment.php?attachmentid=1665&stc=1

[1993blazerlt]

well i finnaly figured it out it was the ignition modual which autozone had said was good thoes idiots

[Sparky2263]

It's not them, it's the tester itself. The parts store testers test for the switching ability of the module with no load. Problem is, the module carries a helluva load under normal conditions.

The best (and only for me) test is on car.

[9BALL]

I Had A Very Similar Problem A Few Days Ago On A 93 Vortec 4.3 Cfi Blazer . Intermttent Operation And Finally No Spark Ever. I Replaced The Entire Ignition System ( Distributor, Pick Up Coil, Ignition Module, Ignition Coil , Switched To Bosch Platinum +4 Plugs, Plug Wires Were Ok ) As Well As Replacing The Alternator. 12vdc Existed At Pnk Wire To Coil With Ign On And 12vdc At Ignition Module. Engine Ran But Stalled Immediately. A Timing Check Revealed Random Advance And Retard. I Disconnected The Tan/blk Stripe Ignition Control Wire Under The Air Ducts On The Passenger Side And The Engine Ran And The Timing Stayed Where I Set It On Cyl #1. ( Good To Know If U Are In Bfe) Unfortunately There Was No Advance Of Course But The Engine Ran And The Blazer Was Drivable. I Took It To A Shop And They Fixed It But The Are Very Reluctant To Tell Me What They Did. I Checked The Timing When I Got Home And It Appears To Be 38 Degrees Btc At 2000 Rpms /engine Hot With Tan/blk Stripe Ign Control Wire Connected. Now Im Spooked. Vaccuum Centrifugal Advance Ignition Anyone?.
Maybe Some Of This Info Will Help.
Ttyl.

[Maximus]

Sorry I didn't see this thread before because I could have told you don't go by what the idiots at Autozone say.To prove a point to a friend about them I took one bad module to them and they said that it tested good.I then took one good module to them and they said it tested bad.I swear they couldn't stick their thumbs up their ass right if they tried.Autozone got in some big trouble here while back for pulling codes for customers then selling them a part saying that it would fix it the problem.Needless to say that 9 out of 10 times they were wrong and the people had to get a real tech to diagnose and fix the real problem.They had people believing that if the scanner said a certain sensor was reading a problem that they needed to replace that sensor.It didn't take very long with that stupid analogy for them to get sued.These discount parts stores really need to start hiring some qualified employees instead of the average Joe off the street who can barely change his own oil.If they can't pass the ASE parts specialist test then they shouldn't do any thing more than work a cash register in my opinion.I worked at both Autozone and Advanced.At Advanced I was one out of three that was ASE certified.And at Autozone it was only me and a older fella who had been in the business for 30 years that were ASE certified.Hell the store managers last job was at managing a Office Depot for crying out loud.He was always asking me to come help a customer who had a question because he didn't know what they were talking about.Man would it piss me off he was running the place.Anyway end of my rant on that lol but you get the idea.

[9BALL]

I Always Karry A Spare Ignition Module Wherever I Go. Better To Have It And Not Need It Than Need It And Not Have It.

[1993blazerlt]

yea i know the people at autozone are complete idiots but i watched them do the test on the modaul. Autoaone is good for somethings i have used them to pull codes for me before and then they try and sell me the parts i never by them because most of the time it is not the sensor like the time i had a stuck EGR they tryed to tell me i needed a $330 EGR valve and all i did was run a little seafoam and it was fine. I do like the warentys they offer though. I have plenty of things from them with a lift time warrenty including brake pads i mean that is great they give you new pads and all you do is bring in the old ones