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Tech501
Tech501, Auto Service Technician
Category: Car
Satisfied Customers: 747
Experience:  38 years exp, ASE Mastertech with L1 Advanced Engine performance
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10 Blazer: I have an 85 chevy S..wheel drive..liter..restart

Customer Question

I have an '85 chevy S-10 BlazerXXXXXwith a 2.8 liter 6 cylinder engine. A week ago I was driving and the engine backfired and died. It doesn't restart and doesn't even begin to catch. I checked to see if there was spark to one of the plugs by holding it and grounding the threaaded part of the plug to the engine block and having someone crank the engine. I then checked to see if there was electricity coming from the coil to the center tower of the distributor by connecting a wire to the terminal at the top of the coil and cranking the engine and holding the wire close to a bare spot on the cars frame. When that produced nothing I grabbed the terminal itself and had an assistant crank the engine. I felt nothing so I assume that means there is no electricity coming from the coil to the distributor. I had the alternator tested and it was only putting out 11 amps so I replaced it (alternator), I replaced the coil and for good measure I replaced the spark plugs. I still have no juice to the coil. To formulate the question precisely what sends electricity to the coil? What should be tested or replaced next? And where is it located?
Submitted: 11 years ago.
Category: Car
Expert:  Tech501 replied 11 years ago.

Is this fuel injected or carb?


Check to see if you have 12v at the +side of the coil with the key on.

Customer: replied 11 years ago.
Reply to Tech501's Post: It's carbeurated. I have two seperate two-tanged plug-ins that enter the coil. Is there a way to determine which is the + side? Thank you for the follow up 501.
Expert:  Tech501 replied 11 years ago.
Just see if either side has 12v with the key on.
Customer: replied 11 years ago.
Reply to Tech501's Post: New to voltage testing. But I bought a Sperry digital multitester 350a and tested the multitester across the battery terminals and got a reading of 12.47 when it was set at 20, so I know it's testing accurately. I got all zeros when testing all of the incoming terminal tangs at the coil. With the key on. No juice to the coil.
Expert:  Tech501 replied 11 years ago.
You need to put the black probe (if colored) on the negative battery terminal and probe the coil terminals with the other while the key is on. If your not familiar with testing electronic circuits, this is going to be very difficult for you to understand if we get into troubleshooting..
Tech501, Auto Service Technician
Category: Car
Satisfied Customers: 747
Experience: 38 years exp, ASE Mastertech with L1 Advanced Engine performance
Tech501 and other Car Specialists are ready to help you
Customer: replied 11 years ago.
Reply to Tech501's Post: I'm at work until 6:00 p.m., but will do the testing you described tonight. Am I still looking for voltage or am I now testing for an open circuit? Are there any components other than wiring that could have failed between the battery and the coil? My memory is not always entirely reliable but I seem to recall that we had a very similar problem with this same vehicle eight years ago. My wife was driving the car then, she called me from a parking lot that was right next to the GM dealership, and if I recall correctly we eventually replaced something on or near the firewall that corrected the problem then. Unfortunately, nothing looked familiar to me as I started disassembling the car 5 days ago.
Expert:  Tech501 replied 11 years ago.
We're just trying to find out what is working correctly and what isn't. If you not getting any spark then we need to know if the coil is getting power first. If it is then we will need to know if it is getting pulse. If it isn't getting power, then we will proceed in a different direction.
Customer: replied 11 years ago.
Reply to Tech501's Post: Pulse?
Customer: replied 11 years ago.
Okay Tech501, with the voltage tester's black lead plugged into the "com" and the red lead plugged into the "V", and the tester turned on and set to the 20 volt position, and the Blazer's key turned to the on position, I put the black probe on the negative battery terminal and tested each of the 2 prongs on both plug-ins that push into the top of the new coil. and didn't get any reading. So, if the testing as I described it was performed correctly, there doesn't seem to be any current getting to the coil from the battery. What's next?
Expert:  Tech501 replied 11 years ago.

That power comes directly from the ignition switch so you'll have to trace it back and find out why it isn't gertting to the coil. Here's the schematic.












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