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Will not start! (SOLVED)


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87 Conquest. Over the past few weeks, ignition would intermittently cut out (for about half a second)- just like a little blip~ and then fine.

 

A couple days ago, it cut out again just as before, but this time, the it was as if the ignition shut off completely. Starter runs, no fire. Just stopped running in an instant.

 

Towed the car home, ran many checks with much help from the Virtual Mechanic.

 

I have spark- the tach does bounce while trying to start.

 

I have good fuel flow and consistent pressure, fuel relay operating as normal.

 

Injectors are spraying, removed the pipe over the valve cover and can see primary injector spray pattern is OK.

 

Ignition timing is dead on. Removed valve cover to verify timing chain. Perfect.

 

Self diagnosis indicates a code 1 and a code 5. (TPS error)

 

A check of the TPS indicates good sweep.

 

Found a high ground from the motor to body/battery ground in the area of 40 ohms. Corrected this with a new ground strap.

 

Compression check indicates between 130 and 140 on each cylinder.

 

So, what sort of electrical anomaly would cause the engine to simply 'cut off' (not bog down like it was running out of gas) it just 'turned off'- and while the laws of physics would dictate that I have everything necessary to fire a fuel charge, I get absolutely nothing. Suspected knock box, except for the fact that I have spark and tach action. Months ago I opened up the knock box and reheated several suspect solder joints. It's the stock '87 unit. Between this unit and an ECM, these components are FAR too expensive to try throwing parts at this car... but I'm running out of ideas.

Edited by Sharpshifter
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I read that this component might become a problem, so took time to dismantle and resolder the board when I bought the car.

 

Right now I am getting spark. Can the knock box fail in such a way where a spark is produced but will not allow the car to run?

Edited by Sharpshifter
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Very good point. Without checking that I have verified good fuel volume and pressure. Disconnecting the fuel return line I am able to about fill a mason jar with fuel in under 20 seconds.
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WEAK SPARK.

 

Throughout all of this, repeated checks with the timing light told me there was a regular spark. Pulling the primary wire and arcing to ground told another story.

 

A weak orange fizzle. Guess what else, printed boldly on the coil body was "REQUIRES EXTERNAL RESISTOR." :mellow: It's a points ignition system coil, probably well overheated and damaged by a steady 12v supply.

 

Replaced it with the proper coil "FOR ELECTRONIC IGNITION" and it runs fine.

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