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Another weird one


BigMeatyClaws

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1985
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Ford Ranger
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So, background: 1985 2.8 with duraspark/gm 4 pin conversion. The truck was running great but now...
It starts just fine, runs fine for about 15 seconds, and then dies. I hooked up the spark tester and watched it as it dies. Spark starts strong, then gets weaker, then is barely visible, then goes out and the engine dies.

New and tested coil and ignition module, new plugs with .045 gap, newish plug wires, new distributor and cap/rotor. Any ideas?
 


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dvdswan

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How are the grounds? Any corrosion on the battery?
 

BigMeatyClaws

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Grounds are good, battery is good. 12.7 with engine off, 14 running
 

RonD

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Try running a 12volt wire from battery positive to Coil +

1985 may still have a Ballast Resistor or Resistor wire to lower the Coil's Voltage once engine is started
If the "resistor" is bad it may be heating up too much and lowering voltage too far

When Key is in START position Coil gets 12volts(well 10volts because starter motor is active, lol)
When key is in RUN(ON) position Coil gets 8volts thru resistor

Test voltage at coil +, key on engine off
If you see Battery voltage, 12.7v, then there is no resistor inline

Coil could be failing, if possible test Coil + voltage engine running, if it stays at 14v and spark fades then Coil is most likely the culprit
Red/green wire is the 12v wire that supplies the Coil, and it may still have the Noise Suppressor Capacitor connected, disconnect it and see if things improve
 

kimcrwbr1

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Are you running. TFI coil the square one? Just use the stock TFI coil then watch the voltage going to the coil and module stays close to battery voltage when running. You can wire the coil and module together key on pos.
 

kimcrwbr1

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Low voltage will kill the ignition module they require battery voltage.
 


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