Pulling my hair out

[rogerd27]

90 Jeep Cherokee 4.0 AT pain in my......... I have replaced the CPS, ignition coil and module, chased down every wire related to the ignition back to the ECM checking for continuity. My problem is I have no fire at the plugs. I have fire to the coil but no spark. Is my ECM fried ? This is a recent project I acquired cheaply and dropped in a used motor becaused of water in the oil, my problem is I dont know what things were wrong prior to the headgasket. I'm a newbie to here and any response is appreciated

[Jay83LeSabre]

Well since you have power into the coil and no power out of the coil. I'd change the coil.

[Dale Aeppli]

Originally Posted by rogerd27

90 Jeep Cherokee 4.0 AT pain in my......... I have replaced the CPS, ignition coil and module, chased down every wire related to the ignition back to the ECM checking for continuity. My problem is I have no fire at the plugs. I have fire to the coil but no spark. Is my ECM fried ? This is a recent project I acquired cheaply and dropped in a used motor becaused of water in the oil, my problem is I dont know what things were wrong prior to the headgasket. I'm a newbie to here and any response is appreciated

HI, DO YOU MEAN YOU HAVE SPARK COMMING FROM END OF COIL WIRE TO A GROUND, OR DO YOU MEAN YOU HAVE VOLTAGE AT THE POSITIVE POST AND NEGATIVE POSTS AT COIL . IF YOU HAVE SPARK COMMING OUT OF COIL WIRE TO GROUND, CHECK THE CAMSHAFT POSITION SENSOR INSIDE DISTRIBUTOR. DALE
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[Stick89]

Read a post similar to this Saturday,not sure if this will be any help but the Dude had an old alarm(he didn't even know it was there)anywho there was a relay in the alarm system.The relay had "gone south"which evedently shut down the system preventing the engine from firing.
Said he pulled the relay and bingo it fired right up.I'll try to find the site and post it back here............

[rogerd27]

I should have been more precise, I have 12.7 volts at the coil but no high voltage output. I've replaced all the ignition components with new and still get no results. I'm sure I have fuel pressure and I haven't checked but the injectors sound like they are clicking. I'm a novice to Jeeps but I bought a Chilton manual and have checked everything wiring related the only thing I havent replaced is the cam sensor in the distributor, a friend of mine said it only told the computer the valve timing to spray the injectors is this correct or could it cause my problem? Another post I read had to do with the MAP does it regulate ignition dwell or fuel ratio

[ponchonutty]

Had one in the shop doing about the same thing. Noticed that like half the dash idiot lights weren't comming on either. Ended up being a faulty crank position sensor.

[Dale Aeppli]

Originally Posted by rogerd27

I should have been more precise, I have 12.7 volts at the coil but no high voltage output. I've replaced all the ignition components with new and still get no results. I'm sure I have fuel pressure and I haven't checked but the injectors sound like they are clicking. I'm a novice to Jeeps but I bought a Chilton manual and have checked everything wiring related the only thing I havent replaced is the cam sensor in the distributor, a friend of mine said it only told the computer the valve timing to spray the injectors is this correct or could it cause my problem? Another post I read had to do with the MAP does it regulate ignition dwell or fuel ratio

Usually when the crankshaft sensor is bad or going bad the engine will start. When the camshaft sensor the engine will not start till the sensor is changed dale [email protected]

[altenburgpj]

Originally Posted by rogerd27

I should have been more precise, I have 12.7 volts at the coil but no high voltage output. I've replaced all the ignition components with new and still get no results. I'm sure I have fuel pressure and I haven't checked but the injectors sound like they are clicking. I'm a novice to Jeeps but I bought a Chilton manual and have checked everything wiring related the only thing I havent replaced is the cam sensor in the distributor, a friend of mine said it only told the computer the valve timing to spray the injectors is this correct or could it cause my problem? Another post I read had to do with the MAP does it regulate ignition dwell or fuel ratio

The other side of the coil is the side controlled by the ignition system, and should be switching from 12.7 to zero with every spark. If this is not happening then you might just need to replace the coil.

Did you check the large ceramic resistor mounted to the firewall. It should be in the coil circuit during run, and bypassed during cranking. The resistor limits the coil power during normal running, and is bypassed during cranking so that the coil can make a strong spark even if your battery is weak.

What the computer does to dwell fuel ratio and so on is based on many things including the MAP.