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Mercury Mountaineer 5.0 Has No Spark Every Morning

I have a 1997 Mercurey Mountaineer 5.0. In the morning it has no spark. If I disconnect the negative battery cable for 45 minutes or so and reconnect it, then it has spark and starts and will start and run perfectly every time all day. When it sits overhight, no spark. Same story every day.

Sounds like the PCM, the engine control computer…I can’t think of any other parts that would respond to disconnecting the battery like that…Has the check engine light ever come on?

Never.

Go and get your engine codes read any way at a parts store. since you disconnect the battery it may be a pending code not yet ready to set the engine light.

Check the ignition system and make sure power is getting to it while the trouble is happening. If that is ok then see the ignition pulses are there.

When you disconnect the battery, you are also resetting the PCM to its default values, and that restores spark…Does it have a factory anti-theft system?

Yes, it has the PATS system. It has no codes.

Yesterday it started in the morning without disconnecting the battery cable. This morning it will not start. I have to hood open and it is getting direct sunlight. I am guessing that it will start once it gets some sun. Bizzare.

1997 ? Yep, she’s a teen-ager.
Gets up & going when she dang well feels like it.

The trouble most likely really isn’t so bizarre. The trouble is most likely due to a bad connection somewhere with the ignition system. By performing logical testing procedures they should lead you to the source of the problem.

That is so true, but are there any parental tricks I can try? Does the key on this year have a microchip?

Yes the key has a microchip which would not be an occasional malfunction.
Along cougar’s line of thinking…time of non-operation being a factor…I’d look at the ingnition switch as a possible culprit. ( not the key and cylinder, the SWITCH further down in the column. )

I’ve even had HUMIDITY play a factor in temporary elctrical outages. Then in the dry eveything functions par-normal.

My daughter on the other hand, is another story.

Yeah it could be a flaky ignition switch. When it wont start turn the key to run & check for 12 volts at interior fuse 19 (25 amp mini). The fuse is between the ignition switch & the ignition coils.

FWIW if the “remote anti-theft personality module” thinks the truck is being stolen it opens a relay between the ignition switch & the starter so that it wont crank.

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Thats an interesting thought from Caddyman, maybe the PCM needs a good dope slap every morning.

Another mechanic suggests ;
when moving the negative cable you’re moving other wires as well. Try leaving the cable on but wiggle, touch, and move wires nearby. particularly focus on the crank position sensor plug. ( wires running to the engine front cover, right side just above the crank pulley. )

Sounds like a problem with the car’s anti-car-theft security system. These kind of problems usually require dealer assistance.

I really have to say replace the spark plug wires, I MEAN MAJOR CLUE, big rain will not start, see previous post.

I am leaning towards the PATS. Started Monday and Tuesday morning when unlocked manually with key. Today no start on same routine. Currently hood up taking in some sun.

12.2 volts at fuse 19, no spark.

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Disconnect battery wait 1 1/2 hours. Reconnect, no start. Lock driver’s door. One hour later - open driver’s door with key. Turn to run. press gas pedal once. Starts. Now it will start all day and run perfectly. It would start 100 times today if I had that many stops. Tomorrow morning I bet will not start. Will try same procedure in the AM. Only difference here is pressing the gas. If it starts on this procedure tomorrow, maybe I got somewhere. I doubt it.

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