WTH? Intermittent start problem

[mikkelstuff]

A few weeks back I was working on my 2002 Ranger 3.0L installing a flush out tee in the heater hose. Strangely enough the truck would not start when I finished. Hunting around I pulled on the connector to the coil pack and the connector pulled loose. Pushing the coil pack connector back in place, the truck started with no issue.

I really did not think the coil pack connector was loose but I did notice that the lock tab was broken out of the coil pack connector. After some fiddling around, I found a way to secure the connector with a wire tie.

A few weeks later I drove the truck to a store, came back out, and the truck would not attempt to start. The wife came to rescue me when I remembered the coil pack connector. So I cut the wire tie, reseated the connector, and the engine started with no issue. Now thinking the wire tie was inadequate, I devised a way to secure the connector with a long #6 machine screw and two washers.

So today the same problem but more so. I made stops at four stores and each time I returned to the truck it would not start without me pulling and reseating the coil pack connector. Luckily I carried a nut driver with me just in case I had to remove the #6 machine screw nut.

At my last store stop, I drove into the parking lot, shut off the engine, and found that it would immediately restart. Then more of the same - into the store, back out to the truck, and no start without pulling and reseating the coil pack connector. Clearly the connector had not worked loose with my driving. Furthermore, the engine has never quit while driving.

Note also that the truck always starts immediately after setting all night in the garage.

So what is the problem? I not longer believe this is a loose connector problem. Can a bad coil pack be doing this? I am stumped - not to mention exasperated!

 

[Davejb]

Possibly a bad wire going to the connector or issue in the connector itself? When you unplug it the wires get jostled & connection is restored. I'd probably get a new connector. Rock Auto has the Motorcraft part for $25.

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[Uncle Gump]

It could be a loose terminal on the coil itself.

 

[mikkelstuff]

I just do not understand with a loose wire in the connector how it can restart immediately but fail after a 10 to 20 minute wait. Nonetheless I did order a replacement Motorcraft connector. It could use that anyway.

 

[Davejb]

I just do not understand with a loose wire in the connector how it can restart immediately but fail after a 10 to 20 minute wait. Nonetheless I did order a replacement Motorcraft connector. It could use that anyway.

Welcome to electrical gremlins, maybe heat/cooling expansion/contraction related? Good bet it's the connector or the coil as Gump suggested.

 

[lil_Blue_Ford]

Definitely sounds like electrical gremlins. They can be a nightmare or an annoyance. Good chance it’s a bad connection, and the plug having a broken lock tab is certainly suspect. It may be possible that there’s a bad connection inside the plug.

But, it could be just about anything else, including bad/corroded ground wires. I had a bunch of weird electrical issues with my one truck, chased the problems with no real answer for quite some time. I was certain it didn’t have a problem with the battery and frame ends of the ground, that was an easy enough thing to pull the ends, sandpaper things off and put a dab of dielectric grease on. Then as I pulled the battery terminals because the battery was dead, again, I realized the cable was crunchy. Skinned off some insulation and the dumb thing was corroded end to end in the insulation. Replaced it and that was the end of those problems.

 

[RonD]

Its for sure the 12volt connection(red wire) that's the issue because engine would still start if 1, or even 2, of the 3 ground wires were losing contact, it would run rough but would start/run
The loss of 12volt wire is the only connection that would cause no spark
And it could be the pin IN the coil pack, these run VERY hot, so loose connector doesn't help but re-seating it may restore the 12volts needed by coil pack

In 2002 3.0l Ranger the 12v at coil pack comes from PCM relay in engine fuse box


And it might be the Crank sensor or Cam Sensor
Watch the CEL(check engine light)
It will come on with key on, means PCM has booted up
And it will GO OFF as soon as PCM(computer) gets a timing pulse from crank sensor and cam sensor, so when starter motor starts to turn the engine, CEL should go OFF instantly, if not then no spark, or fuel injectors

 

[Davejb]

Is the actual connector the same? (I don't see how with 7 vs 4 conductors), does the part number on the bag match?

 

[mikkelstuff]

Still more gremlins:

Replaced the coil pack connector AND the coil pack since I did not trust it. This made no difference at all. Same no start sequence.

Disassembled and cleaned the main ground wire cables where they are mounted on a green coated stud just forward of the battery on the stamped metal cross member. I made two trips and the truck started each time! Hurrah!

Drove the truck to the library today and the same old no start problem. Pulled the new ignition coil pack connector, reseated, and immediately started. Sheeeezery!

Watching the dash instruments while spinning the starter under the no start condition I see that the CEL light has gone out. I also note that the oil pressure gauge needle jumps wildly from peg to peg. I would think this to be a bad ground issue but where?

Any chance this is the PCM relay in the engine fuse box?

 

[mikkelstuff]

With great help from RonD I believe I have isolated the problem to the PCM. Pulling and reinserting fuse F1.21 (power to the PCM) will always restart the engine.

Strangely enough though I've had no more starting issues since the Colorado weather has turned off cooler. There are time though when I think the no start gremlin has hit again but the truck starts on a second try with the ignition key switch.

Still I do not trust this PCM so have sent it in for testing and repair. My guess is a loose internal connection. I will post the result in case someone else is hit with this gremlin.