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Spark Plugs Not Firing

Postal_Dave

Active Member
Joined
July 14, 2021
Messages
93
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City, State
Greenville, SC
Year, Model & Trim Level
1996, Explorer, 4.0
Background:
I broke a the #2 spark plug while changing my plugs in my 1996 4.0 XLT Explorer. I had to take off the exhaust manifold, the air intake, and a lot of the radiator hoses to get to this thing and to clean out the cylinder after getting everything out. I also used an endoscope to make sure I got everything out of the cylinder.
BTW: A reducer on a shop vac and a small clear tube that fits inside a spark plug hole and is flexible to coil around inside the cylinder is great for cleaning out a cylinder.

Today:
I finished changing the plugs and the wires, put the radiator hoses back on, filled the radiator, put the exhaust back on, and then the air intake. I then turned the key and it started right up. It ran fine, no clunks, no hesitation, nothing. The best it sounded is ages. I let it run so that the new thermostat would open and get coolant running through the system. (BTW: There are only two gallons of coolant in it right now, I was going to top off the radiator after the thermostat did it's thing and moved more of the coolant around.)

After idling for 5 minutes, I watched the temp gauge go up, then I heard the thermostat open and the temp gauge started to drop. I then turned on the heat and 5 seconds later the engine stopped like it was turned off. I checked the oil and it was fine, I turned the ignition off then back on and I heard the fuel pump. I tried starting it but it just kept turning over without even a hint of firing.

I took an old plug put it in the new wire for cylinder 4 and put it against the engine block and tried to start it but there wasn't a single sign of a spark. The check engine light is on when I turn the key to "On" and while the engine is cranking. I don't have a way to read the codes at home.

Any ideas?
Thanks for reading this and for your help.
Dave
 



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fuses all good? i remembee on a 1st gen someone had an issue like that, turned out to be the 30A eec fuse, not too sure other than that if they are correlated. coil pack good?
 






Update: I checked all the fuses and they are all good.
Today: It fired up after sitting overnight with the battery unplugged. Unfortunately, it turned itself off after 5 minutes again. So something is overheating and once it does, it tells the engine not to start again by turning off the spark. What could that be?
 






Update: I checked all the fuses and they are all good.
Today: It fired up after sitting overnight with the battery unplugged. Unfortunately, it turned itself off after 5 minutes again. So something is overheating and once it does, it tells the engine not to start again by turning off the spark. What could that be?
coolant temp sensor? whats that read? if it reads too hot itll richen and could stall
 






Time to hook up a scan tool and look at realtime data, except i don't know how much you can get on a '96.
 






coolant temp sensor? whats that read? if it reads too hot itll richen and could stall
1) it will enrich if it reads too cold, not too hot, and 2) the coolant sensor reading won't turn the ignition off. Please don't speculate.
 






1) it will enrich if it reads too cold, not too hot, and 2) the coolant sensor reading won't turn the ignition off. Please don't speculate.
alright, my bad. forgot which it was. and i didnt mean it would cause no spark, thats unrelated, but it could cause a no start, right? or is there somehting im missing? guess my post wasnt exactly related to the issue, it would only explain half of it, thats on me. also if it reads far too cold, could it add more fuel than it can take to run?
 






What kind of events would cause the ECM to shut down that engine?

I'm wondering if it's not a sensed temperature fault but rather, the change in temperature is causing loss of signal like the crankshaft position sensor itself, or wiring or connector to it, possibly disturbed when doing the prior repair work? You could measure for a low voltage AC pulse from it while cranking.

I suspect your check engine light on while cranking is because either the crankshaft position sensor signal isn't making it to the ECM or the ECM itself is faulty. Of course there are those bulk connectors in the engine compartment, might want to unplug, inspect, and replug those. 2nd gen issues? Try this first!

 






What kind of events would cause the ECM to shut down that engine?
i'm not too sure. if it reads too cold, and dumps too much fuel but that wouldnt cause no spark, so i was wrong. or if it reads too hot it will lean out too much. sorry for misleading though:(
 






Code readers are very cheap, and a necessary tool with these old Explorers. A code will point in the right direction for a fix...
 






2 gallons of coolant, what is the total system capacity for a 96? is it 4 gallons?
 






Yesterday: After it ran for 5 minutes, I left the battery plugged up and I bought a $40 scan tool from Walmart. It said there were no codes to be found. It didn't show any real problems after I tried to start it and all it did was turn over.
I let the engine cool for 6 hours and tried to stat it again. It just turned over but once again it did not fire up. So I unplugged the battery and left it for the day.

Today: I topped off the radiator and filled the reservoir, then I plugged up the battery and the engine turned over just beautifully. I then turned on the heat and let that run. The engine ran for 11 minutes like that and it was doing fine. The temp gauge never got above the C mark though.
I then turned off the heat and the temp gauge slowly started to rise. At one point the engine revved up for half a second but that was it. Otherwise it ran smooth for the next 3 minutes. As soon as the temp gauge hit the first line of the operating temp zone it shut down.
 






I've been chasing codes on the vehicle for a while now. O2, then EGR, then cylinder 3 misfiring. I would not be surprised if the Camshaft or Crankshaft Position Sensor, or any other sensor is the problem.
 






Yeah that sounds like wiring of some kind, maybe disturbed from the work to get to the broken plug. Check all of the engine wiring as carefully as possible, look for any breaks of the insulation, or loose connections etc.
 






Does the scanner show live data?
 






CDW6212R: The only wiring, besides the spark plug wires, that I touched while getting that broken plug out were the wires and connections for the air intake. The wiring that goes into the air filter housing, then the sensor on the air intake funnel. I did double check those wires and they seem fine. I'll look around the compartment for any problems though.

Josh P: I'd like to do a live data scan on it but right now I have to wait for the computer's memory to reset so I can start the engine. I tried using the scan tool to reset the memory but that didn't help.

To summarize: If I leave it with the battery unplugged for several hours and the engine is completely cool, when I plug the battery up, the engine will start and run until it reaches operating temp. If I turn on the heat, and keep the temp down, it will continue to run a lot longer because it takes longer for the engine to get to operating temp.
If I leave the battery connected after it stalls, it will not restart even if the engine is completely cool and hasn't been touched for 4 - 5 hours.

BTW: How many hours does it take for the ECM to clear after you unplug the battery?
 






iirc its 15 mins? i may be wrong though
 






I'm wondering if there are a few unrelated problems that happened to occur while you were working on the engine
 









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it says video unavailable
 






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