Hi folks. I have a 1999 Navigator that keeps blowing #8 coil and #30 fuse inside fuse panel. The coil will blow within 3 to 20 minutes. The fuse will blow soon after. If I keep changing the fuse I can get home when this happens. I was told it was the remote starter so I disconnected it and all went well for five days. Then it started again today 7/16/11. As soon as I put the fuse in and turned the ignition switch on (without starting) it would blow the fuse instantly again. When the engine cools down it will not blow the fuse until it warms up. I have gone through 6 coils (used ones). Do I have the trace all the wires that I disconnected from the remote starter. I will have to disconnect the injector from this cylinder so fuel will not enter this cylinder. Please help Thank you
I have read about spark plug problems with the Ford and Lincoln engines. The spark plugs may at times get corroded at the plug threads and may possibly blow out of the head. This could cause the high resistance to the coil. Removing the plug and cleaning the threads with a thread chaser and installing a new plug may help.
The electrical schematics show that all of the ignition coils get their voltage from the same circuit. I would think if one coil had problems they all would have problems. A coil can burn out from high resistance. If the spark plug is faulty (high resistance) or is poorly grounded in the head then the resistance could be high enough to burn out the coil. A mechanic with a scope would be able to see the problem by looking at the scope pattern and comparing it to all the other coils patterns. As of blowing out the number 30 fuse, it sounds like two different problems.
The #30 fuse includes the theft deterrent, instrument cluster, PCM power relay and PCM power diode, radio noise capacitors #1 and #2. Eliminating these from the circuit one at a time will help find the faulty part. Some of these parts like the radio noise capacitors are in the coil circuit but not pin pointing the #8 coil.
Check out some of these suggestions and let us know about your progress.
Thank you for your answer. The only time the #30 fuse blows is when the #8 coil goes bad.Today I disconnected the #8 fuel injector wire so fuel would not enter the cylinder. I let the engine run until warm and wiggled the coil harness and the fuse went out. I did this 3 times. There were times today I would wiggle the coil harness and it would not blow. (this could be a coincidence). Where is the PCM power diode? I have a 2001 Navigator with a bad engine. Do you think it would work in my 99 Navigator? I changed the plugs and the #8 coil about 5 months ago and worked fine until 2 weeks ago. Thank you so much for the help. I did auto repairs from the late 60's to early 80's. Now I am 60 years old and do not have the patients that I had when I was younger (or the knowledge) It was so much easier then it is now. I did go back and removed all the wiring from the remote start and re-taped all the wires. (found no issues).
I would keep looking at the coil harness. If you wiggle it and it blows the fuse you most likely have a wire inside the harness touching ground. Work your way back from the coil and pay attention to the harness going around screws, sharp body parts, brackets and so on.
The battery junction box is next to the master cylinder.