Ignition coil fuse problem

[Larry Rivelli]

Hi,

Have not been here for awhile but I have run across a perplexing problem with my 1994 SHO. It is a 3.2 auto with a/c, pw,power seats, sunroof, cruise, etc. In other words, it is pretty well equipped. It has approximately 156,000 miles and still runs great. Here is my current issue:
Every now and then (last time was about 4 months ago) it will refuse to start. Everything else seems to work. It took some time but it was discovered that the 10 amp ignition coil fuse was blown. Replace the fuse and it starts right up. It did it again this morning. It ran for about a second and then died and would not start. Replaced the fuse and it started right up and ran fine. So, what I am trying to determine is what is causing the fuse to blow? Any ideas would be greatly appreciated. Thanks for your help.

 

[luigisho]

Do you have the wiring schematic? Anything shorting on that circuit could trip the fuse. For example on some setups the radio noise capacitor, CCRM, ignition coil, etc are all on that path. So you could have a failing part or associated wiring in the circuit. Need the right schematic for the parts and the wiring for that year. Also there are ignitions grounds and such at the PCM.

 

[Off Road SHO]

IIRC the coolant level sensor gets gummed up with sludge that floats on top of the coolant overflow bottle. That sludge shorts out the sensor's contacts and blows the fuse.

Maybe.

Tom

 

[Larry Rivelli]

You may be on to something with the coolant sensor issue. Mine has been a problem for several years and stays on all the time. I cleaned it but it is shot. Light still stays on. I did notice the light went from dim to bright after I replaced the fuse this time so you may be on to something. I have been told the sensor is unavailable. I check my fluid levels on a regular basis and don't need the light. Do you know if it can be disconnected without causing any problems? Perhaps that would solve my fuse problem. Thanks. Larry

 

[Larry Rivelli]

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Any ideas where I can get a wiring diagram for my car? Thanks. Larry

 

[luigisho]

There are factory EVTM manuals (electrical vacuum training manuals) floating around in paperback and electronic formats. I usually find ones for my older cars on ebay or from owners on this forum. You could ask on the facebook group for assist or scan/email of the pages needed. They are faster to respond these days. I don't know the differences between model years and wiring diagrams. The parts are all about the same across all the GENI&II platforms but something could have changed during some model year or the 3.2 automatic cars could vary slightly from the 3.0 manuals. I just don't know with enough confidence to say they are exactly the same and you have to make sure if you have the 3.0 it's the SHO dohc motor diagram vs the 3.0 Vulcan motor that were offered in other Taurus models.

You could always try Tom's (offroadsho above) idea first. It's easy and free to check the overflow coolant bottle top and pull the cap off with the sensor hanging at the bottom, and clean it up and flush the overflow some and see if that helps.

 

[Off Road SHO]

Just unplug the sensor. Electrical Vacuum Troubleshooting Manuals are all over EBAY and Amazon.

Tom

 

[Larry Rivelli]

Hello again,

I have ordered a wiring schematic which is on the way. In the meantime, I pulled the ignition coil fuse and checked to see if the dash light for low coolant came on. Even with the fuse pulled, the light was still there. My thought was that if it was somehow connected to the ignition coil fuse, it would go out. Am I missing something? I am not an electrical genius so any thoughts would be appreciated. Thanks, Larry.

 

[luigisho]

I don't understand the question. Do you have a low coolant light on when the car is running? Have you checked the coolant level to see if it is indeed low? Wouldn't pulling a fuse to a system trigger a fault code by itself? Have you tried what was suggested above and unplug the sensor from the rest of the wiring harness and seeing if that has any effect on how it runs or fault codes?

 

[Larry Rivelli]

Hello,
Yes, the low coolant light is on when the car is running or the key is in the on position without the car running. Coolant level is good but the light still stays on. The sensor is shot and I have been unable to find anyone that makes a replacement. I do not have anything to check fault codes and am NOT an electrical genius. I did think that if the coolant sensor was the problem, it would have to be connected to the ignition coil circuit since that is the fuse that blows. So, I reasoned that if I pulled the ignition coil fuse, the low coolant light on the dash should go out. Did not happen. As far as how the car runs, no different with the light on or not. Still runs fine as long as the fuse is not blown, then it will not start or run at all. Hope that helps clarify what my problem is and what I was trying to accomplish by pulling the fuse and seeing if the low coolant light was still on. Hopefully, the wiring schematic ordered should be here in the next week. In the meantime, I carry a lot of extra 10 amp fuses. Thanks for all your help and thoughts. They are much appreciated. Larry

 

[luigisho]

Ok so I would do what was suggested several posts ago by Off Road SHO and unplug the coolant sensor from the wiring harness and see if that puts an end to the fuse blowing issue. I'm not sure about the light on the dash. Most sensors are linked to the PCM (computer) and if there is an indicator light it will not go out until the error in that chain is resolved. If you unplug a sensor generally that will set off a trouble code somewhere and an indicator light if that is a critical system like coolant, oil, etc. You may continue to see the coolant light with the sensor unplugged-- and still manage to resolve the fuse issue (or not). Worth trying first as it is easy and doesn't cost anything

 

[Larry Rivelli]

Thanks. That makes sense. I did not think about all the stuff that has to go through the computer and that the light might not be connected at all to the sensor directly, but the sensor going to the computer and then the computer lighting up the dash low coolant light. One of these days, I will have to remember the car has a computer. LOL. Thanks again for all the advice here. Larry