My truck has now developed a coil problem.The truck is a 1980 Ford F100 with 4.9,but I doubt that helps much.The other day I hopped in it and was testing the turn signal indicators since I had just replaced the bulbs.When I turned on the left turn signal,I noticed there was a clicking/buzzing sound coming from the engine compartment.And no,it isn't the sound the blinker makes.So I pop open the hood and look at the wiring harness where the left turn signal bulb is.I don't see anything wrong,and the noise doesn't seem to be coming from there.I look to the left and I notice a white spark coming from around the coil.Upon closer inspection,I notice the spark is coming from one of the pins on top of the coil.This is also where the sound is coming from.One thing I know is that the previous owner redid the two coil wires himself,so some of the wire is not covered by insulation.But i've had the truck for a year now and never had a problem with that.So why is it doing this now?Any and all help is appreciated.If it helps,I can get a pic of the previous owner's wiring job.Thanks.

 

You get a spark at the coil only when the turnsignals are turned on? If so, most all weird problems like that are caused by wiring errors, or in the case of a truck that has not been messed with, grounding problems. Make sure you have a small wire running from the engine block to the firewall.

 

Yep.But it's not an ignition spark.It's on one of the two small wires on either side of the coil plug wire that goes to the distributor.And it doesn't seem to do it when the door is closed.Which I find strange.The truck does not seem to have a small ground wire leading to the Firewall.However,the previous owner tried to play electrician with the truck many times,so it is possible that the wire was cut.There is a small red wire next to the dizzy that comes out of the wiring harness that is cut at the end.Maybe this is the ground?And another thing,as aforementioned,i've had this truck for a year,just as it is,and have never had a problem with this.I haven't touched any of the wiring in the engine compartment.Thanks for the help.

 

I'm with Franklin, wierd stuff like that is often a bad ground

 

Yea,but if it was a bad ground,it should've been happening for as long as i've owned the truck.Right?

Does anybody have some type of electrical diagram of this ground?Or maybe somebody can get me a pic of there ground on there 300?All help is greatly appreciated.I'm trying to get this fixed before I shock myself. <table width="100%" align="right"><tbody><tr><td align="left">
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the whole chassie is ground.i would clean all your conections that go to the engine block,frame,and body.clean the rust and paint and wire ends.put dieletric grease and tighten.should cure your ground issues.bad grounds can cause lots of head scratching problems,create heat and burn electronics out. been there done that. good luck

 

Yes, the body grounds go through rusty body bolts and such. You definitely have a good ground to the engine block, because the starter works. But the engine and tranny are mounted in rubber engine mounts, as well as the body to the frame is mounted in rubber, so little ground straps are required to get good grounds to these components. Instead of troubleshooting grounding problems, it's often simpler to just add little ground wires, making sure you scrape the paint away from under the bolts.

 

forgot that, thanks franklin2

 

The Firewall to Engine block ground isn't all that small. It's actually a battery cable sized cable. I'll see if I have a pic.

Edit: I do not have a picture avaliable. (I can scan one possibly tomorrow)

If the horseshoe connector is missing from your wiring harness, (which seems likely by discription), you can get a replacement connector, that you splice in.

The turn signals and Coil hot wire are connected and fed from the same power source. The Ignition switch.

 

I actually did that when I replaced the alternator.

I looked all over the firewall,and I couldn't find any cable that size.There is a cable that size connecting the frame to the core support,but that's all.

Another question,it seems this problem has just started recently.I've had the truck for a year and never had this type of problem.Can you get a bad ground just out of the blue?Thanks for the help ya'll.

 

Can you get a bad ground just out of the blue?Thanks

yes you can... electrical problems dont give any warning as to when they will strike

 

yes it can happen,corosion or bolts get loose.like 81-f-150 said there should be a big wire from the negative side of the battery to the engine some where,if it's missing it's been using all the other grounds throughout the chassis.

 

The negative battery cable leads right to the support where the a/c compressor should bolt too if my truck had a/c.The cable is bolted to one of the holes.I've already cleaned this a thousand times.

 

is it arching at the negative side of the coil.DC volts arcs bad. try cleaning the coil body,mounting bracket and where it bolts to the engine.if the ground is bad it could have arched creating a higher resistance until it found another source to find it's ground. always remember electricty is lazy, it looks for the shortest and easyest route.

 

I really don't know where the negative and positive side of the coil is (sounds stupid but i'm only 16).It's doing it on the side closer to the firewall.I know that I had a valve cover leak,so maybe I got oil on the wires or the coil?I'll go out there tomorrow and clean it all off and see what happens.And come to think of it,it does kinda seem like it's arcing.Thanks for all the help ya'll.I'll post up the results tomorrow.