I have recently encountered an electrical gremlin that is about to drive me insane. After my truck (79 f100 351w duraspark) is warmed up and shut off it will not start again untill it cools off. I tried a new coil, and replaced the duraspark modual. The cap, rotor, and plugs are all new. The distributor is a few years old. Sometimes it will fire right up and other times it will just crank and no spark is visable when a plug wire is revoved. I 'll look for the problem and about the time I'm ready to call someone to pick me up it will start and run fine. It never dies while running. I think it may be in the wiring. When it won't start I've checked the and the coil has 12 volts when the key is on. I don't know what my readings should be elsewhere and any information on tracking this problem down would be greatly appreciated.

 

Hmm, seem like I tackled this situation at one time,
Do this, when the engine does not fire up, check if you are getting fuel and // or ignition coil spark.

 

It could be the pickup in your distributor. Sometimes when they go bad, they act flakey instead of just completely failing.

 

I had a similar problem, it ended up being the coil. The problem was I put a new coil in and had the same problems so I started looking elsewhere -- but what happened was the new coil didn't work either (Wells brand, from autozone, seems a lot of people were having problems with Wells ignition parts around the same time, now I avoid them). Once I replaced the "new" coil with a MSD coil it ran like a champ.

 

Start wiggling wires. Do a section at a time, turn the key.
If the wiring has the factory slip on connectors at the solonoid, crimp them a little with pliers. Give the one with the "I" special attention.

 

Vapor lock?

 

I'm going to try the pickup tonight. I think it is an ignition problem and not a fuel issue since I can see that there is no spark when it won't start.

 

I'd lean towards the coil also, even if it is new. And make sure they sold you the right coil. If it has an internal resistor it may not be getting enough juice to spark when it's hot. The previous owner of my 70 stang gave me that problem for free with the car.:-)

 

If no there is no spark, then it is going to definitely be an electrical problem.
It seems like the only part not replace is the pickup coil and would be a good part to test and replace if necessary this part.

this is a good resource page. http://www.therangerstation.com/tech_library/DurasparkII.html

Verify the red and white wires are getting positive "+" battery power.
The red wire will have positive "+" battery power with the key in the run position. The white wire will have positive "+" battery power with the key in the start postion and usually gets the power source from the starter solenoid.

One must not overlook the possibility of an electrical short. Common places for these electrical shorts or bad connections are as follows:

1. Check the connection at the coil.
2. wiggle the wire harness at the coil, while some one is trying to start your vehicle.
3. wiggle the wire harness at the distributor, while some one is trying to start your vehicle.
4. Wiggle the wire harness at the ignition module, while some one is trying to start your vehicle.

 

Check number one, check the wires and contact at the coil, then with an ohm meter, you can check the connection from the ignition module harness terminals to distibutor housing harness terminals, and coil wire terminal. Wiggle the wires while performing the test to verify if there is a short in the electrical system.

Check number two, Check the wires and contact at the ignition switch, then with an ohm meter, you can check the connection from the ignition module terminals to the ignition switch wire. Wiggle the wires while performing the test to verify if there is a short in the electrical system.

Refer to electrical schematic for wire colors and designation.



Other test and information found at: http://www.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/0a/50/6e/0900823d800a506e.jsp#hd1-1-6

http://www.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/0a/50/6e/0900823d800a506e.jsp
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Maybe try another ignition module? I had two sitting on my fender on a 86 f250. When one would act up, I switched to the other and it worked great until I had to switch it back a couple of months later.

 

I repaced the pickup, well the whole distributor since I'm at school and don't have a good place to disassemble it, tonight and it seems to be working after one trip. Thanks for all the input.

 

Okay Everyone !

Here is something that has happened to so many people and still never gets mentioned.

Check the ends of where these little wires attach.
ie: On the Coil,Distributor connectors

So many times they are hanging by a strand of wire because they have been bumped and corrode & eventually become a problem.

This is a real problem & becomes a headache to troubleshoot