fmc400 has been helping me with this problem through a pm but he is either away or extremely busy, so I am reaching out to others. I bought a truck from an elderly gentleman last week. 1973 302 automatic. He said he parked it 4 years ago and it was running. We could not get it to turn over when I bought it. I brought it home and changed the fuel. I cleaned up the battery, starter, solenoid, and battery ground terminals. I tried to start it with a charged battery but nothing happened. fmc400 took over here. He and his posts got me to where the engine is turning over but has no spark. I checked spark with a screwdriver at both the coil wire to the distributer and in a spark plug wire both next to the block. No spark. The distributer is spinning. I did a "tach test " on the coil and it is positive. The test light blinks as it should. Here is where I get lost on my next step and what I should check. One other note, I cannot find the ignition module and I do not see any cut wires where it would have gone. Thank You.

 

Sorry, I've been away with my hands in all sorts of other projects.

If a test light between the negative terminal of the coil and ground BLINKS as the engine cranks, then the entire primary side of the ignition system (including the ignition module) is fine.

Your description indicates the module is switching the coil, yet there is no spark. If those results are real, then that indicates the problem is in the plug wires, cap/rotor, or secondary winding of the ignition coil.

 

Thank you, i just finished reading a past thread in which you supplied information and I learned that the primary side is functioning fine as you say. If it is the secondary components are the problem, why can't I determine why spark or power is not coming out of the wire that leads to the distributer. Also, why do I not see an ignition module in this truck like I do in my daughters 75 truck. Is this truck called a Duraspark ignition?

 

If it is a 73, it will have points. 1974 was the first year of electronic ignition. That would explain why you can't find the module.

 

Don is correct; you have points instead of Duraspark. However, the coil BLINK test you performed works just the same. It doesn't change anything for these purposes.

 

Don and fmc400. thanks for the help. So the problem is in the plug wires, cap/rotor, or secondary winding of the ignition coil. I will read on the site how to narrow it down. I will start in logical order. So, is there a test to see if the wire from the coil has spark or power (not sure of the correct term). What is the secondary winding of the ignition coil?

 

You said "I checked spark with a screwdriver at both the coil wire to the distributor and in a spark plug wire both next to the block. No spark" Considering all the other tests you have done it sure sounds like you have a bad coil. You should still probably replace the plug wires, cap and rotor if they have any age on them.

 

Thanks for the help. I will do so and report back.

 

I went out this morning questioning whey the coil could pass the "tach test" but not have spark or power at the wire going into the distributor. So I turned over the engine a few different times with the coil wire near a grounding point. The first time I got a spark. Just one. I tried again a few more times and got some intermittent spark. One time I got none. So in keeping with fmc400 rule of not buying parts without a logical explanation, is it fair to assume that the coil is bad? Canus has suggested to replace and I guess that's what I should do. Also, the accelerator pump diaphragm is leaking and I should replace this as gas is spilling onto the manifold. My carburetor tag reads D3TF NA Motorcraft. I cannot find on line if it is a model 2100 or 2150. Can I get some help on this? Thanks

 

You can easily check the secondary winding resistance of the coil with a multimeter. The resistance between the large output post and either of the small posts should be between 7 and 10 Kohms or so. I would be tempted to believe the intermittent spark you're seeing is a result of the test procedure rather than a faulty coil. Personally I'd spend the money on a spark tester instead of a coil.

If the choke pulloff is mounted vertically on the air horn, it's a 2100. If it's mounted horizontally on the passenger side of the throttle body, it's a 2150.

 

I read a post from you earlier this morning on checking the coil. It must be removed though and is it a good test? I have read that it may not be a true test (don't know where I read that). Set the meter to ohms at the 2 k, 20k, 200k, 2m, 20m? sorry not knowledgeable, but trying. Thanks

 

The coil doesn't have to physically be removed from the engine, but all leads do need to be disconnected. Set the meter to the 20k setting for the secondary winding.

It's true that a DC resistance test does not exhaustively check the coil. A true test is to "ring" it using a high-voltage oscilloscope probe. However, the most common failure of ignition coils is shorted or open windings, which would be revealed through a resistance check.

 

I have two coils. one that was in the truck and a spare that came with it. I have tested both. I have disconnected all wires for the test. Neither coil register any ohms when I connect the two outside terminals. When I test from the center post to either of the outside terminals on the one in the truck, I get a 6.78 reading. When I check the spare, I get 9.47.

I think I am buying a coil, right?

I am also going to buy a spark tester. will a spark tester adapt to the wire from the output of the coil so I can start from there?

I am trying to determine the correct carb and tried to post pictures but was not successful. I can say that it looks like the one in the ford truck shop manuel for 1977 on page 24-25-5 (even though its a 73) less the choke pull down assembly apparatus. Does this help?

Thanks for the help.

 

That's because your meter is set to the 20K range. If you lower the range you'll see something between 1 and 2. The primary winding is much lower resistance.

The one in the truck is on the low side, but probably not enough to keep the engine from starting. You should replace it nonetheless.

Some are that way; others are installed inline with a spark plug. The instructions should describe how to connect it.

 

We are getting somewhere. I replaced the coil and I get the engine running. I am jumping it from the solenoid. if I take the jump off of the solenoid. The struck stops running. This is getting rewarding.