73 F100 Ignition problems
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From: Wingo, Ky
73 F100 Ignition problems
My 73 F100(302) was running fine the other day, no problems starting or anything. It sat two days untill today. Went to start it and it would turn over and over but not start. I checked for fire and its not firing. What could happen the two days it sat?
I've told this before in other posts but........new wires, new plugs, new distributer cap, new points, new condensor.
I checked to make sure points were properly gapped and they were. While key is turned on if you stick a knife between the points they will fire. While the engine is turning over with the key there is no fire.
I replaced the coil and that didn't fix it. What else could it be? Bad distributer? Thanks in advance.
I've told this before in other posts but........new wires, new plugs, new distributer cap, new points, new condensor.
I checked to make sure points were properly gapped and they were. While key is turned on if you stick a knife between the points they will fire. While the engine is turning over with the key there is no fire.
I replaced the coil and that didn't fix it. What else could it be? Bad distributer? Thanks in advance.
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From: Wingo, Ky
Tomorow I was going to do the checks for the coil that are in my haynes manual. But then I thought, If I can make the points spark with a knife don't that mean the coil is getting power to it and is working?
The manual says with the key on check for 12volts at the positive coil connector terminal. I plan on doing that anyway. It says if there is no power to check a fuse and other things. What fuse?
It says if there is power at the coil check for power between the coil negative terminal and ground. So I would place my light on the negative terminal and the light wire to ground?
If all this checks good I suspect something to do with the plate inside the distributer? Grounding out? Condensor wire and coil wire(primary lead) that goes to points arm touching something it shouldnt? Are the condensor wire and coil wire supposed to be touching each other when connected to points or should they be separated?
The manual says with the key on check for 12volts at the positive coil connector terminal. I plan on doing that anyway. It says if there is no power to check a fuse and other things. What fuse?
It says if there is power at the coil check for power between the coil negative terminal and ground. So I would place my light on the negative terminal and the light wire to ground?
If all this checks good I suspect something to do with the plate inside the distributer? Grounding out? Condensor wire and coil wire(primary lead) that goes to points arm touching something it shouldnt? Are the condensor wire and coil wire supposed to be touching each other when connected to points or should they be separated?
Hotshot
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From: Stanley, VA
If you can get it to fire by manually grounding the points then the coil, condenser and wires are good. A couple of things to check. You said "new points", did it have the new points in it before it quit or did you change them after it wouldn't start? Either way, I would clean the points. Run a very fine sandpaper or emery cloth between the contacts to clean them. Then run a lint free cloth to get rid of any grit that may be left (a dollar bill is ideal for this).
If this doesn't work, check the small ground wire in the base of the distributor. It will go from one of the screws that holds the points down to another screw in the distributor base plate. See if it's broken or not hooked up. Clean the connections at both ends and check for spark.
If these ideas don't work. check the dist. base plate itself. It's a two piece deal that rides on three little plastic buttons. One part pivots on the other to work the vacuum advance, They were notorious for going bad.
If this doesn't work, check the small ground wire in the base of the distributor. It will go from one of the screws that holds the points down to another screw in the distributor base plate. See if it's broken or not hooked up. Clean the connections at both ends and check for spark.
If these ideas don't work. check the dist. base plate itself. It's a two piece deal that rides on three little plastic buttons. One part pivots on the other to work the vacuum advance, They were notorious for going bad.
MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
You need to try the test that Josh mentioned. Ground the test light on the engine with the light powered from the terminal he has specified. A points coil may not have TACH TEST labeled, in which case you'd just use the negative terminal (same thing). Crank the motor over using the key.
The points sparking doesn't tell you anything useful. It's a good sign (you have at least some power to the coil and your coil primary isn't open-circuit) but it doesn't quantify anything. Start with the blinking light test and we will go from there. Breaker-points are very simple to diagnose.
The points sparking doesn't tell you anything useful. It's a good sign (you have at least some power to the coil and your coil primary isn't open-circuit) but it doesn't quantify anything. Start with the blinking light test and we will go from there. Breaker-points are very simple to diagnose.
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From: Wingo, Ky
Can I do the blinking test with the key on then jump it across the selinoid? I will be by myself. Yes it has run before with all the new parts listed above.
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No, this will test your ignition switch and the solenoid.
With a test light that has aligator clips you should be able to position the test light and be able to be in the truck while starting and still see it. Either by looking thru the gap in the opened hood or reaching into the truck to start it and leaning out to see past the hood. Don't sweat it, sounds harder than it really is.
Josh
With a test light that has aligator clips you should be able to position the test light and be able to be in the truck while starting and still see it. Either by looking thru the gap in the opened hood or reaching into the truck to start it and leaning out to see past the hood. Don't sweat it, sounds harder than it really is.
Josh
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From: Wingo, Ky
With key on I have power going to coil and power coming out of coil. I assume the red/green wire is positive and the black wire is ground?
While holding the test light on the negative coil terminal and making sure it is getting good contact I had a friend turn the truck over. The light did not blink, it was just constant light.
I guess the coil is ruled out and I can take the new one back so I can buy something else.
While holding the test light on the negative coil terminal and making sure it is getting good contact I had a friend turn the truck over. The light did not blink, it was just constant light.
I guess the coil is ruled out and I can take the new one back so I can buy something else.
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Now test your distributor pick-up, Test with an OHM meter the orange and purple wires going into the distributor... should read between 400-800 ohms, most read around 700.
Since the light didn't blink while cranking the pick-up in the distributor isn't working correctly.
Josh
Since the light didn't blink while cranking the pick-up in the distributor isn't working correctly.
Josh
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Oops, guess I should keep up on this stuff.
Well, points are just a mechanical version of the electronic pick-up module.
Now, you have a situation where the points are not opening and more importantly NOT CLOSING.
It is possible to adjust the points to where they are always open. Are you certain they are closing on the FLATS of the dizzy cam?
Josh
Well, points are just a mechanical version of the electronic pick-up module.
Now, you have a situation where the points are not opening and more importantly NOT CLOSING.
It is possible to adjust the points to where they are always open. Are you certain they are closing on the FLATS of the dizzy cam?
Josh
MSEE
Joined: Apr 2004
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From: Austin, TX
Two other things to check:
1. Pull the distributor cap off and crank the motor over, and make sure the rotor is actually turning.
2. Test for continuity from the base of the points to engine ground. There is a small ground strap that jumps the breakerplate to the baseplate inside the distributor. If it frays, the points cannot ground. The points closing (and grounding) is what should make the test light turn off. The light comes back on when the points open up and open-circuit the coil primary winding. This should happen over and over as the motor cranks, hence the blinking action.
1. Pull the distributor cap off and crank the motor over, and make sure the rotor is actually turning.
2. Test for continuity from the base of the points to engine ground. There is a small ground strap that jumps the breakerplate to the baseplate inside the distributor. If it frays, the points cannot ground. The points closing (and grounding) is what should make the test light turn off. The light comes back on when the points open up and open-circuit the coil primary winding. This should happen over and over as the motor cranks, hence the blinking action.
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From: Wingo, Ky
Well I went back down to the truck this afternoon. I jiggled around the dizzy plate and lo and behold it fired up and ran. So I guess I need to replace it, is it difficult to remove it and put in the new one? I have a slight miss at idle I figure it is related to that plate.
The gas in the truck is very old. I put some new in it but it still smells like rotten eggs running and it smokes some. Ocasionally it smells like oil smoke but I don't see any on the plugs. Im sure the valve seals are probably bad though since it has mostly sat the last 20 years until I got it.
Sorry pic is blurry. But it shows the engine is running clean. I drove it up and down the road a few times then let it sit and idle for a while, pulled plugs out and they looked like this, all of them.
The gas in the truck is very old. I put some new in it but it still smells like rotten eggs running and it smokes some. Ocasionally it smells like oil smoke but I don't see any on the plugs. Im sure the valve seals are probably bad though since it has mostly sat the last 20 years until I got it.
Sorry pic is blurry. But it shows the engine is running clean. I drove it up and down the road a few times then let it sit and idle for a while, pulled plugs out and they looked like this, all of them.
MSEE
Joined: Apr 2004
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From: Austin, TX
I'd find out what specifically is loose in the distributor before spending some $50-100 on an entire replacement. There's not much in there that can't be replaced on its own. The baseplate/breakerplate combo is about the biggest thing in there and can be replaced for under $15 and it's only held in by 2 screws.