just shuts down
Cranky Old Guy
Joined: Mar 2008
Posts: 3,562
Likes: 6
From: Raphine, Virginia
Bad part is he has cut the plugs out and hardwired. A good time to check that pickup module is when his system actually fails and then check the readings to see if they still fall within the parameters. Not an easy thing to do on the side of the road with his arrangment.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Bad part is he has cut the plugs out and hardwired. A good time to check that pickup module is when his system actually fails and then check the readings to see if they still fall within the parameters. Not an easy thing to do on the side of the road with his arrangment.
New User
Joined: Mar 2010
Posts: 9
Likes: 0
Have you checked the pickup module in the distributor yet? You're not looking at significant root causes. 99% of the time, when the ignition simply cuts off, the issue is the ignition module, or the pickup module. They get too hot, and they fail. The ignition module has a little harder time surviving because the case design is not heat sunk properly. The pickup module just gets old after 30 years.
You need to perform the resistance check per gfw1985's outline. This test will eliminate any catastrophic failues, like an open or short. Note, however, that the Hall effect sensor in the module is an active circuit element, so a resistance check won't tell you anything about it's functionality - so it's possible that it will ohm out fine, but still not work properly. Especially if the failure is heat-related, which is the case 99% of the time. In other words, if it passes the resistance check, it still doesn't eliminate the pickup module. However, I absolutely hate recommending to replace something unless there is hard evidence (that you can measure with numbers) that it has failed - unfortunately it's not possible to get that confidence with the pickup module, using standard tools.
Why do you suspect the ballast resistor? It's very easy to focus on items that look mysterious, or are easy to access under the hood - but proper diagnostic procedures and the process of elimination under the guidance of others are the key to solving any problem. The ballast resistor is just that - it's a specially doped wire that builds up resistance over its length. It's simply a kludgy way to reduce the coil primary current, which takes some of the load off the power transistor in the ignition module (or the points, before breakerless ignition). One advantage to making it a wire (as opposed to a single element, like in some Chrysler applications) is because it spreads the heat out over a long length, instead of focusing it on one single piece. The only way it can really go bad is if someone fuses it out by trying to wire loads off the coil positive terminal. The term "ballast" refers to many different applications - when used here, it simply acts as a fixed resistor.
You need to perform the resistance check per gfw1985's outline. This test will eliminate any catastrophic failues, like an open or short. Note, however, that the Hall effect sensor in the module is an active circuit element, so a resistance check won't tell you anything about it's functionality - so it's possible that it will ohm out fine, but still not work properly. Especially if the failure is heat-related, which is the case 99% of the time. In other words, if it passes the resistance check, it still doesn't eliminate the pickup module. However, I absolutely hate recommending to replace something unless there is hard evidence (that you can measure with numbers) that it has failed - unfortunately it's not possible to get that confidence with the pickup module, using standard tools.
Why do you suspect the ballast resistor? It's very easy to focus on items that look mysterious, or are easy to access under the hood - but proper diagnostic procedures and the process of elimination under the guidance of others are the key to solving any problem. The ballast resistor is just that - it's a specially doped wire that builds up resistance over its length. It's simply a kludgy way to reduce the coil primary current, which takes some of the load off the power transistor in the ignition module (or the points, before breakerless ignition). One advantage to making it a wire (as opposed to a single element, like in some Chrysler applications) is because it spreads the heat out over a long length, instead of focusing it on one single piece. The only way it can really go bad is if someone fuses it out by trying to wire loads off the coil positive terminal. The term "ballast" refers to many different applications - when used here, it simply acts as a fixed resistor.
Senior User
Joined: Jun 2011
Posts: 146
Likes: 0
From: Bristow, VA
Does this happen all times of the day or mostly at night. If this occuse at night , one of the things that could cause your truck to stall is that your alternator cuts out on you. Too much draw on power with the battery supply deplating quicker that the alt can resupply. This could happen during the day, but only if you have A/C in use. Also d you smell any gas when the truck stalls, could be a fuel pump failing or simply fuel related, I used to have my truck fail when I went up step hills and was baffled, then I chnged out my fuel filter and problem resolved. Probubly not these thing, but I want you to stay open to other posibilities.
New User
Joined: Mar 2010
Posts: 9
Likes: 0
Bad part is he has cut the plugs out and hardwired. A good time to check that pickup module is when his system actually fails and then check the readings to see if they still fall within the parameters. Not an easy thing to do on the side of the road with his arrangment.
Senior User
Joined: Jun 2011
Posts: 146
Likes: 0
From: Bristow, VA
A buddy of mine went to the store to get a coil for his 48 Ford Super delux and they gave hime a coil for a 12V ijnstead of 6V, are you sure you have the right coil? Sorry if the questions sound condisending, but not sure what your background is.
Cranky Old Guy
Joined: Mar 2008
Posts: 3,562
Likes: 6
From: Raphine, Virginia
i can appreciate what you're saying. but it appeared that the plugs where bad, hard wiring eliminated a problem,but not the root cause. it was an experiment to appease a colleague. and like i said i have a few modules,new and old, and the end result is always the same. i refuse to believe that module is to blame. it starts runs and dies,with a new module and with 2 other modules. like i said before it appears the coil is cutting out when it gets hot, but i have 3 coils and the result is constant, after about 25 minutes the truck dies, no spark. if i put a testlight to the tach side and crank, i get nothing til the end of the crank cycle. after an hour or so, she'll recover and while cranking i get 8-9 volts flashing on the tach side. so ,if i'm making any sence at all i believe it must be wiring...
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MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
I'm not sure what else to tell you - you've tried replacing the ignition module and the coil with spares, only to get the same results. You're wasting your time with spare ignition modules and coils. Your test light experiment proves that your ignition module isn't even switching the coil in the first place in the failure condition, and all signs point to it not even getting a trigger signal to begin with. Your focus needs to be the pickup module in the distributor; I'm not sure how to push you in the right direction any further.
New User
Joined: Mar 2010
Posts: 9
Likes: 0
Are you trying to imply that the help you have received thus far does not count as real insight?
I'm not sure what else to tell you - you've tried replacing the ignition module and the coil with spares, only to get the same results. You're wasting your time with spare ignition modules and coils. Your test light experiment proves that your ignition module isn't even switching the coil in the first place in the failure condition, and all signs point to it not even getting a trigger signal to begin with. Your focus needs to be the pickup module in the distributor; I'm not sure how to push you in the right direction any further.
I'm not sure what else to tell you - you've tried replacing the ignition module and the coil with spares, only to get the same results. You're wasting your time with spare ignition modules and coils. Your test light experiment proves that your ignition module isn't even switching the coil in the first place in the failure condition, and all signs point to it not even getting a trigger signal to begin with. Your focus needs to be the pickup module in the distributor; I'm not sure how to push you in the right direction any further.
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