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Truck just shuts off

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Old 10-28-2018, 11:44 AM
ford5o
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Truck just shuts off

I have a 77 ford cab on a 79 frame. Shouldn't matter but here i go....... Truck just shuts off, usally while sitting at a traffic light, sits and idles good but then light turns green to go and i give a rev before letting the clutch out and it shuts off. No spit spudder or anything, just shuts off like turning the key off. Now it wont even crank to try and start, keys on and radio still works, but wont crank. Sit for a minute( about) and it starts right up and continue on. I cant get it to happen when i want so i can check some things. This happened last friday coming home from work and i messed and looked at things all day satday, all was good and working well...... Drove it all week, 45mins to work 45mins home. Untill friday again, traffic light just shut down and wont crank to start. Sat for a minute or two and startec up and continued on, this time it shuts down again while driving. Push clutch in and roll, as rolling i pop the cluch back out and it starts and runs. I dont get it, my thoughts are, not bad starter or solenoid cause that woundnt shut it off, not distributor cause it should still crank and try to start. What do you think? O ya, also last winter when really cold it kinnda did the same. Cold morning, turn key to start and nothing, radio would come on when in run but attempt to start and nothing, wouldnt crank. Keep tryin and would start no problem. Once started had no problem..... Last year. Its a 79 4x4 150 with 4 speed with 351m.
 
  #2  
Old 10-28-2018, 12:03 PM
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Originally Posted by ford5o View Post
I have a 77 ford cab on a 79 frame. Shouldn't matter but here i go....... Truck just shuts off, usally while sitting at a traffic light, sits and idles good but then light turns green to go and i give a rev before letting the clutch out and it shuts off. No spit spudder or anything, just shuts off like turning the key off. Now it wont even crank to try and start, keys on and radio still works, but wont crank. Sit for a minute( about) and it starts right up and continue on. I cant get it to happen when i want so i can check some things. This happened last friday coming home from work and i messed and looked at things all day satday, all was good and working well...... Drove it all week, 45mins to work 45mins home. Untill friday again, traffic light just shut down and wont crank to start. Sat for a minute or two and startec up and continued on, this time it shuts down again while driving. Push clutch in and roll, as rolling i pop the cluch back out and it starts and runs. I dont get it, my thoughts are, not bad starter or solenoid cause that woundnt shut it off, not distributor cause it should still crank and try to start. What do you think? O ya, also last winter when really cold it kinnda did the same. Cold morning, turn key to start and nothing, radio would come on when in run but attempt to start and nothing, wouldnt crank. Keep tryin and would start no problem. Once started had no problem..... Last year
The 3 step scenario of a failing DuraSpark ignition module:

1) Module overheats, engine dies. Module cools down, engine restarts almost at once.

2) Module overheats, engine dies. Module cools down, engine restarts in an hour...or so.

3) Sooner or later, usually sooner, the module overheats, BURNS OUT. Now the engine will not restart.

Module located on the left fender inner apron, just in front of the firewall.

Engine heat, especially when radiating from the V8's red hot left exhaust manifold, is the mortal enemy of these modules.

Taking it to an auto parts store to be tested: Will test OK unless the little darlin' has burned out.

If replacing, use some washers to space it further away from the apron, the more airflow...the better.
 
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Old 10-28-2018, 12:41 PM
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Not disagreeing, but if the module was going bad wouldnt it still crank and try to start? And why now when outdoor temp has dropped.
 
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Old 10-28-2018, 12:58 PM
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Originally Posted by ford5o View Post
Not disagreeing, but if the module was going bad wouldnt it still crank and try to start? And why now when outdoor temp has dropped.
If the engine dies, then won't crank, you have another problem besides a failing module.

 
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Old 10-28-2018, 01:04 PM
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Thought so, kindda thinking igntion switch, key switch?
 
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Old 10-28-2018, 02:19 PM
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Just a thought. Since i did the cab swap about 8 years ago the heater box was also changed cause its a ac cab...... The one end duct is blowing almost straight onto the ignition key switch...... Can it be "overheating" and failing? First thing i do when it dies, turn off heat and turn down radio...... Hmmm.. Making a duct now
 
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Old 10-28-2018, 04:19 PM
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You probably already checked, but could it be a loose ground to the frame?
 
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Old 10-28-2018, 08:20 PM
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Maybe..... Thats a good thought, only ground i got is battery directly to the engine block, i will make some grounds from cab to frame and add battery to frame. Easy and cheap, wont hurt nothing to just do it
 
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Old 10-31-2018, 08:02 PM
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I was gonna ask same, update forum if that worked pls
 
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Old 11-03-2018, 12:46 PM
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Next time it does it, reach behind your ignition switch and try to push the wiring connector tightly towards the ignition switch while you try to start it. Those plastic wiring connectors get brittle over time and the "ears" that hold it to the switch may have broken off causing intermittent connection. Your ignition and battery feed go through that connector.
 
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Old 11-04-2018, 10:44 AM
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Making more grounds today and gonna drive it. Last time it sat for a week or so it was fine for about 2 weeks untill it started acting up again. I have messed with the plug into the ign key switch twice now while being dead and didnt make a difference, but i was thinking the same thing, so i got a back up. Easy enough to plug in on the side of the road if or when it shuts down
 
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Old 11-06-2018, 08:46 PM
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Day 3 with no problem and a tank of fuel (small tank, only 19 gal). About a 2hrs non stop and 4, 45 min cruises to work and home. In heavy rain and flooded roads also
 
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Old 11-19-2018, 09:21 PM
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Been running good for a week or so........ Untill tonight, sittn at traffic light idleing fine, light turns green, little rev to let cluch out and it shut off. Started right back up and drove home........ Wtf?





 
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Old 11-19-2018, 09:57 PM
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So, when this happens, you turn the key and nothing happens? The starter doesn't click or spin or a hum? Nothing?
 
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Old 11-21-2018, 12:35 AM
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What you described either the ignition switch or the starter solenoid. The S terminal on the solenoid should have 12 volts while cranking. The I terminal should have about 8 volts while the truck is running. Both voltages are dependent on a properly working ignition switch. Voltage on S while trying to start and nothing happens is likely a bad solenoid. No voltage on S is likely a bad switch.
 

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