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  #1  
Old 07-30-2007, 09:48 PM
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quantalimo quantalimo is offline
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78 F150 wont start

I replaced ignition switch and selonoid .....I turn key to start i get nothing not even a click from the selonoid....

When i jump the hot wire to the (S) on selonoid engine starts but starter stays cranking then if i jump hot wire directly to starter it starts then shuts off when i disengage


there are four connections on selonoid what is the "s" for and what is the "I" for on the small wires................. other is + to battery and other is to starter


Help me understand a way to fix this problem
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Old 07-30-2007, 10:41 PM
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It is very simple. The "S" simply means start or solenoid. 12 volts from the ignition switch goes to here. When you turn the ignition switch to start it puts 12 volts onto this terminal and activates the solenoid. The "I" simply means ignition. This puts 12 volts into the ignition coil while the solenoid is activated.

You need to go to the top of this forum and read the first post titled Read Me First. Thats what it means, there is a lot of useful information there and it tells you how to get wiring diagrams so that you can trouble shoot this problem. You obviously don't have voltage from the ignition switch going anywhere. You need to get a wiring diagram to properly troubleshoot this problem. mil1on has a simplified one that is easy to understand. I will see if I can find it and post the link to it.
Here is the link.
http://www.ford-trucks.com/user_gall...photoid=113815
Here is another good diagram, http://www.clubfte.com/users/mil1io...itionSystem.JPG
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Last edited by fasthauler; 07-30-2007 at 11:13 PM.
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Old 07-30-2007, 10:57 PM
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IF it does Nothing when you try and start it, it sounds like it could be the NSS.

Try starting the truck at night with the lights on. IF they get dim then it could be a couple problems, but if they don't do anything, and stay just as bright, then try playing with the column linkage(put it in ALL positions, Park shove it all the way, put it all the way to 1st) and the whole time have the key in the start position. IF it trys to start or does start it is the Neutral Saftey Switch. Tighten the bolts on it, b/c they are the grounds, and that'd fix the problem.

The NSS is on the drivers side of the transmission about right in the middle of the drivers door. You might have to play with the posistion and tighten it up till you can start it with the gear selector in Park and Neutral.

Good luck
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Old 07-30-2007, 11:10 PM
Mil1ion Mil1ion is offline
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The NSS on a 78 is down at the transmission.

There is a plug on the firewall that you can bypass the NSS with a jumper wire.
see the grey connector above the valve cover on the left.




If it starts with the key with a jumper wire attached the problem is the NSS.
They get really greasy and grimey and fail.





Last edited by Mil1ion; 07-30-2007 at 11:17 PM.
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Old 07-30-2007, 11:16 PM
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Man you have great diagrams Dennis. This guy also posted this in the electrical forum.
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Old 07-30-2007, 11:24 PM
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MBB your So right

Thanks for the pictures Million...

Its is the neutral safety switch ; However when I start the the truck (in neutral) the "starter keeps cranking when engine starts" and "doesent stop cranking"....Could the NSS do this as well?..(Seems like a stuck selonoid but ive replaced it and still does same thing so whats going on?

Last edited by quantalimo; 07-30-2007 at 11:30 PM.
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Old 07-30-2007, 11:31 PM
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I'm not completly sure on that one. Every now and then mine 77 does that, so I turn it off, and start it again, and it doesn't do it after that, but I have a feeling it has something to do with the ignition switch.?.
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Old 07-30-2007, 11:39 PM
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Usually this is a result of a low battery start condition gone bad.

The Relay require LOTS of energy to click the points on and off to allow power to run to the starter cable.

If a low battery start was tried...the points weld together... to which when a freshly charged battery is installed it creates a direct non-stop start condition when the key turns to start.
Either you have a bad switch or a bad starter solenoid.

Try turning the key to RUN ..then use a jumper wire at the solenoid to trip the relay to crank the starter.

as Shown in GREEN text in Illustration above
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Old 07-31-2007, 12:13 AM
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Its solved

I did the green jump and starter stayed cranking while engine was running......I bypassed the starter safty switch and now it is back to normal. Therefore the neutral safety switch was causing the starter to stay on and running...But Thanks for the picture to find the bypass plug and thanks for all the NSS info very helpfull I posted at 9:48 pm and we collectively got truck running by 12pm about 2 hours...Thats awesome....and thanks again And its really cool too see post end up in success

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There is the plug that i put jumper in.....


Why I think this happened?

I wanted to change my transmission fluid and I pressure washed the grime and gunk off the transmission today and low and behold that grime was probably holding the NSS together LOL.....So leave that gunk on there save you some trouble........

Last edited by quantalimo; 07-31-2007 at 12:56 AM.
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Old 07-31-2007, 12:01 PM
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Since you got it going this is just a heads up. My wife's T-Bird was leaking tranny fluid bad from the shift lever. I just kept putting off replacing the seal and put a drain pan under the car. It was easier than getting the tranny apart. One day the starter stuck and just kept running. The voltage leak from the backup light across a very fluid saturated NSS switch was enough to hold the solenoid in after it was activated. This happened about four times and once in a very embarrassing situation. This is when I finally decided to drop the pan and replace that seal. I guess all of that free running on the starter caused its demise. One day it locked up again I ran out and pulled the "S" wire off of the solenoid. The starter just kept running. The solenoid was stuck. I replaced the solenoid and it ran fine for a couple of days and the problem started all over again. I replaced the solenoid again and it immediately fused again. After two more solenoids sticking immediately I finally decided I had a problem. I went down and got a new starter and solenoid and put them on. it has been over a year and still no problems.

The moral of the story is the starter can draw enough current to fuse a solenoid and still crank and the most important lesson is to fix a leak before it causes you more work.
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Last edited by fasthauler; 07-31-2007 at 12:04 PM.
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  #11  
Old 07-31-2007, 08:02 PM
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sounds like my problem

I have no leaks of oil or transmission fluid..I presussure washed tranny (so that i can work on it; was loaded with grimey mud almost like a tar) which may have caused the eletrical problem..But i am dropping pan to change fluid, filter and add a drain plug anyway..What else can I do while im up in there....
perhaps replace the seal anyway..Its old

Hard to believe all that stuff is so sensitive....

Also when the starter stuck and stayed stuck when i pulled off (s) wire as well..Before i resolved the issue...

Last edited by quantalimo; 07-31-2007 at 08:35 PM.
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  #12  
Old 08-01-2007, 01:40 AM
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I wouldn't bother changing the seals unless they are leaking.

I just wanted to give you a heads up on some of the problems that I had so that you won't have to struggle like I did if you ever have the same problems. And yes if the starter keeps cranking when the "S" wire is removed from the solenoid then the solenoid is stuck closed. This is usually caused buy an arc across the solenoid contacts. A starter drawing way to much current can cause this.
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Old 08-12-2007, 09:21 PM
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starts up again

The starter is sticking again ..........or shoud i say the selinoid is stuck it seems ........think the relay is getting welded shut by the current ........

I replaced it again it seems fine again for now............
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Old 08-12-2007, 11:09 PM
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It's a good possibility that the starter is drawing so much current that it is fusing the solenoid contacts. I know that is what happened to my wifes T-Bird. I fused 3 solenoids in one day and replaced the starter and never had a problem again.
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Old 08-13-2007, 11:25 AM
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one of my trucks has corrosion at the s terminal. if it won't start i twist the terminal and she starts right up. try that one out.
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Old 08-13-2007, 11:25 AM
 
 
 
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