Alright, I've got a '79 F150... it's a 2wd with a 400, C6 and AC... I had some starting issues related to the ignition switch.. I pulled the switch and rebuilt it (replaced the springs, cleaned the contacts, greased the bearing, etc...) I put it back together and it still won't turn over... I checked the solenoid and where the ignition goes into it there are two posts, both have leads on them... ie... there's the lead from the battery, then two little posts, then the lead to the starter motor, both of the two posts have leads goin to them.. I checked those posts with the key in the start possition and one has 7.5volts and the other is 0... then i checked them with the key in the on possition and the same result... anyone have a wiring diagram for my model with two leads to the solenoid.. I've never seen that before.

 

On the starter solenoid there are two big posts, one to battery positive, one to ground. The two little posts are marked S and I. S is starter and I is Ignition. The starter wire should be on S. At least thats the way its on my 400m.

 

One small lead should have a 'I' above it, this should be hot in the run position. The other lead should have a 'S' above it, this one should be hot in the start position. Use a jumper wire connected to the + battery and touch the other end to the 'S' terminal, the starter should crank. IF it does, the solinoid and starter are good and the problem is with the key switch or wiring between.

Marty

 

AH you may want to rewrite that, one of the big posts is "+" the other is"+" to the starter, NOT GROUND.

 

Okay guys this thread reads wierd.

The starter solenoid has four terminals on it.

Two large lugs on either side of it.

One has the starter cable attach to it.

The opposite lug gets the Positive cable from the battery attached to it.

there are also two little terminals on the solenoid ,they are the S & the I terminals.

The I terminal wire is part of the harness, this circuit is for 12v of current sent to the coil when the starter is engaged to help with better part to the plugs during start up.

The S terminal is for allowing small amount of current to actuate the switch that allows Large current to activate the starter through the ignition switch.


Once the starter isn't cranking,there shouldn't be any current at the S terminal.

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Now to resolve the problem.

Take a 12 gauge wire and attach it to the + battery post and touch the other end to the S terminal of the solenoid .

Does the starter crank ?

If not ,there is problem with starter or solenoid or the battery.

If battery is fully charged it shouldn't be the problem.

Now try attaching a booster cable from the + post of the battery to the starter cable lug,.
Does the starter crank ?

If not,the Problem is with the starter.

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Ignition switch !

Attach a test light to the wire going to the wire (only) that goes to the S terminal of the solenoid.

Turn the key to start .....Did the test light illuminate ?

If so, the ingition switch is fine.
If not, the switch is faulty


Here is your ignition system.
Although the relay shows only One small terminal,there should be two

http://www.clubfte.com/users/mil1ion/DurasparkII.JPG

 

Million, you forgot the neutral safety switch.

 

Yes I did ...damn !

although ....That is a concern from use of the key.

I was starting (pardon the pun) from the no crank condition

 

well I read up on the wiring diagram and I think it may be the neutral safety switch or a broken/grouned wire... The reason for this is because the battery has enough juice to run the lights and blower motor... Also, there is "click" at the solinoid... I think I tried to fix it by puting one of my spare solenoids on it too and that didn't fix it... this truck has been sitting a few months because I'm away at school and it quit working about the time I finished my Mustang. I'll mess around with it more when I get the chance but thanks for the replies...

 

If the solenoid clicks when you turn the key, your ignition switch and neutral safety switch are OK.

You say your battery is good. Next step is to clean your battery terminals really really well. Also, clean the cables. Both cables, both ends. The clean the cable that goes from the solenoid to the starter motor. Next clean the ground strap/cable that goes from engine to chassis. In all cases clean the surfaces that the cable ends attach to. Make SURE that your solinoid is grounded. Most likely it will start now if you are right about the battery being good. If not, use a jumper cable hooked up to the big terminal on the starter and touch it to the battery positive. If it cranks, replace the solinoid. If not, replace the starter.

 

Figured it out... two problems, one the battery cables had crappy ends on them, one was split, the other was the neutral safety switch... i moved the shifter around and put it into neutral and then it cranked over. IDK if there's a connection problem within the gear selector or if there is a problem with the neutral safety switch.

anyhow thanks alot.

 

You will need to readjust the NSS.


Let me know of you need to know the procedure for doing so.