Ok i have an ongoing issue with my truck. its an 84 f350 with the 7.5 gas engine. Starts just fine. but the issue is it engages the starter again while the engine is running. I have replaced the starter solenoid because i figured that was the issue. and now its doing it again. this time it will crank even with the key off and out of the ignition. I had to pull the negative battery cable to get it to stop. If i try to reconnect the cable the starter immediately starts to crank. That is until i smack the solenoid. then i can safely replace the battery cable. couple of things i checked. the s terminal cable has voltage if my brake pedal is pressed which is also when the starter engages when i am out driving. That cable should only have power when the ignition is in "start" correct? I am not sure where to start looking. I have read many posts about just replacing the solenoid which i will do again but that is just a symptom of another problem. and i cant find the solenoid i need at my local parts stores. they keep trying to sell me the one with short posts. i need a long post.

so any ideas on what to check for would be great. thank you in advance.

 

Clean up the ground connections at block, frame and firewall to bright shiny metal and tighten securely. I'd recommend a Motorcraft solenoid over the parts store replacements. Make sure the battery is charged up thoroughly.

 

ok update. first the parts are motorcraft. I already read all the issues with the off brands. second i can now start the truck with the brake pedal. i can turn the key to on and hit the brake pedal and the truck will start. so there has to be a wiring issue. also i have zero reverse lights. so i guess it is time to go wire hunting.

 

Evil, hope you have a Haynes /Chilton book handy. Yes, there is a wiring problem! Had any work done on the truck lately? Welding, auto work of any sorts and if not, some switches/Grounds that go bad , cause problems. Try and narrow it down before this started( Previous work). Have you miss wired something when working on it? Check all fuses, inside and out in engine bay. TR

 

ok reverse lights werent working because previous owner didnt put bulbs in the sockets. They are functioning properly now. However i can still start my truck by pressing the brake pedal. but only when the S wire is plugged in on the solenoid. and it stops if i disconnect the wire. then i can use the brake pedal as normal. I used this method for a while when i was driving the truck but i always thought it was the solenoid causing the issue. So now i am back to square one.

I bought the truck used about 2 years ago. i drove it for one year and then it was parked. The problem started about 3 months in after purchase. I quickly found that if i unplugged the s wire the truck would be ok to drive and function. i just had to plug it in to start the engine. I have done absolutely nothing to the truck since i got it besides replacing the battery and the solenoid. Both were after the problem started.

 

I say you will be doing some wire hunting!
I cant even start to guess where to look as I have never heard of this happening.

Good point on "did you have any work done before this started?". I see that is not the case

What trany do you have? Auto by any chance?
I ask because I am trying to see where the brake light wiring & starter wires could be next to each other. That may not be it either. Was thinking where the NSS & brake light wires could be next to each other on the frame rail but see below*.

Brake wiring(roughly): fuse> brake light switch> turn signal switch> to rear lights.
Does the starter work if you turn on the left OR right turn signals?
If not then my thinking the issue is between brake switch and turn switch, read under the dash. This is also where the starter wires would be.

*Where the wires go thru the fire wall the brake lights are already after the turn switch so if there the starter would work with left/right signal.

Just how I would try and get closer to where to look.
Dave ----


just a thought it is easy try and adjust the IGN switch. I wonder if it is off a little if some thing is back feeding thru?

 

I do have an auto trans. I just ran out to see if the turn signals start it and they do... o.O
how weird is that?

 

Both the left & right or just 1 side?


Let me think. (you smell something burning )
I think the NSS is on the side of the trany and plugs into the rear harness.
This rear harness I think also has a plug from the main harness to the rear on the engine bay side under the brake master top of frame rail.
I wonder if you were to unplug that connection and tried the brake/turn if it still starts?


You have a v8 did that plug/wires hit the exh Y pipe?
Dave ----

 

I only tried the left signal. i was working on figuring out the reverse lights earlier so i can say that the wires down there are ok and havent touched exhaust or anything. which plug should i unplug to see if it will start up? the one you are talking about under the brake master? or the one by the tranny.

 

Under the master.
I am trying to figure were to look for a short.
If it is unplugged and it will not start then it may be that rear harness but......
Being the NSS is now out of the picture could that be why it is not starting?

One way to see is to find the NSS wire pins and jump them at the truck side of the connector and hit the brake/sig. That I think would tell us if it is or is not the rear harness.
Dave ----

 

ok so jump the NSS connector with the key on and see if it starts the truck? its a 4 pin connector. which pins should i jump

 

There are quite a few plugs beneith the master. Are ya talking the huge one?

 

First I would just disconnect to plug under the master and see if it will start by the brake.
If so no need to go jumping anything as the issue is before that plug.
Either way the issue I am thinking is still before that plug.


I don't know what pins but here is my thinking "either way" is.
If you were to jump the pins and it did start by brake the short could be on the "after" wire of the NSS on the main harness.
So either way I am thinking it is in the main harness.
See what I am thinking here....if so please tell me
Dave ----

 

ok while i was waiting for your reply i unhooked the NSS connector and jumped the wires and the starter kicked on. so i am not sure what that says but its a start. So just to clarify i need to unplug the long rectangular harness that plugs into the firewall and try to start it with the brake pedal. correct?

 

found it.