Help with no start + mystery wire

[dan84svo]

So I am now at a sticking point. Issue is that when ignition is turned to start position, buzzer sounds, brake and overboost light on dash illuminate, but no engine turn over. Starter tested good. Replaced the starter solenoid because it was easy and cheap enough. In the course of things, I found a single yellow wire in a cloth cover. It had a stripped end, and was fashioned into a loop and should obviously be attached to something, but I am not sure what. When this yellow wire is hooked to 12v, a relay sound can be heard. Before I change the ignition switch, I figured I would pick the brains of the group as to how to proceed. Here is a picture of the mystery yellow wire.
6296

[Ford Builder]

I wonder if its your clutch dump switch that's giving your problem; could be intermittent .

[MikeFleming]

With that outer shield on it, that looks like the wire that should go to the Coolant Temp (CT) sensor under the manifold. This will have no effect on your no-crank condition.

BTW - if you find a wire that you don;t know what it is, DO NOT connect it to power or ground. Your wallet will seriously thank you.

Your no-crank condition sounds like either the ignition switch or the clutch interlock switch (as mentioned above) - or both. You can easily run a jumper between the battery positive term in the starter solenoid and the start cable on the same solenoid to see if it engages the starter motor. Pull off the push-on wire that goes to the small stud on the solenoid and run a jumper from the battery positive term to the exposed stud. That will verify the starter motor and associated power (and ground) wiring.

Make sure it's out of gear before doing the above.

[dan84svo]

Okay, I did get it to crank by jumping the solenoid with a screwdriver, but I had a moment of terror because it kept cranking with the screwdriver off (key was on). Quickly pulled the negative cable, and let it sit for a little bit. Tapped the solenoid with the screwdriver, crossed my fingers and put the negative back on, and it didn't start cranking again (thank goodness). During all the excitement, the engine didn't fire while it was cranking. I changed the ignition switch thinking that caused the run-on starter condition and that didn't make it crank over. I pulled the plug from the clutch interlock switch and ran a jumper wire across the 2 terminals, and still nothing. I am going to check the coolant temp sender to see if that's the mystery wire, I need to quit on a high note. I am going to await further suggestions at this point. *** You were right about the mystery wire, Mike, I am going to have to put a push-on end on that wire or get a small nut and washer. Thanks!!

[MikeFleming]

*** You were right about the mystery wire, Mike, I am going to have to put a push-on end on that wire or get a small nut and washer. Thanks!! I was right!!

Someone make a note of his.

[dagenham]

When you turn the key on, do you hear the fuel pump prime???
I would think if it is priming then you at least have current throughout the car.

[dan84svo]

Yes, fuel pump primes, fan, lights, power windows/locks, accessories all work as they should. Amp and fasten belt warning lights come on, and then the brake and overboost light come on when the key is turned to the start position. Starter obviously does work (see above terrifying moment earlier) but not with the key. I am stumped as to what to check next

[in2fords]

Scince I made my own harness Im not sure how the stock spout wire looks, could that be the inline spout wire? any other torn up wires in there?

[k98dave]

"I am stumped as to what to check next"

Check the harness coming from the trans into the car. I had this disconnected when I replaced a clutch and forgot to reconnect it and had the same problem. Not sure why it would not crank but when I reconnected it everything was OK.

[SnakePlisskin]

You need to see if you have power at the solenoid push on wire, that wire comes from the ignition switch and should only be hot when starting the car. Do you have a test light and a person to assist you? You can do it alone, but the connections between the light/connector and ground need to be tight. Pull that wire off and stick test light probe in there, ground test light, then turn key to start, it should light up. Also that plug connector can become kinda lose over the years and not make a good contact to terminal stud. you can take a pair of pliers and slightly squeeze it to make it a bit out of round and it will make a better connection.

[dan84svo]

Thanks to all for the suggestions! I printed out the wiring diagram and started tracing wires. Found a problem in the solenoid push on wire circuit and in tracing wires from there, discovered that the insulation on the wiring harness to the TFI module was all crumbly and bad. If that's not the problem, it certainly needs to be fixed. Nothing looked burned up, it just pretty much disintegrated when touched.

6307

[JTurbo]

Welcome to 1984 wiring harness hell.....

[dan84svo]

Welcome to 1984 wiring harness hell.....

Thanks! I love trying to figure out wiring diagrams and gremlins! I figure since it needs rewired anyway, I am going to relocate the TFI and hopefully upgrade. Anyone else use a kit like this?

http://www.mccullyracingmotors.com/Photos/McCullyRacingMotorsTFIModuleRelocationKit02.jpg

[dagenham]

You can buy the pigtail for the ignition module. The only problem is they are not color coded wires, they are all one color.
If you feel like freezing your butt off in a junkyard you can look for a '90's Bronco and get the TFI wiring from it. The module is remote mounted from the factory on the firewall.

[dan84svo]

No, definitely not going junkyard shopping in this weather! I did a once over on the rest of the engine harness, and the TFI wiring seems to be the only bad part from what I saw. Since I'd like to get it running, I am going to put a new pigtail and TFI module on and go from there. Thanks to all for the advice and suggestions, now I have to wait for shipping...

[SnakePlisskin]

Wow, never saw a TFI connector like that! Me thinks that might be your problem or most of it. good luck on the repair!

[dan84svo]

I hope so, since splicing in a new pigtail will be easy peasy. Seems at this point that the rest of the wiring is OK, and ignition/clutch interlock/reverse switches all tested fine. Just have to wait for the package to arrive from Rock Auto and spend some quality time with a soldering iron. Ordered parts for a full tune up and a timing belt change too, so they go on next after it starts...

[MikeFleming]

Wow, never saw a TFI connector like that! Me thinks that might be your problem or most of it. good luck on the repair! ALL of the 84 harnesses that I have ever seen looked like that ten years ago - unless they were total garage queens for their entire lives. Mine died like that - and got a pigtail replacement - in the early 90's.

[dan84svo]

ALL of the 84 harnesses that I have ever seen looked like that ten years ago - unless they were total garage queens for their entire lives. Haha, mine's certainly no queen right now, but it HAS lived in the garage since 1996 and that harness probably was bad then. Anyway, still waiting for that new harness to come, so I installed the TFI module and tuneup parts since they came yesterday. Crossing my fingers now that when I swap out the bad wiring, I will have a running SVO again...

6344 out with the old, in with the new

[MikeFleming]

More accurate: Off with the old, on with the new. The old ones go into the Spares box.

[dan84svo]

More accurate: Off with the old, on with the new. The old ones go into the Spares box.

Yeah, put 'em in the glove box for emergency roadside repairs, cause if you have a spare handy the original won't go bad...

[dan84svo]

Ok, update today. got the engine compartment wiring sorted, still no crank with key. Start back probing the ign switch for the hot wire when cranked, wire is white w/ pink dots. Ran a jumper from that wire to red/blue - voila! cranks with the key. It cranks and makes an effort to fire, but unfortunately no luck in actually starting. Messed a bit with distributor hoping the timing was just a bit off, but in the end I couldn't get it running. It was nice to have it start making the right noises, but now I have to put a charger on it for a while. Y'all think there's an issue with the EEC causing the no-start? And if so, what do I need to check? I can't seem to find the answers I am looking for. In the meantime, I am going to run down the open from the white/pink wire off the ign. so I can get rid of the jumper wire.

[rodster]

You're getting there....keep it up an it will soon be :runningdog:

I'm guessing you have fresh fuel?

[dan84svo]

Snowstorms and work are hindering progress, but further diagnosis reveals no fuel pressure. I found a checklist for cranks but won't start condition (link if anyone needs it: http://www.stangnet.com/mustang-forums/resources/cranks-ok-but-no-start-checklist-for-fuel-injected-mustangs-fox-sn95-5-0l.7/ ) It's for 5.0 cars, but the info is still quite helpful. So I will go through and sort things out and hopefully post another update soon!

[k98dave]

Did you check the EEC power relay? Its usually mounted by the computer. It sends 12V to turn on both the computer and the fuel pump relay.

http://www.allfordmustangs.com/forums/attachments/5-0l-tech/87062d1262538236-eec-relay-location-ecm_eec_relay_loc.jpg

[MikeFleming]

There is a fuse link wire (brown that comes off the starter solenoid battery side that turns into a yellow colored wire as it enters the EEC harness) that sends battery positive to the power connector the EEC & FP relay, the EEC (keep-alive power). The EEC then sends power to the coil wires on those relays. It's a yellow wire at the EEC & FP relays - should be hot at all times (whenever battery is connected, ignition off or on).

[dan84svo]

I can say with a sigh of relief that today, the SVO started and ran! I went through the no start checklist, and found a fuel pressure issue (almost none) and after installing the 2 new fuel pumps, she fired up! Now I still have to sort out the glitch in the clutch safety switch (I have it rigged with a jumper), and I can take the project out of the electrical section. Not sure why my phone didn't want to cooperate with taking a video of it running, sorry about that. More updates to follow as time and weather permit.

[dan84svo]

Sorry about the video quality, it's my cheap phone and bad lighting in the garage. But hey, it's a video and should keep me from getting a one post ban, right?


http://s71.photobucket.com/user/dh3415/media/0226142132_zpsf420dcb4.mp4.html?sort=3&o=0

[MikeFleming]

Sounds like a coffee can full of rocks rolling on a hard wood floor.

Sweet! Congrats on getting her running.

[dan84svo]

Got the timing set today, the old girl is sounding pretty good despite what my phone may portray. All of my alignment marks were close from when I had the dist. pulled, it was at 9 degrees BTDC by eyeball. No stumbles, no misses and no unusual sounds. Idle settled in at around 900-1000 after it warmed up a bit, is that about right? Now I have to figure out that stupid jumper wire issue so I can put the dash back together. Too bad it's like 1 degree today and my garage is too cold to work in.

[Chalky]

as long as it doesn't sound like this you're good......

http://www.youtube.com/watch?v=cETqSbwvbCY

[MikeFleming]

Idle settled in at around 900-1000 after it warmed up a bit, is that about right? Yep. Perfect.

[rodster]

Sorry about the video quality, it's my cheap phone and bad lighting in the garage. But hey, it's a video and should keep me from getting a one post ban, right?


http://s71.photobucket.com/user/dh3415/media/0226142132_zpsf420dcb4.mp4.html?sort=3&o=0

:like3:

Great news!


http://www.youtube.com/watch?v=bPmVhyHBRAM

[BLK BRD 88]

Sounds like a coffee can full of rocks rolling on a hard wood floor.............

Do all stock SVOs sound like that, or is that an 84 specific "electro-turbine under the water fall" rumble?
Ron

[svopony]

as long as it doesn't sound like this you're good......

http://www.youtube.com/watch?v=cETqSbwvbCY

just don't let Pat near the car

[rodster]

as long as it doesn't sound like this you're good......

http://www.youtube.com/watch?v=cETqSbwvbCY

That's just mean! LOL

[dan84svo]

Whew, nothing like a little near disaster to make you feel alive! Today I am talking to a mechanic buddy at his shop, he says "bring your car down, we'll get it up on the rack and powerwash it, I have some time today so maybe we can get that wire sorted out". I rush home, get the SVO off the jackstands, and fire it up. Start backing out of the garage and down the driveway (operative word - down) and realize I have no brakes. I know, I probably could have checked the pedal before going downhill, but hey, I was pretty excited to get the car to the shop. Fortunately, I get it stopped before disaster strikes. I would bet there would have been a pretty good video of my panic if there had been a camera running. I figure at this point, today's not a good day to drive the car. So back in the garage and on the stands it sits, with a brake service next on my list of things to do.

[rodster]

Wow, that is a close one. Glad it turned out OK. Scary feeling to not had a brake pedal.

I already flushed my brake system so hopefully all is well when I get back on the road but it will be something I'm aware of.

Probably a good idea not to try putting it on a lift after that bad omen. :)