93 5.0 Starts, but not with the key
09-26-2013, 10:52 AM
#1
Junior Member
Thread Starter
93 5.0 Starts, but not with the key
Ok, here is a head scratcher. 93 F150 5.0L with 104k on the clock. I have been through the system with all of the standard checks.
New Battery with voltage at the terminals 12.8vdc
New Ignition solenoid (next to battery)
New Key cylinder (since these go out on 93s regularly)
When you turn the key to start position nothing happens
When you jump between the major terminals on ignition solenoid - starts right up
When you jump between the Hot terminal and the switch terminal on ignition solenoid - starts right up
Read voltages and everything reads as you would expect, except the wire lead to switch terminal on ignition solenoid. When you turn the key to start position, the wire lead to switch terminal on ignition solenoid only gets 4.1vdc.
Checked all the connections, fuses, and pulled the lower cover off the steering column and checked that the electrical ignition switch was firmly in place (not loose). The linkage appears to be working correctly.
So where are we getting the voltage drop?
- electrical ignition switch not making contact correctly - How to test this?
- lead to switch terminal on ignition solenoid bad - How to test this?
- Am I missing something?
New Battery with voltage at the terminals 12.8vdc
New Ignition solenoid (next to battery)
New Key cylinder (since these go out on 93s regularly)
When you turn the key to start position nothing happens
When you jump between the major terminals on ignition solenoid - starts right up
When you jump between the Hot terminal and the switch terminal on ignition solenoid - starts right up
Read voltages and everything reads as you would expect, except the wire lead to switch terminal on ignition solenoid. When you turn the key to start position, the wire lead to switch terminal on ignition solenoid only gets 4.1vdc.
Checked all the connections, fuses, and pulled the lower cover off the steering column and checked that the electrical ignition switch was firmly in place (not loose). The linkage appears to be working correctly.
So where are we getting the voltage drop?
- electrical ignition switch not making contact correctly - How to test this?
- lead to switch terminal on ignition solenoid bad - How to test this?
- Am I missing something?
Last edited by pa_trick; 09-26-2013 at 10:57 AM. Reason: typo
09-26-2013, 12:20 PM
#3
Drive like you stole it
Nevermind, I deleted ^ that post, I knew it had to be more complicated than just one wire from switch to solenoid. I tryed to upload a wire diagram but it keeps failing. From the start position power runs thru fuse 11 (20A) then to your park/neutral safety switch if you have an auto or your clutch position switch if manual. Then its on to a start relay which energizes and sends power out to your start solenoid. So try it in neutral (also wiggle shifter around while trying to start it) if you have an auto or if manual disconnect the safety switch and jump it. If that doesnt help then it may be the starter relay. Hope this makes sense. If you have the haynes manual its on page 12-54. otherwise maybe somebody else can upload it. I need to go to work.
Last edited by Rusty but trusty; 09-26-2013 at 12:39 PM.
09-26-2013, 01:41 PM
#4
Junior Member
Thread Starter
Thanks Rusty, I have been trying to find a wiring diagram for the starting system, it appears that unless you buy a manual you cannot get one..... I thought this was 2013.
The I guess the Electrical ignition switch on the steering column must have both the Start circuit and shifter safety switch for the automatic transmission. however, I need a diagram to figure out the pin-outs. The search continues.
The I guess the Electrical ignition switch on the steering column must have both the Start circuit and shifter safety switch for the automatic transmission. however, I need a diagram to figure out the pin-outs. The search continues.
09-26-2013, 02:10 PM
#5
Drive like you stole it
No, the park/neutral safety switch should be separate from the ignition tumbler, I would think it would be located on the shifter on the steering column. Have you tried starting it in neutral?
09-26-2013, 02:27 PM
#7
Junior Member
Thread Starter
Found it, my local library has a great on-line reference section.
The circuit leaves the Electric Ignition Switch as Red/Lt Blue then goes to the Clutch Interlock Switch. For Automatic Trans this switch is jumpered and the wire goes to White and Pink going into the Backup/Neutral Safety Switch and comes out of that as Red/Lt Blue again. There are a couple connectors, but that is the lead that goes to the activation terminal on the Starter Relay (solenoid next to the battery).
Now to find the Backup/Neutral Safety Switch
The circuit leaves the Electric Ignition Switch as Red/Lt Blue then goes to the Clutch Interlock Switch. For Automatic Trans this switch is jumpered and the wire goes to White and Pink going into the Backup/Neutral Safety Switch and comes out of that as Red/Lt Blue again. There are a couple connectors, but that is the lead that goes to the activation terminal on the Starter Relay (solenoid next to the battery).
Now to find the Backup/Neutral Safety Switch
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09-26-2013, 03:02 PM
#8
Junior Member
Thread Starter
Found it. This has been a real research project. The Backup/Neutral Safety Switch on 89 - 96 f150s is located on the side of the transmission where the shifter linkage attaches.
Time to crawl under the truck I will update this when I find the solution.
THANKS for the help Rusty.
Time to crawl under the truck I will update this when I find the solution.
THANKS for the help Rusty.
09-26-2013, 06:25 PM
#9
Drive like you stole it
Found it, my local library has a great on-line reference section.
The circuit leaves the Electric Ignition Switch as Red/Lt Blue then goes to the Clutch Interlock Switch. For Automatic Trans this switch is jumpered and the wire goes to White and Pink going into the Backup/Neutral Safety Switch and comes out of that as Red/Lt Blue again. There are a couple connectors, but that is the lead that goes to the activation terminal on the Starter Relay (solenoid next to the battery).
Now to find the Backup/Neutral Safety Switch
The circuit leaves the Electric Ignition Switch as Red/Lt Blue then goes to the Clutch Interlock Switch. For Automatic Trans this switch is jumpered and the wire goes to White and Pink going into the Backup/Neutral Safety Switch and comes out of that as Red/Lt Blue again. There are a couple connectors, but that is the lead that goes to the activation terminal on the Starter Relay (solenoid next to the battery).
Now to find the Backup/Neutral Safety Switch
The starter relay is not the solenoid next to the battery, the relay controls the solenoid. Two seperate parts.
09-26-2013, 06:59 PM
#10
Junior Member
Thread Starter
Ok so I pulled the Backup/Neutral Safety Switch off the transmission and discovered that it was a lot more complex that one would think. Ok so more research and I fell across the following to posts on another forum (ford-trucks)
Here is Why:
That low voltage I was getting on the Control terminal is actually sensor voltage. Ah-hah!
So, my occasional (VERY occasional) code for a neutral safety switch? I thought, "so what, I sometimes have to push up into park to get it started, not vital, it can wait". You know, the neutral safety switch on my C6 in my F150 and other Bronco doesn't do a whole lot, so why bother.
Well, my tranny has been acting weird, did some searches on the subject and everything led to the MLPS, Transmission Range sensor or what Autozone and my codes call it, a neutral safety switch. Saw CM throw the code again, so I went ahead and changed it.
I now have a whole new Bronco. Everything from my idle in park, to shifting to engine power to.. well, just about everything in the Bronco is working better.
I thought I had replaced or fixed everything in the finicky speed density sensor chain and was just fighting a tired, worn engine, no power, rough idles, you know the deal.. not thinking a neutral safety switch was part of this chain and thinking it was something totally different than the MLPS I kept hearing about. Sure enough, signal return to TPS among other things.
So, if anyone hasn't done it yet with a 94' or earlier, DO IT NOW. Trust me! it helps in areas you don't expect and doesn't seem to throw codes very often, if at all. No joke when I say I feel like I just gained 100 horsepower and upped my mileage at the same time.
and I had no clue this Bronco could idle at 550RPMs and sound so smooth..
edit: Oh yeah, one more thing.. my loud CLUNK is gone when shifting from park to reverse and vice versa. Apparently my engine was reving high in between shifts and causing it, the MLPS change stopped it completely.
Well, my tranny has been acting weird, did some searches on the subject and everything led to the MLPS, Transmission Range sensor or what Autozone and my codes call it, a neutral safety switch. Saw CM throw the code again, so I went ahead and changed it.
I now have a whole new Bronco. Everything from my idle in park, to shifting to engine power to.. well, just about everything in the Bronco is working better.
I thought I had replaced or fixed everything in the finicky speed density sensor chain and was just fighting a tired, worn engine, no power, rough idles, you know the deal.. not thinking a neutral safety switch was part of this chain and thinking it was something totally different than the MLPS I kept hearing about. Sure enough, signal return to TPS among other things.
So, if anyone hasn't done it yet with a 94' or earlier, DO IT NOW. Trust me! it helps in areas you don't expect and doesn't seem to throw codes very often, if at all. No joke when I say I feel like I just gained 100 horsepower and upped my mileage at the same time.
and I had no clue this Bronco could idle at 550RPMs and sound so smooth..
edit: Oh yeah, one more thing.. my loud CLUNK is gone when shifting from park to reverse and vice versa. Apparently my engine was reving high in between shifts and causing it, the MLPS change stopped it completely.
The REASON for this is simple. All resistive electrical components (which is to say MOST of the sensors in our vehicles) change resistance value as they are exposed to temperature and humidity extremes. Eventually, that resistance value changes enough to affect the voltages that the computer is programmed to "look for". When that happens, the computer compensates whether its really necessary or not. The result is a loss of performance. This isn't to say you should change all the sensors with each tune up! It just means that if the vehicle you are driving is more than 10 years old and still has most of the original sensors, you should consider replacement sooner rather than later and don't hesitate if you are seeing recurring fault codes as this is indicative of a sensor that has reached a "marginal" functionality and is probably doing more harm than good for your performance and mileage.
MLPS - uses resistors of different values to alter the voltage that the computer sees from it. The various voltages that come back to the computer "tell" it what gear has been selected. Each gear has a given resistor that sends a specific voltage back to the computer.
EVP - is a varistor. (Variable Resistor) that changes voltage as the EGR valve opens and closes. Again the change "tells" the computer the position of the EGR valve.
TPS - is a potentiometer (another type of variable resistance device). Varying voltage from it "tell"s the computer how far open the throttle plates are.
ECT and ACT are Thermistors (Thermal reactive resistors). These two change resistance value as they warm up and cool down. They "tell" the computer engine coolant temperature and temperature of the air coming into the intake.
The one thing to ALWAYS remember as well is the fact that ALL but TWO of the sensors in our trucks MUST be fed VREF (the +5VDC power from the computer). If this reference voltage is interrupted, the computer will see it as a problem with that sensor. If this voltage is lower than about +4.75 VDC as it comes TO each sensor, this throws all of the readings coming FROM each sensor off.
MLPS - uses resistors of different values to alter the voltage that the computer sees from it. The various voltages that come back to the computer "tell" it what gear has been selected. Each gear has a given resistor that sends a specific voltage back to the computer.
EVP - is a varistor. (Variable Resistor) that changes voltage as the EGR valve opens and closes. Again the change "tells" the computer the position of the EGR valve.
TPS - is a potentiometer (another type of variable resistance device). Varying voltage from it "tell"s the computer how far open the throttle plates are.
ECT and ACT are Thermistors (Thermal reactive resistors). These two change resistance value as they warm up and cool down. They "tell" the computer engine coolant temperature and temperature of the air coming into the intake.
The one thing to ALWAYS remember as well is the fact that ALL but TWO of the sensors in our trucks MUST be fed VREF (the +5VDC power from the computer). If this reference voltage is interrupted, the computer will see it as a problem with that sensor. If this voltage is lower than about +4.75 VDC as it comes TO each sensor, this throws all of the readings coming FROM each sensor off.