Basic Electrical Troubleshooting for the RX-7
06-26-04, 12:40 AM
#1
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Thread Starter
Basic Electrical Troubleshooting for the RX-7
All right guys, it seems every day I'm on the forum someone needs electrical help, but doesn't quite know how to use a meter, so in the attempt to alleviate my carpal-tunnel symptoms from popping up due to all the typing I'm doing, here is a basic "electrical troubleshooting 101"...
Basic troubleshooting tools
At the very least, you will need a multi-meter capable of reading voltage up to 15 volts, and resistance from 0 to infinity (or "open). I've been using high-dollar Fluke meters at work for years, but use a couple of cheap "Radio Shack" type analog meters at home, that's really all you need to cover the spectrum of troubleshooting you will be doing on your RX-7. A set of jumper wires with "alligator clip" ends also come in very handy, and allow you to free your hands up for other tasks. Small pieces of solid wire, such as small paper clips or aircraft safety wire, also can be used for making jumpers.
Basic Circuits
A complete circuit consist of the power side, the component(s) using the power, and the ground. Circuits can, of course, be very complex, consisting of several switches, coils, resistors, etc, but for a circuit to function it must have all of the basic 3 attributes mentioned above. If any one of the 3 should fail, the circuit will not function as intended. Luckily 95% of our cars' circuits are known as "simple circuits", and are very easy to troubleshoot with a simple $10 meter.
Reading Circuits
There are only 2 "versions" of the magic we call electricity we need to concern ourselves with while troubleshooting our cars; voltage, and resistance. Voltage is read 99% of the time with the black (negative) meter lead placed on the car's ground, in this case consisting of the entire metal frame of the car, and every metal part, including bolts, studs, and the engine, that are bonded to the chassis either by direct contact, or by seperate wiring (known as "bonding"). Note that almost any bare metal surface is considered a ground. The negative terminal of your battery is also considered a ground. The red (positive) meter lead will be placed on the circuit wire or component connector to read the actual voltage, which is nothing more than the "difference in electrical potential" compared to the ground. The easiest way to comprehend this is to consider the ground voltage, or "potential", to always be zero, thus any voltage read on the meter should always be "positive" voltage. Voltage is always read with the circuit in question energized, or powered, either by the battery itself (called a "hot bus circuit", because the key need not be on), or by a circuit powered through the activation of the ignition switch. If the needle on the meter jumps backwards off the scale when taking voltage readings, your meter leads are reversed, or you are not checking the circuit properly. Note that the majority of voltage readings are taken BEFORE the components of the circuit, for instance, if we wanted to check to make sure the boost/pressure sensor is getting power, we would check the wiring terminal at the plug before it goes into the sensor (using the red lead, with black lead on a ground). If we checked the wire that comes FROM the sensor and goes to a ground, the voltage should always be zero; if it's not, the ground is bad. So basically, voltage readings check that we are getting power to a component. Check to make sure the meter is set to a scale range corrresponding to the voltage you're expecting to see (since the vast majority of our readings will be 14 volts and less, a 15 or 25 volt scale works nicely).
Resistance readings on a meter are used to check the internal integrity of a component (such as the CAS coils), or the wiring from one point to another in the circuit. Note that ALL power should be removed from the car before taking resistance readings. If you're just starting out using a meter for troubleshooting circuits, remove the negative terminal from the battery to accomplish this. Once you become familiar with which circuits have power at all times, which have power with the key on, etc...you may leave the negative terminal on if you are fairly certain the circuit in question will not be powered for your readings. Another point to remember is that your metal chassis is actually one big wire- if you need to read a stretch of wiring that is obviously longer than the meter leads can stretch, ground the beginning of the circuit using the alligator clips, and read the other end of the circuit to ground with the meter. If you get something close to zero ohms, the wiring is good. Note also that your meter has its own internal "power supply", usually a 1.5 or 9 volt battery. This battery is used to send a "calibrated" current through the wiring or component you're checking. The meter "knows" how much resistance is in the circuit by comparing the current coming back to the current it sent out. Hence the need to make sure the circuit you're testing is not already powered. There is also an internal fuse in almost every meter to protect the resistance reading circuitry, and, when we goof up and leave power on a circuit for a resistance reading, the fuse will blow. So, if you're meter does not seem to work on the resistance settings, check that fuse. Resistance readings are usually not polarity sensitive, which means it doesn't matter which meter probe goes where, as long as they are set up correctly to read only what you want them too. You usually must isolate a component or circuit to get a correct resistance reading, otherwise, if everything is still connected, you can (and will) read the entire circuit, through the fuses, grounds, and even the battery! Most analog meters must also be "zeroed" before a correct reading can be taken- this is accomplished by touching the two probe ends together, and adjusting a **** or dial until the meter's scale reads exactly 0.
Types of faults
Opens are a fault in the circuit caused by a wire, coil, ground terminal, etc that has seperated, breaking the normal electrical flow of the circuit. Open circuits are the easiest to track down using your meter. For instance, if you don't have that 12 volts at the boost sensor we talked about earlier, you know that the power side of the circuit has an open. If the 12 volts is there, the open is either in the boost sensor itself, or the ground circuit. Note that a fuse blowing, due to a short, will cause an open circuit. Fuses should always be the first items to check when something's not working. An open can also be troubleshot using resistance readings.
A short in a circuit is every electrician's nightmare. The most effective way to find a short doesn't require the use of a meter at all, but you must be fairly proficient at reading wiring schematics (more on this later). The idea is to "cut" the circuit in half by pulling a component or connector at the approximately half way point of the circuit. Then, insert another fuse. If this fuse blows, you know the problem is in the first half of the circuit, you've just ruled out 50% of the circuit with one simple step. Accordingly, if the fuse doesn't blow, you know that the first half is good, and the problem lies in the second half. Continue splitting the "problem halves" in half again, until you've got the culprit. We have so many coils in so many circuits on our cars (solenoids, relays, motors, etc), that it's nearly impossible to read a circuit for a short on our cars with a meter (the total resistance of an entire circuit with a couple of solenoids will be close to zero ohms, which would seem a short, even though the circuit is perfectly fine). Circuits with many bulbs also display this characteristic. I also must take the opportunity here to warn against putting a higher amperage rated fuse into a circuit just because the original rating keeps blowing. If a fuse blows, you've got a problem, and trying to cover the problem with a larger fuse can lead to melted wiring insulation and possibly fire. We have enough fires on our cars as it is, please don't make yours an electrical one...
When our cars are doing something that really baffles us, the most effective troubleshooting can be done at the ECU itself. Section 4 of the FSM ('86 to '88 cars) lists all the relevant information on pin locations, sensor inputs, normal voltage readings, etc..., so it's imperative you get to know this info.
Unless you're rich, it doesn't make sense to buy parts to throw at a problem on your car without first troubleshooting to verify that the part is even getting voltage, or has a good ground. So start learning how to use that meter now, it will save you a lot of heartache and money down the road. Even if the car's running great, now's the perfect opportunity to get to know those ECU input voltages! And remember, the majority of the times our cars break on us, it's because of something WE did to the car, so keep that in mind as your first step to successful troubleshooting.
Now, on to these confusing FSM wiring schematics: for some strange reason Mazda decided not to show us an entire circuit on one page that clearly displays the fuse name/ rating, and the "proper" ground type symbols. With a little time spent with the schematics, however, it can all become clear. Using the first couple of pages of the wiring manual (which denotes main power circuitry and fuse ratings), it is easy enough to track down those fuse "numbers" at the tops of the rest of the schematics. After you've figured out which circuit has power when (Battery, Accessory, Ign 1, Ign2, and Start) from the horizontal lines at the tops of the schematics, you can figure out what fuse it must be, from those first two pages (it sounds confusing, I know, but you'll see it more clearly with the schematics in front of ya). You will also realize that our cabin fuse boxes are "tiered", with the Batt powered fuses on the top row, the Access powered fuses on the next row down, and so forth. Same thing with the grounds, but you'll use on of the last pages in the wiring manual, it will show you ground locations and corresponding numbers, that will match the numbers shown at the bottoms of the regular schematics.
Good luck, don't zap yourself, and don't blow that meter fuse!
Wayne
Basic troubleshooting tools
At the very least, you will need a multi-meter capable of reading voltage up to 15 volts, and resistance from 0 to infinity (or "open). I've been using high-dollar Fluke meters at work for years, but use a couple of cheap "Radio Shack" type analog meters at home, that's really all you need to cover the spectrum of troubleshooting you will be doing on your RX-7. A set of jumper wires with "alligator clip" ends also come in very handy, and allow you to free your hands up for other tasks. Small pieces of solid wire, such as small paper clips or aircraft safety wire, also can be used for making jumpers.
Basic Circuits
A complete circuit consist of the power side, the component(s) using the power, and the ground. Circuits can, of course, be very complex, consisting of several switches, coils, resistors, etc, but for a circuit to function it must have all of the basic 3 attributes mentioned above. If any one of the 3 should fail, the circuit will not function as intended. Luckily 95% of our cars' circuits are known as "simple circuits", and are very easy to troubleshoot with a simple $10 meter.
Reading Circuits
There are only 2 "versions" of the magic we call electricity we need to concern ourselves with while troubleshooting our cars; voltage, and resistance. Voltage is read 99% of the time with the black (negative) meter lead placed on the car's ground, in this case consisting of the entire metal frame of the car, and every metal part, including bolts, studs, and the engine, that are bonded to the chassis either by direct contact, or by seperate wiring (known as "bonding"). Note that almost any bare metal surface is considered a ground. The negative terminal of your battery is also considered a ground. The red (positive) meter lead will be placed on the circuit wire or component connector to read the actual voltage, which is nothing more than the "difference in electrical potential" compared to the ground. The easiest way to comprehend this is to consider the ground voltage, or "potential", to always be zero, thus any voltage read on the meter should always be "positive" voltage. Voltage is always read with the circuit in question energized, or powered, either by the battery itself (called a "hot bus circuit", because the key need not be on), or by a circuit powered through the activation of the ignition switch. If the needle on the meter jumps backwards off the scale when taking voltage readings, your meter leads are reversed, or you are not checking the circuit properly. Note that the majority of voltage readings are taken BEFORE the components of the circuit, for instance, if we wanted to check to make sure the boost/pressure sensor is getting power, we would check the wiring terminal at the plug before it goes into the sensor (using the red lead, with black lead on a ground). If we checked the wire that comes FROM the sensor and goes to a ground, the voltage should always be zero; if it's not, the ground is bad. So basically, voltage readings check that we are getting power to a component. Check to make sure the meter is set to a scale range corrresponding to the voltage you're expecting to see (since the vast majority of our readings will be 14 volts and less, a 15 or 25 volt scale works nicely).
Resistance readings on a meter are used to check the internal integrity of a component (such as the CAS coils), or the wiring from one point to another in the circuit. Note that ALL power should be removed from the car before taking resistance readings. If you're just starting out using a meter for troubleshooting circuits, remove the negative terminal from the battery to accomplish this. Once you become familiar with which circuits have power at all times, which have power with the key on, etc...you may leave the negative terminal on if you are fairly certain the circuit in question will not be powered for your readings. Another point to remember is that your metal chassis is actually one big wire- if you need to read a stretch of wiring that is obviously longer than the meter leads can stretch, ground the beginning of the circuit using the alligator clips, and read the other end of the circuit to ground with the meter. If you get something close to zero ohms, the wiring is good. Note also that your meter has its own internal "power supply", usually a 1.5 or 9 volt battery. This battery is used to send a "calibrated" current through the wiring or component you're checking. The meter "knows" how much resistance is in the circuit by comparing the current coming back to the current it sent out. Hence the need to make sure the circuit you're testing is not already powered. There is also an internal fuse in almost every meter to protect the resistance reading circuitry, and, when we goof up and leave power on a circuit for a resistance reading, the fuse will blow. So, if you're meter does not seem to work on the resistance settings, check that fuse. Resistance readings are usually not polarity sensitive, which means it doesn't matter which meter probe goes where, as long as they are set up correctly to read only what you want them too. You usually must isolate a component or circuit to get a correct resistance reading, otherwise, if everything is still connected, you can (and will) read the entire circuit, through the fuses, grounds, and even the battery! Most analog meters must also be "zeroed" before a correct reading can be taken- this is accomplished by touching the two probe ends together, and adjusting a **** or dial until the meter's scale reads exactly 0.
Types of faults
Opens are a fault in the circuit caused by a wire, coil, ground terminal, etc that has seperated, breaking the normal electrical flow of the circuit. Open circuits are the easiest to track down using your meter. For instance, if you don't have that 12 volts at the boost sensor we talked about earlier, you know that the power side of the circuit has an open. If the 12 volts is there, the open is either in the boost sensor itself, or the ground circuit. Note that a fuse blowing, due to a short, will cause an open circuit. Fuses should always be the first items to check when something's not working. An open can also be troubleshot using resistance readings.
A short in a circuit is every electrician's nightmare. The most effective way to find a short doesn't require the use of a meter at all, but you must be fairly proficient at reading wiring schematics (more on this later). The idea is to "cut" the circuit in half by pulling a component or connector at the approximately half way point of the circuit. Then, insert another fuse. If this fuse blows, you know the problem is in the first half of the circuit, you've just ruled out 50% of the circuit with one simple step. Accordingly, if the fuse doesn't blow, you know that the first half is good, and the problem lies in the second half. Continue splitting the "problem halves" in half again, until you've got the culprit. We have so many coils in so many circuits on our cars (solenoids, relays, motors, etc), that it's nearly impossible to read a circuit for a short on our cars with a meter (the total resistance of an entire circuit with a couple of solenoids will be close to zero ohms, which would seem a short, even though the circuit is perfectly fine). Circuits with many bulbs also display this characteristic. I also must take the opportunity here to warn against putting a higher amperage rated fuse into a circuit just because the original rating keeps blowing. If a fuse blows, you've got a problem, and trying to cover the problem with a larger fuse can lead to melted wiring insulation and possibly fire. We have enough fires on our cars as it is, please don't make yours an electrical one...
When our cars are doing something that really baffles us, the most effective troubleshooting can be done at the ECU itself. Section 4 of the FSM ('86 to '88 cars) lists all the relevant information on pin locations, sensor inputs, normal voltage readings, etc..., so it's imperative you get to know this info.
Unless you're rich, it doesn't make sense to buy parts to throw at a problem on your car without first troubleshooting to verify that the part is even getting voltage, or has a good ground. So start learning how to use that meter now, it will save you a lot of heartache and money down the road. Even if the car's running great, now's the perfect opportunity to get to know those ECU input voltages! And remember, the majority of the times our cars break on us, it's because of something WE did to the car, so keep that in mind as your first step to successful troubleshooting.
Now, on to these confusing FSM wiring schematics: for some strange reason Mazda decided not to show us an entire circuit on one page that clearly displays the fuse name/ rating, and the "proper" ground type symbols. With a little time spent with the schematics, however, it can all become clear. Using the first couple of pages of the wiring manual (which denotes main power circuitry and fuse ratings), it is easy enough to track down those fuse "numbers" at the tops of the rest of the schematics. After you've figured out which circuit has power when (Battery, Accessory, Ign 1, Ign2, and Start) from the horizontal lines at the tops of the schematics, you can figure out what fuse it must be, from those first two pages (it sounds confusing, I know, but you'll see it more clearly with the schematics in front of ya). You will also realize that our cabin fuse boxes are "tiered", with the Batt powered fuses on the top row, the Access powered fuses on the next row down, and so forth. Same thing with the grounds, but you'll use on of the last pages in the wiring manual, it will show you ground locations and corresponding numbers, that will match the numbers shown at the bottoms of the regular schematics.
Good luck, don't zap yourself, and don't blow that meter fuse!
Wayne
06-30-04, 11:41 AM
#2
Lives on the Forum
Thread Starter
OK, on to grounds...
I've noticed a lot of confusion on the topic of adding ground wires to our cars. The ground wire is, simply, the other side of the circuit (component) than the positive, or power, wire is. Nothing more, nothing less. Making it bigger will NOT help the circuit "flow" better, it's like adding a 1" plumbing pipe to a 3/4" water supply circuit- what does that accomplish?
Some real numbers to wrap your head around: A 12 gage wire is perfectly capable of handling 2400 watts of power, without overheating the insulation. Using a derivative of ohm's law, on a 12 volt system this means the wire is capable of supporting a 200 amp load! Anything on our cars suck down 200 amps besides the starter? Maybe some of your sound sytems!
Using the same analogy, a 14 gage wire will support 1800 watts, or 150A. Know of any items on the car that draw 150A? The biggest fuse we have (on our S4's) is an 80A, and if designed correctly (I've seen nothing so far to suggest it hasn't), the fuse will blow long before the wiring ever gets hot enough to do any damage (I know, I know, some of you have "smoke checked" the wiring due to a catastophic short, it happens).
So, using the above, we can deduce that 14 gage wiring is more than sufficient to handle the electrical loads of our cars, including the grounds, except the starter and charging circuits, of course.
In all the years I have been troubleshooting electrical systems on aircraft, I have never, ever traced a fault to a bad ground. The main reason for this is evidently that aircraft manufacturers figured out how to properly ground a terminal many years ago, and Mazda didn't...The proper way to ground a ring terminal (which is the best way to ground a wire due to the large surface area of the contact with the chassis) is to "make" a small circular area of clean bare metal, a little larger than the terminal, then bolt the terminal directly on top of the chassis metal. Special anti-corrosion compunds are then applied over the assembly to keep any corrosion from forming on the metal surfaces (I just use a dab of RTV to accomplish this). Mazda decided to put the terminal over a painted surface, and let the hardware (threads of the bolt against the nutplate threads) do the job of grounding. This worked well when the cars were new, but these points have become dirty and corroded over the years.
If you think you might be having grounding issues, find all of your OEM grounding points (look at the last page of the FSM wiring manual for locations). Begin in the engine bay and "clean" them up per instructions above. The most important ground (as far as the ECU is concerned) is the two-wire "gang" ground, located at the top left side of the rear rotor housing. You must pull the upper intake manifold off for easy access, unless you're Gumby.
On to the controversial "boost sensor grounding". As I've stated in several posts before, grounding this sensor's alleged "ground" wire is WRONG. The boost sensor does not have a ground wire that actually bonds to the chassis- the wire in question leads to the ECU, who decides when to ground the sensor. Several other sensors also are wired like this, and the injectors are also "grounded" through the ECU. You wouldn't ground your injectors' wiring, would you? Of course not, then they would be open and flowing 100% of the time, with absolutely no ECU control over them. Same scenario with the sensors, guys, don't take away ECU control from them, it'll just lead to problems...
You guys adding all these beefy "00" gage cables all over the engine compartment are at least accomplishing one thing- it's refered to as "bonding", and it's used to ensure that the negative ground "potential" is the same throughout the chassis. Great job...Problem is, you only need small gage wiring to accomplish bonding. If the OEM grounds are good (and they will be after you fix them), the bonding jumpers are there to handle "stray" current, not circuit current...
And I'll say it again, one last time- If you "fixed" something by adding a ground wire, then your original ground(s) was in need of repair, and it probably supports more components than just the one you were trying to fix, so fix that old ground! And any cracking, heat stressed wiring you may find while searching for your grounds. A spool of 14 gage stranded copper wire, a good pair of crimpers, and a box of assorted butt splices and ring terminals should cost you far less than $20...Money well spent, and after it's fixed the right way, you won't have to worry about it for years to come...
Again, good luck with all you do, ... Wayne...
I've noticed a lot of confusion on the topic of adding ground wires to our cars. The ground wire is, simply, the other side of the circuit (component) than the positive, or power, wire is. Nothing more, nothing less. Making it bigger will NOT help the circuit "flow" better, it's like adding a 1" plumbing pipe to a 3/4" water supply circuit- what does that accomplish?
Some real numbers to wrap your head around: A 12 gage wire is perfectly capable of handling 2400 watts of power, without overheating the insulation. Using a derivative of ohm's law, on a 12 volt system this means the wire is capable of supporting a 200 amp load! Anything on our cars suck down 200 amps besides the starter? Maybe some of your sound sytems!
Using the same analogy, a 14 gage wire will support 1800 watts, or 150A. Know of any items on the car that draw 150A? The biggest fuse we have (on our S4's) is an 80A, and if designed correctly (I've seen nothing so far to suggest it hasn't), the fuse will blow long before the wiring ever gets hot enough to do any damage (I know, I know, some of you have "smoke checked" the wiring due to a catastophic short, it happens).
So, using the above, we can deduce that 14 gage wiring is more than sufficient to handle the electrical loads of our cars, including the grounds, except the starter and charging circuits, of course.
In all the years I have been troubleshooting electrical systems on aircraft, I have never, ever traced a fault to a bad ground. The main reason for this is evidently that aircraft manufacturers figured out how to properly ground a terminal many years ago, and Mazda didn't...The proper way to ground a ring terminal (which is the best way to ground a wire due to the large surface area of the contact with the chassis) is to "make" a small circular area of clean bare metal, a little larger than the terminal, then bolt the terminal directly on top of the chassis metal. Special anti-corrosion compunds are then applied over the assembly to keep any corrosion from forming on the metal surfaces (I just use a dab of RTV to accomplish this). Mazda decided to put the terminal over a painted surface, and let the hardware (threads of the bolt against the nutplate threads) do the job of grounding. This worked well when the cars were new, but these points have become dirty and corroded over the years.
If you think you might be having grounding issues, find all of your OEM grounding points (look at the last page of the FSM wiring manual for locations). Begin in the engine bay and "clean" them up per instructions above. The most important ground (as far as the ECU is concerned) is the two-wire "gang" ground, located at the top left side of the rear rotor housing. You must pull the upper intake manifold off for easy access, unless you're Gumby.
On to the controversial "boost sensor grounding". As I've stated in several posts before, grounding this sensor's alleged "ground" wire is WRONG. The boost sensor does not have a ground wire that actually bonds to the chassis- the wire in question leads to the ECU, who decides when to ground the sensor. Several other sensors also are wired like this, and the injectors are also "grounded" through the ECU. You wouldn't ground your injectors' wiring, would you? Of course not, then they would be open and flowing 100% of the time, with absolutely no ECU control over them. Same scenario with the sensors, guys, don't take away ECU control from them, it'll just lead to problems...
You guys adding all these beefy "00" gage cables all over the engine compartment are at least accomplishing one thing- it's refered to as "bonding", and it's used to ensure that the negative ground "potential" is the same throughout the chassis. Great job...Problem is, you only need small gage wiring to accomplish bonding. If the OEM grounds are good (and they will be after you fix them), the bonding jumpers are there to handle "stray" current, not circuit current...
And I'll say it again, one last time- If you "fixed" something by adding a ground wire, then your original ground(s) was in need of repair, and it probably supports more components than just the one you were trying to fix, so fix that old ground! And any cracking, heat stressed wiring you may find while searching for your grounds. A spool of 14 gage stranded copper wire, a good pair of crimpers, and a box of assorted butt splices and ring terminals should cost you far less than $20...Money well spent, and after it's fixed the right way, you won't have to worry about it for years to come...
Again, good luck with all you do, ... Wayne...
06-30-04, 12:06 PM
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Originally posted by WAYNE88N/A
On to the controversial "boost sensor grounding". As I've stated in several posts before, grounding this sensor's alleged "ground" wire is WRONG. The boost sensor does not have a ground wire that actually bonds to the chassis- the wire in question leads to the ECU, who decides when to ground the sensor. Several other sensors also are wired like this, and the injectors are also "grounded" through the ECU. You wouldn't ground your injectors' wiring, would you? Of course not, then they would be open and flowing 100% of the time, with absolutely no ECU control over them. Same scenario with the sensors, guys, don't take away ECU control from them, it'll just lead to problems...
On to the controversial "boost sensor grounding". As I've stated in several posts before, grounding this sensor's alleged "ground" wire is WRONG. The boost sensor does not have a ground wire that actually bonds to the chassis- the wire in question leads to the ECU, who decides when to ground the sensor. Several other sensors also are wired like this, and the injectors are also "grounded" through the ECU. You wouldn't ground your injectors' wiring, would you? Of course not, then they would be open and flowing 100% of the time, with absolutely no ECU control over them. Same scenario with the sensors, guys, don't take away ECU control from them, it'll just lead to problems...
Other than that, it's a great write-up, I'm the one who voted it to get archived.
06-30-04, 01:32 PM
#4
RX-7 Bad Ass
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The boost sensor ground is also in a TSB issued by Mazda back in the '80s. I've never really seen grounding the boost sensor to solve anything, though. The TSB only applies to the early '86-88 cars, BTW.
But, nice writeup!
Dale
But, nice writeup!
Dale
06-30-04, 02:32 PM
#5
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Thread Starter
You are correct, SonicRat, the injectors were the closest analogy to the sensor circuit that popped in my head- no confusion intended.
Grounding the injector (With it's normal ground circuit wire- the one that runs to the ECU) wouldn't burn the fuse. As long as the injector coil is good, adding a ground there would just "click" it on, like any other relay coil would do. Granted, if it was powered continuously, it would burn out sooner or later.
I have answered several PM's from guys that have grounded that boost sensor only to find their performance suffering worse. After removing this ground, everything magically "fixed" itself again. Anybody who's worked with wiring schematics could take a 10 second look at that ECU & sensor diagram and notice that there are no grounds to any of the sensors, and yes, the ECU provides it, and I'm with you, I doubt it does any "switching" at all with these sensors. However, they share a common ground for a reason, and adding an additional ground to the one sensor could feasibly (and obviously does) screw with the ECU's head.
Constructive criticism is always welcome. I'll be the first to admit I've still got a lot to learn about our cars, but the main reason I started this thread was for educational purposes for the guys who all of a sudden find themselves with a 17 year-old car, and not a clue as to how to troubleshoot it...
Thanks for the input guys
Grounding the injector (With it's normal ground circuit wire- the one that runs to the ECU) wouldn't burn the fuse. As long as the injector coil is good, adding a ground there would just "click" it on, like any other relay coil would do. Granted, if it was powered continuously, it would burn out sooner or later.
I have answered several PM's from guys that have grounded that boost sensor only to find their performance suffering worse. After removing this ground, everything magically "fixed" itself again. Anybody who's worked with wiring schematics could take a 10 second look at that ECU & sensor diagram and notice that there are no grounds to any of the sensors, and yes, the ECU provides it, and I'm with you, I doubt it does any "switching" at all with these sensors. However, they share a common ground for a reason, and adding an additional ground to the one sensor could feasibly (and obviously does) screw with the ECU's head.
Constructive criticism is always welcome. I'll be the first to admit I've still got a lot to learn about our cars, but the main reason I started this thread was for educational purposes for the guys who all of a sudden find themselves with a 17 year-old car, and not a clue as to how to troubleshoot it...
Thanks for the input guys
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06-30-04, 03:20 PM
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It appears to be Isengard tower. Anywho, I've noticed great improvements by adding the pressure sensor ground, even after cleaning all my stock points, not sure if it's faulty wiring (highly possible, my harness is a bit crusty). Anywho, if you ground the pulse on the injector by tapping the wire and grounding it, you will fry the EGI fuse (because the ECU feeds it +12v when it's not being pulsed) I've had that happen a lot if people solder on different connectors and use electrical tape instead of heat shrink and it comes off 
06-30-04, 03:39 PM
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well im a 17 year old guy who just found himself with a 17 year old car, and i sure dont have any idea where to start when it comes to electrical systems. this thread is a great start on my road to understanding ohms and amps and volts. thanks for the effort bro! but is there a weblink or book you can reccommend that gives a basic backround on circuits, resistors, solenoids and the like? i want to learn but im not sure where to start.. unless i take electronics next year...
06-30-04, 03:55 PM
#11
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Basic Car Electronics (Yes it is directed more towards the car audio side of things, but it does give you a good idea at least..)
Great site, before I started my engineering degree it helped me a shitload to understand how to work around my cars electrical system.
Great site, before I started my engineering degree it helped me a shitload to understand how to work around my cars electrical system.
Last edited by White_FC; 06-30-04 at 03:58 PM.
06-30-04, 04:43 PM
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SonicRat, you must be grounding the wrong injector wire, man...You WILL blow the fuse if you ground the wire that goes from the main relay to the injector, but you shouldn't blow it if you ground the one that runs from the injector to the ECU. If it does blow then, your injector coil is shorted (it happens). I can sit here all day with my "homemade" injector cleaner/tester and "click" the sucker until I pass out, with direct feeds from the car battery, without shorting anything. The injector coil is the "component" that uses the power, any wire grounded after the "component" will not blow a fuse, unless the component is internally shorted.
Mycarisolderthanme, (great name, man)- Go to your local bookstore, or search on the net for some good tutorials. College courses would be even better- a good teacher is able to use analogies (like the water plumbing pipe diameters I used above) that help you understand the nature of the beast...
Mycarisolderthanme, (great name, man)- Go to your local bookstore, or search on the net for some good tutorials. College courses would be even better- a good teacher is able to use analogies (like the water plumbing pipe diameters I used above) that help you understand the nature of the beast...
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msilvia
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09-11-15 12:13 PM
