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Thread: Diagnosing the Symptoms of a Bad Engine Ground

  1. #1
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    Diagnosing the Symptoms of a Bad Engine Ground

    On our old cars we have to carefully check the ground wires. Yesterday we replaced on a Mitsubishi Town Ace Minicar the timing belt and the belts for alternator + defective belt tensioner (bearing was running rough), water pump and AC compressor and the water pump. After installing the timing belt we wanted to check the correct installation of the timing belt before we assembled further, so we wanted to briefly run the engine via the starter, all other belts not installed, also the CPS was not installed. So I turned the ignition key, but almost nothing happened, just a few cranks and it sounded like the battery is empty, next try only the starter solenoid was clicking and nothing more. Tested the battery, completely fully charged, so we checked more.
    And we found the cause, when removing the cover of the timing belt, we also had to disconnect a relatively thin wire from that, and that was the ground cable for the engine! Connected that, immy the starter worked normal. So we could assemble the rest and car runs well again without any noise.

    Back to E32, there ground cables are also very important and some of you have seen rotten cables and oxized connections which you should better replace asap. Here a good write-up by Dan Ferrell:

    An electrical circuit needs a good ground to function correctly. A bad electrical ground may affect one or more electrical systems because it forces current to search for other easy paths back to battery ground. This may cause all kinds of trouble for lights, sensors, modules and other electrical and electronic components.

    Causes and Symptoms of Bad Engine Grounds
    Bad engine grounds may be caused by:
    •Loose, rusted or damaged ground terminals or wires
    •A loose, damaged or corroded ground battery terminal
    •Poor component installation or repairs

    Symptoms of a bad engine ground may include:
    •Dim lights
    •Flickering lights
    •Electrical devices working erratically
    •Faulty fuel pump
    •Slipping or burned out AC compressor clutch
    •Intermittent failure of sensors
    •Damaged throttle or transmission cables
    •Hard starting
    •No-starting
    •Dead battery

    Often, bad grounds are relatively easy to diagnose and fix, usually in minutes. You can diagnose and make the repair in your own garage using just a digital multimeter (DMM) and some common tools. If you don't know where all the engine or transmission grounds are located in your car, you may need to consult your vehicle repair manual. You can get a relatively inexpensive copy through Amazon. Haynes manuals come with step-by-step procedures for many maintenance, repair, and troubleshooting projects. So you'll get your small investment back in a short time.

    OK. So get your multimeter and let's find those bad grounds in your vehicle.

    I. Diagnosing Electrical Grounds
    The following sections are divided between "engine ground" and "body ground" tests. This will make it easier to test the starter motor ground path and accessories grounds to find common electrical system problems.

    Here are a couple of important points to keep in mind when troubleshooting grounds in your vehicle:
    •When checking ground connections, make sure the terminals attach to a non-painted surface. You want to connect to bare metal. Paint, corrosion, greasy surfaces, frayed or broken wires, and loose connections are the main cause of bad automotive grounds.
    •Some vehicles use a separate body ground wire, besides the main ground (black battery cable), that runs from the battery negative terminal to the chassis. This is for the headlights, accessories and other electronic equipment.

    II. Checking Engine Grounds
    The engine ground provides an electrical return path for the starter motor. A bad engine ground is a common problem leading to hard-starting and no-starting conditions. The following test takes a voltage drop reading to locate unwanted resistance in the engine ground path.
    1.Disable the ignition or fuel system to prevent the engine from starting during your tests.
    If the ignition system is equipped with a distributor, you can disconnect the high tension cable from the distributor cap and ground it to the engine (bolt or bracket) using a jumper wire. On other systems, you can remove the fuel pump fuse. Consult your car owner's manual or vehicle repair manual to locate the fuse. You can also use a starter remote switch. Connect the switch to the control circuit terminals on the starter relay or solenoid.
    2.Set your DMM to DC Volts and choose a range as close as possible, but grater than, battery voltage. For example, 20 volts. Or choose the autorange function, depending on your particular multimeter features.
    3.Connect the meter's red lead to a clean surface on the engine, and the meter's black lead to the negative (-) battery post.
    4.Have an assistant crank the engine for about five seconds, just enough to get a good reading. You should get a reading of 0.2 volts or less. Consult your manufacturer's specifications in your vehicle repair manual, if necessary. Did you get a higher reading? There's some unwanted resistance in the ground circuit. To locate the problem, continue with the next steps.
    5.Move your meter's red lead to the main ground terminal, engine end side.
    6.Have your assistant crank the engine while you take a voltage drop reading.

    Repeat the previous two steps, moving your red lead to the terminal that connects the black, main ground, cable to the battery post. When you get a reading of about 0.2 volts or less, the unwanted resistance is located between this and the previous test point. Check for corrosion, broken or loose wires.

    III. Checking Chassis Grounds
    Electronic modules and many electrical components on the engine, transmission and passenger cabin use the chassis or firewall as an electrical common ground. This test checks for unwanted resistance at these points, including the secondary ground path between the battery and chassis, used by some older models. If necessary, consult your vehicle repair manual.
    1.Connect your meter's black lead to the battery ground post (-), and your meter's red lead to the firewall.
    2.Have an assistant crank the engine for a few seconds.
    You should get a voltage drop of 0.2 volts or less. If the voltage drop is higher, continue with the next steps.
    3.Move your meter's red lead to the terminal on the firewall end of the secondary ground wire. Take a voltage drop reading. If you get a reading higher than 0.2 volts, go on to the next step.
    4.Move your meter's red test lead to the next terminal, connecting point, following the path back to battery ground. Take a voltage drop reading at each point.
    When you get a reading of about 0.2 volts or less, the unwanted resistance is located between this and the previous test point. Check for corrosion, broken or loose wires. Also, check voltage drop across ground straps that connect the engine to chassis, and the engine to the firewall.

    IV. Checking Transmission Grounds
    Transmissions on some vehicle models come equipped with chassis and/or firewall grounds for modules, sensors and solenoids. You can also check these grounds using your DMM.
    1.Check voltage drop between the transmission case and battery negative post. Voltage drop should be 0.2 volts or lower.
    2.Check individual chassis grounds by taking a voltage drop across each ground strap on the transmission. Voltage drop should be 0.2 volts or lower.
    Clean, repair or replace transmission grounds as necessary. Remove grease, rust and paint from under ground terminals, or replace damaged ground straps.

    Common Voltage Drop Values
    Across a connection 0.00 volts
    Across a wire or cable 0.2 volts

    V. Why It's Important to Find and Fix Bad Grounds
    Bad Engine Grounds can ultimately prevent the battery from charging properly, the car computer from getting the correct signals, cause the headlights from illuminating properly or at all, cause hard-starting issues and other faults.
    Even more, bad engine grounds can also cause damage. If too much current tries to find proper ground unsuccessfully, it will choose an easy path through transmission components, transmission cable, throttle cable, wheel bearings and narrow ground wires, causing severe damage to these and other components. Whenever you see signs of electrical failures, check your engine grounds.
    The diagnostic tests outlined here are simple procedures you can conduct using a digital multimeter. And they'll save you time and money in a few minutes.

    source: https://axleaddict.com/auto-repair/B...-and-Diagnosis

    These are 2 of numerous very simple ways to explain it (copied):

    Essentially, a "ground" is an electrical connection to a common return in circuit. In automotive terms a ground is a connection to the body or other metal surface of the vehicle. The body is connected to the negative terminal of the battery. Thus any connection to the body of the car is a connection to the negative terminal of the battery. Electricity flows from the positive of the battery, through the circuit to do some work, then back through the body to the battery . This is a "negative ground" system which is by far the most popular automotive ground scheme used in the automotive world.
    The main reason this is done is to greatly simplify the wiring of a vehicle. Since most car bodies are made of metal (at the very least almost all frames are) they provide a perfect ground plane, eliminating the need to run a separate ground wire to each circuit which almost chops the amount of wire necessary in half.

    Good grounds are important because poor grounds cause voltage drop. The consequence of this voltage drop is that the systems in that circuit can malfunction. How do bad grounds cause voltage drop? Well, the answer is Ohms Law.
    Ohm's Law states that V=IR. This means that the voltage drop (V) is proportional to the current through the circuit (I) and the resistance (R) of the resistor (or bad ground in our case). An easy example is attempting to draw 10 amps through a bad ground with a resistance of 1 Ohm. So V=10(1) thus making the voltage drop a whopping 10V. This leaves only 2 volts available (in a standard automotive 12V system) to power the circuit and means that all that extra power must be dissipated as heat at the resistor (bad ground). Generally this heat makes the condition even worse, causing more voltage drop and more heat. In the most severe cases the ground will function under light loads yet fail under high current draws causing what appears to be an intermittent failure. Many people have seen this behavior caused by a loose (high resistance) battery terminal.

    Bad grounds can cause poor performance in almost any circuit. Voltage drop can manifest itself as dim headlights, one circuit malfunctioning when another is switched on (a common symptom is that the heater blow slows and dash lights dim when the brake pedal is pressed) and all kinds of other random weird issues.
    ----------------------
    a. Every electrical component in you car, even a light bulb, has to have a negative and a positive connection to the battery for it to work. The negative pole (-) of your battery is connected to the chassis of your vehicle, and this is the ground you are referring to.

    b. Lets say that you have a lightbulb in your car. For this lightbulb to energize (turn ON), it must be connected to both the positive and the ground side of your vehicle. Remember that the negative pole is connoted to the chassis of you vehicle, and that this chassis is the "ground" side.

    c. So, one lead or wire is connected to the positive side of the battery, and the other lead is connected to the vehicle's chassis. However, since the metallic frame (ribs, etc.) of your vehicle is grounded to the chassis, you can have grounding points throughout the vehicle. Even the motor is grounded to the chassis via a grounding strap. The electricity that powers all of the electrical components in your vehicle travels out the positive side of the battery, through each electrical component, then through the chassis and ground points, back into the battery through the negative pole.

    d. If a grounding strap, or any grounding point is loose, the electrical components affected can't work because the circuit is broken (open). In your case a "ground problem" could be a loose, or corroded, or broken ground wire or grounding point. Since the ground lead (wire) usually has a wire terminal, check this terminal to make sure it's clean and secure on the grounding area.
    Last edited by shogun; 06-24-2019 at 12:13 AM.
    Shogun tricks and tips for the E32 series are HERE!

  2. #2
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    and here another "nice" example of a bad ground cable between engine and chassis, check them, your car needs good ground cables
    Attached Images Attached Images
    Last edited by shogun; 10-28-2019 at 08:51 PM.
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  3. #3
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    I made a new ground cable with some wire designed for wind farms, welding cable crimp connectors and a welding cable crimp tool.
    Attached Images Attached Images
    1989 750iL schwarz/schwarz
    1991 M5 schwarz/silbergrau
    2013 328i coupe diamondschwarz/caramel
    2003 525iT orient blue/tan
    1990 535i/5 schwarz/schwarz

  4. #4
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    Another bad ground problem solved, quote: After realizing I am getting no fuel, I measured the voltage at fuse 23 and the fuel pump connector, was only getting 10v while cranking. Removed the fuel pump assembly, everything looked pretty good in there, just to make sure re soldered the common ground connector for both fuel pumps. Re installed the fuel pump assembly, applied 12v, both fuel pumps fired up happily. (did not test with 12v direct before removing, probably should have.)
    Re connected fuel pump connector, started the car. Fired up on half the turn! Ran smooth as always. Measured voltage at fuse 23 and 22, both getting a very happy 13V.Re started the car bunch of times, every time fires immediately.

    My 850 is dead in the water, no spark! https://www.bimmerforums.com/forum/s...water-no-spark!
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  5. #5
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    Do you know by chance where is located negative big black cable of the battery to chassis ground ? Thanks ! I am pretty sure after the fusible link cable goes to the left side to the general module side. Is that big black cable goes directly to the starter or alternator or B+ post next on the left of heater valve or this big black cable a touch to the chassis ground some where under the carpets.

  6. #6
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    the short cable from battery to the base of the rear seat = chassis, you can see in front of the passenger rear seat base a plastic cap, remove the cap and then you see it.
    Battery cable negative 12421719713 L=860MM https://www.ecstuning.com/b-genuine-...e/12421719713/
    pics where it is located and connected
    http://edv-kasse.de/bmw/batterie/P6100138.JPG
    http://edv-kasse.de/bmw/batterie/P6100139.JPG
    http://edv-kasse.de/bmw/batterie/P6100140.JPG
    Last edited by shogun; 06-25-2020 at 06:34 AM.
    Shogun tricks and tips for the E32 series are HERE!

  7. #7
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    As I understood the main ground connection will be between engine and chassis. Which could be tested by voltage drop test.

  8. #8
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    There are plenty of ground cables/points all over the car besides the battery ground and the engine ground, all over the car, you can see them in the ETM. See page 0672-00 to 0672-28 ground distribution http://shark.armchair.mb.ca/~dave/BMW/e32/e32_90.pdf
    what X165 etc means you find in the section 7000-00 component location chart and 7100-00 component location views, example: X165 ground, location below LH side of dash, left of steering column, page 7100-32-01.
    It helps to study the wiring diagrams and read thru all the pages. Understanding European wiring diagrams file print out/download from here http://www.e38.org/e32/ in section electronics
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  9. #9
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    another example: Car shuts off while driving..... https://www.bimmerforums.com/forum/s...2#post30518432
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  10. #10
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    Ground cable one side a touch to car chassis and another one to engine ground bracket is aluminum and engine itself iron cast have any one clean connection between bracket and engine block I think ground problem also there exists ?

  11. #11
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    yes, all contact surfaces must be clean to have good contact and also the wire itself.
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  12. #12
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    Don't forget the valve cover ground strap, at least on the V8s though others may have something similar. All of the coil packs on each bank share this common ground and this extra important since the valve covers sit on rubber gaskets.

    https://www.realoem.com/bmw/enUS/par...&q=11121736201

    screen-grab- 2021-02-18 at 10.33.01 PM.png
    I have wrenched on vehicles with:

    1 cylinder
    2 cylinders
    3 cylinders
    4 cylinders
    5 cylinders
    6 cylinders
    7 spoke wheels
    8 cylinders

  13. #13
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    Contact surfaces must be clean to have good contact and also the wire itself if bad you can clean and keep it contacts clean that won't help. The wire itself needs to be change to brand new wire with conectors on both ends.

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