Hey guys, new e31 owner here, though been on the board for a few years. Picked up my 93 850ci from an acquaintance who wasn't interested in it anymore. Clean car, 93k miles that runs very smooth and only needs light mechanical and some cosmetic touch ups. Long post here so please bear with me.
The problem which sprung up out of nowhere was the car sputtering and dying on me while driving on the highway... with no shoulder... and at night. Somehow a rear end collision was avoided, don't ask me how.
I was able to determine when the car was at high electrical load (lights, air con, radio) there wasn't enough juice to keep it running. Started with the simple diagnostics, snap on modis scanner to engine obd port, fuses and relays, connections to batteries, load tested batteries and alternator, batteries checked out fine and alternator was slightly low at full load though good at idle. With no glaring problems I charged both batteries full and car worked fine for weeks, then it died again under load at night.
So this week I bit the bullet and installed a remanned Bosch alternator, new drive belts, new auxiliary fan and recharged both batteries. Install went smooth, voltage checked out, went for a drive today and BAM same issue.
I'll describe the symptoms: car starts to bog, flasher lights in instrument cluster dimly light, radio dimly lights, all exterior parking lights and third brake dimly light and warning chime for tail light out and license plate light out. Mind you this happens with the exterior lights turned off. If all electrical consumers aren't turned off immediately the car will die while driving ..... So this happens again AFTER the new alternator install. I was able to make it home by turning all electrical consumers off and keeping the car in 3rd gear to help the alternator generate more current. Once I arrive home turn car off and on, same issue. Let it sit for 5 minutes everything back to normal. What is going on here!? I can't for the life of me figure this out, I guess double the batteries means double the headaches. If anyone has any ideas on what the issue(s) could be please enlighten me, I'm stumped.
That sounds like one of the Fuseable links is failing - they are in-line with the right-hand battery cables (lots of pictures can be found with a google search). These get fractures and although they look fine they are failing.
Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i
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Check and clean all the main electrical connections under the hood. Ground from right hand motor mount to the body is especially subject to corrosion
Just replace the fusable links. I used some 80 AMP Stereo Fuzes about $15 each
One of my wrenching buddies had the same problem on his E31 850. After we changed a lot of parts like ignition cylinder, CPS etc pp., if turned out that one fusible link had a crack and apparently sometimes it still had contact and sometimes not, maybe temperature related. Changed that fusible link and all fine.
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Intersting, makes sense as the batteries do seem flukey although fully charged. Can I replace it with this BMW strip fuse?
https://www.fcpeuro.com/products/bmw-fuse-61138365901
Or are others recommended. Thanks
Fuse looks good, tiny bit of corrosion. Will replace it with this :
https://www.autozone.com/electrical-...0-rp/32381_0_0
Hopefully does the trick.
Visual inspection shows perfect and there is continuity across the fuse.. What is the best way to take it apart, drill out the rivets? I don't want to wreck the wiring or terminal ends unnecessarily.
I had similar issues- reducing the load by replacing the headlamps with LEDs solved my issue. I have not looked at fusable links...makes sense.
You only say 'fuse', and not 'fuses' - there are two of them and you have only found one of them so far!
Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i
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My E31 Repair and Information Website
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My E63/E64 Repair and Information Website
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One more note, the batteries in the car are not matched. One is a 19 date H6 AGM, the other an 18 date Group 91 Exide lead acid. Both 700+ CCA, could this contribute to the charging issues. Apologies in advance for the multiple questions.
- - - Updated - - -
I found both, the one in black box is in perfect shape. Took off nuts, inspected and checked continuity. The one under the sheathing had a tiny bit of corrosion and since riveted in cant check completely. Though continuity tested fine. I was going to change this one and leave the other as its in the box.
The AGM will not be fully charged, but if you had two of them both wouldn't be fully charged! AGM is charged to 14.8V whereas Lead-Acid are charged to 14.6V which is the voltage the standard alternator provides. Best off with a couple of cheap Lead-Acid batteries:
Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i
My BMW Repair YouTube Channel
My Current 840ci Sport Individual
My Current 650ci Sport Individual
My E31 Repair and Information Website
My E38 Repair and Information Website
My E63/E64 Repair and Information Website
Chase - Heroes to a generation
Quick update, changed both fusable links, the one in the box with a similar style link and the exposed one with a bolt in fuse. The links I took out had no visible cracks. I also noticed that the ground nut above the passenger tail light was loose, so tightened that up. So far no shutting off, which is great! But there is a new symptom, tach swinging wildly and all other gauges at zero. Could low batteries cause this.
I'll go with the loose ground nut which I assume is the negative battery ground...I went to one large lead-acid battery fwiw. I monitor system voltage at the cig lighter when running/driving to troubleshoot regarding continuing issues. I have not seen inoperable gauges etc at low voltage.
The bundled ground by the passenger taillight controls all sorts of things - including fuel pumps. So good to have that tight. This is not the battery ground, that is on the rear on driver side.
I'd be checking the other common ground failure points too... the ground strap from engine to passenger side body for one. Also, I'd inspect under the dash on driver's side to see if anyone has been fiddling in there... there are a few more common ground lugs there too.
'91 Dinan 860 Stage III (new 6L engine)
'91 Dinan 850 TT stage III (brand new engine) 21st Century Tech meets 18th Century Dinan...
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'94 850 CSi The Detroit Auto Show car (restored to factory perfect) (sold)
'96 850Ci, The George Carlin car
''73 3.0 csi, '08 535i, '03 X5 4.6is
...and a few other non BMW cars
fiddling with a ground or power without fully disconnecting the batteries can confuse the electronics modules. Try a Magic Reset and do your best to connect power in a single moment. Hopefully that will be enough to get your dash behavior back to normal.
Update: Tightened the ground by passenger tail and replaced fusable links, drove for a week and no issues. Thanks guys and im glad it was a simple issue. To the next guy dealing with this check your grounds! moving batteries in and out can knock them loose or a bonehead previous owner
Thanks for the info, in last year I posted this on the E32 forum: Diagnosing the Symptoms of a Bad Engine Ground, 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.
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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.
Shogun tricks and tips for the E32 series are HERE!
A while back I was surprised to see that there is but a single ground link from the engine-drivetrain to the car's body, I think where X446 connects to X497 (Page 0672-23) through a 4 BR/OR wire, in the 1987 ETM.
I expected that there would be several parallel connections from the engine to the chassis.
But no, all paths are insulated save for the main link. This prevents ground loops, which engineers hate!
Oil leaks, helped by gravity, can coat (insulate) undercarriage ground. I had under spec batteries, corroded wires & 2 blown fusible links on my passenger side battery with zero on driver battery. Lemon juice, vinegar and/or baking soda concoction recommended by Timm are most helpful in quashing rust.
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