Door Lock Issues

If your car’s door lock is failing, it might be helpful to know that the door locks are essentially identical on the E23 and E24 models from 1977 through 1986. The lock cylinder fits into the door with a complex structure that involves a tunnel at the end of the lock cylinder. Into that tunnel, we fit a tiny ball bearing, and a spring, and another ball bearing. Then, we turn the cylnder slightly, to keep these three items from falling out. We fit a spring with two tabs around the cylinder, and finally we slide in a plate that keeps it from falling out of the door.

Looking at Actual Parts, Carefully

I recall my surprise at analyzing some 3-series E30 glove boxes, and discovering that the glove boxes for cars with the later-than-Motronic-1.0 computer had a shallow notch at the inner front corner, so that the thicker fuel injection cable (three rows of pins vs. the earlier two) doesn’t chafe. It’s a very logical engineering change, and not surprising. The glove box with the notch even has a different part number.

What made this surprising is that the official BMW parts list mentions only one variation. So, by analyzing the parts, physically, carefully, in person, I found out more than if I’d just read about things online.

For a while, I tried to figure out what made some cars have the earlier-style glove box vs. not. The change seemed to center around 1987 but I couldn’t put my finger on it until I realized that cars with the older version of Motronic computer had the older version of glove box, and 1987 was the year when things changed a lot as such — but the 1987 325i cars had the newer-version computer whereas the 1987 eta-engined cars still had the older-version computer.

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This experience really inspired me to go look in person at what’s actually going on. It reminds me of when I worked at an automobile assembly plant (not for BMWs, sadly). The production control folks had recently managed a change by which cars of a particular model would be fitted with chrome tips on their exhausts. The parts were ordered, brought to the production line, and the assembly instructions were changed to tell workers to put the chrome tips on. But, at the end of it all, my job included being the reality-check person, to go see if in fact all of this planning had actually resulted in chromed-tip exhausts on cars exiting the assembly line. For me, there’s nothing as solid and reassuring as seeing something first-hand.

So, today’s project involved Mass Air Flow Meters on the M30 engine. I own a 1980 BMW 633 CSi, a 1992 BMW 735i, and several models in between, including a 1984 BMW 633 CSi and a 1984 BMW 733i. My tech and I inspected the mass air flow meters on all of these cars, and checked the part numbers. Of course, it’s possible that some of these parts were not originally on the car, but I’ve personally driven each of these cars so I know that the part at least works on that car.

Although the 1992 car has a pretty plastic cover on top of the mass air flow meter, when the cover is removed, the part is the same as on all the other models we analyzed. And so, now we have a good handle on mass air flow meters for the M30 engine.

There are still a million things we DON’T know for certain, but it’s nice to have a fairly good handle on at least this tiny part of the puzzle.

That’s the sort of confidence and certainty that we enjoy.

Fixing a “Limp Home” Mode Issue

The E32 750iL uses an electronic connection between the driver’s right foot and the throttle plate opening. No more mechanical cable.

This system is named “EML” which is an acronym for Elektronische Motorleistungsregelung which is … electronic motor output regulation. I think. German is my first language but my Oma didn’t teach me BMW tech stuff.

An EML light in the instrument panel should come on briefly when the car is started. This shows all is well. When there is a problem, the system would rather not go crazy and maybe accelerate when you didn’t want it to. So, if it self-detects a problem, it shuts down. That means the car goes into a mode where whatever your right foot does has a very minimal effect as to engine speed, bringing it from idle to barely above that, and also the transmission in “drive” mode is in third gear. This tends to enable you to get home slowly but surely, sort of like a wounded animal limping home.

As to troubleshooting: it’s either a false alarm or not. The former means that a bad EML light can actually trigger the problem. Troubleshooting this aspect is probably the easiest. The ideal is to have another good, running similar car and to swap instrument panels, and to draw conclusions from what you observe as a result. If that doesn’t make for a quick fix, you can diagnose the instrument panel. The later ones have a self-diagnoses built-in. The earlier ones require a lot more work, and the risk of breaking parts, and the need for an ohmmeter.

The instrument panel for the E32 BMW came in three versions. The first one had a gray back plate. This was used until 2/89. The second one had a white back plate.  This was used from 2/89 to 9/90. The third one had a blue back plate and that was used from 9/90 until the end of the production run.  The colors imply different internals and non-interchangeability specific to the gray back-plate, though the white back-plate and blue back-plate versions are very close. The latter two save the car data on a chip that can be moved from instrument panel to instrument panel.

Basically, our BMW 1989 750iL car is in “limp home” mode. This mode is announced by the EML light in the instrument panel not coming on. This could be due to a fault in the instrument panel, or elsewhere.

To check the instrument panel, I got another gray-back-plate instrument panel and installed it.  The problem did not go away.

Perhaps both instrument panels are bad, perhaps it’s time for me to stop suspecting the instrument panels. 

I have started dismantling the original instrument panel. There is a back half and a front half, and they hinge together. The hinge comes loose, and so I’ve split the two halves. The rearmost half, into which the EML lights fit, has a light gray plastic housing and a circuit board. I’m assuming that the component-measuring I need to do is from behind, so I need to remove the circuit board from the gray plastic housing.

I found it hard to do this. I pried loose the 4 little feet that affix each plug base to the circuit board. it loose but it doesn’t seem like that’s the right way. I’m trying to figure out how to get these apart safely.

I’m enthused about this because one of the two EML lights seems blown (black glass) and the other might be unhappy too. I’m trying to rule out electronic causes before I start unbolting expensive parts … two blown light bulbs would explain the issue away, 100%.

Next hurdle: how to remove the printed circuit board from the back plate.

I want Empathy when I Buy Parts, Dammit

The local BMW dealer parts counter guy seems to be a nice man, but … sad. I can guess why. Day after day, he deals with the following two sorts of dialog, many times a day:

“Hey, I’m looking for an alternator for a 1992 BMW 735i.”
“What’s the VIN?”
“I don’t know. I don’t have it with me. I’m at work. The car’s at home.”
“I need the VIN to look up the parts.”
“Seriously?”
“Yes.”
“Well, I don’t have it.”

… and it doesn’t get better after that.

Ironically, the parts guy (and his boss, who made the policy) is aware of subtleties most customers ignore, but will probably nevertheless be upset about if not addressed, so it’s a no-win situation for the parts guy.

I’m clear that as a 7-series parts owner, you don’t care about 3 series BMWs but the best example I know involves the 1987 BMW 3-series. Imagine you’re buying a replacement glove box. All the 3-series glove boxes appear to be identical … but they’re not, in a subtle way. The early US models came with L-Jetronic or Motronic 1.0 which has a certain number of strands in the wiring harness that runs from the engine compartment through a grommet in the firewall in the vicinity of the glove box area, to the engine management computer located above the glove box.  In 1987, some models got Motronic 1.1 which has many more strands of wiring, hence a much thicker wiring harness as such … thick enough to chafe on the inboard rear corner of the glove box, and that could damage the engine wiring harness, so the BMW engineers made a notch in the glove box at that location.

Who would have thought that a glove box is tied to fuel injection … and yet it is.  So ironically the parts guy behind the counter is treated by many customers as if he’s an idiot when  really he’s being commendably cautious.  In the customer’s defense, sometimes the VIN really doesn’t matter and the parts guy shouldn’t be asking.  It’s good to know when to ask and when not to ask.  We typically do, so that might well be another reason to buy from us.

Anyway, back to our hypothetical situation.  Assuming the customer does have the VIN, the next conversation goes something like this:

“How much for the alternator?”
“$514.34.”
“Say, what?”
“$514.34.”
“For the alternator?!”
“Yes.”
“Wow! The entire car cost me maybe $3K and that had a working alternator. That’s crazy.”
… and it doesn’t get better after that.

Aftermarket prices are often better, and sometimes not by much. Sometimes, when I heard the price, I thought “Forget that,” or some less-polite variant.

Seems to me that whoever comes up with these prices has no idea of the basic viability of someone who’s not made of money, trying to keep their E23 or E32 or E38 going. There seems to be a basic disconnect when the parts prices are so high that a customer reacts with incredulity. Basically, the vendor and the customer don’t relate to each other. They’re are not on the same page. There’s no empathy.

* * *

BMW parts prices can suck, but there’s a parallel to that: software.

How often have you used software that sucks, because regardless of how technically cool it might be, it sucks for you because it doesn’t work for you? Whoever made it didn’t empathize. As to whatever your situation was, they didn’t “get it.”

There is a better way. In the software industry, it’s called “Eat your own dog food.” Wikipedia defines it as: Eating your own dog food, also called dogfooding, is a slang term used to reference a scenario in which a company (usually, a computer software company) uses its own product to demonstrate the quality and capabilities of the product.”

It’s a great idea.

That might be the best reason to buy your used parts from my little company. What’s in it for you? You’re understood. That’s it. We also drive old 7-series cars and we’re trying to keep them going, with a tight budget. We empathize.

For a while, I’ve driven a 1992 735i whose front door wouldn’t open, so I got in the passenger door and clambered over. And, I survived. I didn’t have money for the “new parts” solution.

My little used parts business is not the world’s smartest when it comes to E23 or E32 or E38 cars. We haven’t been in business the longest. We don’t have massive depths of technical insight. We don’t have a huge inventory. We often mis-estimate the time it’ll take to get a part into inventory.

But, dammit, we relate. We have our own little sad fleet of several floundering old 7-series cars, and we struggle to keep them going on a tight budget that includes wondering how we’re gonna pay the rent this month. We get personally stranded when a main fuel pump dies, and we have to walk home and figure out what’s wrong, how to remove the bad part without causing a fire, and how to replace it without paying three figures.

This struggle makes us relate to customers who struggle, just like us.

We need to buy food, pay the rent and somehow keep viable, as transportation, decades-old cars that most people have given up on, long ago.

We tenaciously refuse to let these cars die. We make plans, we find money, and we pull through — so that we can keep driving these magnificent pieces of engineering, even if the dash lights don’t work and the heater fan is broken. At some point the way we’d just not lock our E32 because the battery was iffy and we didn’t wanna get locked out of the car due to its electric lock issues. But, dammit, we kept it going until we could figure out a better way. We’re still in the game. We’re fighting and if driving the car one more day is victory, then we’re winning.

If you like that mindset, buy your stuff from 7seriesparts.com because you’re dealing with someone who “gets” you.

1983 BMW 733i E23 Fuel Pump Information

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This picture is from a 1985 BMW 325e E30, but it’s very similar to the underside of my 1983 BMW 733i E23 that I looked at just before I looked at the former car.

On both cars, the main fuel pumps are on the driver side, towards the rear.  According to one BMW guru who advised me, and some part numbers I saw, it seems that for practical purposes, these cars use the same fuel pump. In fact, I raided my E30 so as to install its fuel pump on my E24 car, a 1984 BMW 633 CSi. As far as I can tell, these fuel pumps seem to be the same.

Removing this fuel pump from the E30 was tricky. For all the same reasons, I expect the same would be true for the E23. When it comes to fuel hoses, I can either:

  • Cut them and then replace them with new hose, or
  • Remove them and put them back as they were.

I personally have found old fuel hoses to be the cause of almost all of the fuel leaks I’ve experienced, so I now prefer to cut the old hoses off and replace them with new hoses. I make sure I get high-pressure hoses made for fuel injected systems, since I’ve had some bad experiences where a shop installed less-resilient hose and I ended up with a massive fuel leak while driving on, quite literally, the “Loneliest Road in America,” highway 50 in Nevada.

Another reason why I prefer to cut and replace is that it’s a pain to remove old hoses gently. They tend to have become hardened and tricky to remove.

Regardless, I didn’t like how short the hose is, between the disk-style fuel filter and the main fuel pump, in the picture. Cutting through this hose is difficult because I’m at risk of cutting into the metal of either the filter or the pump, and by then I’ve cut enough hose to cause fuel to leak … and metal on metal tends to make for sparks, and sparks plus fuel can mean a fire, with me maybe ending up dead, or wishing I were.  So, what seemed like a simple task was actually potentially dangerous, in this case.  I personally stopped cutting once I realized the danger, and I weakened the rubber hose and then yanked on it hard enough to essentially tear it apart.

I dimly recall that later vehicles have a different style fuel filter. The later unit is longer, and sits parallel to the fuel pump and even looks somewhat like it, essentially a metal tube of the same approximate girth and length.  The placement is also more inboard. That should simplify things.  So, it’s only on the earlier cars that this sort of placement makes things more difficult.

 

E32 Windshield Story

My 1989 BMW 750iL has had a horrible crack in its windshield for many years. And, then the EML light failed while the car was parked outside in exceptionally cold weather. This meant a “no start” condition. I tried to find a replacement part, but it took too long a time.

As the days went by, the battery gradually went flat. Meanwhile, the doors were locked. Being electric locks, the flat battery meant that I could no longer unlock the doors.

I’m aware of the trick where one pulls the door handle up “just so” while turning the key, but I didn’t want to stand outside for 30 minutes in the (literally) freezing cold trying to get that to work. So, I decided to solve both problems at the same time: the broken windshield and being locked out of the car.

I took out my safety glasses and a nice big 30mm wrench, and I put on some safety gloves. I proceeded to then methodically beat a hole in my BMW windshield. This sounds a lot easier than it actually is. Even with a pre-existing crack, these windshields are tough! It took me a long time to break through.

It probably also earned me the “toughest girl in the neighborhood” award.

If I am ever threatened by someone who wants to attack me while I’m in my car, and they try to beat my windshield in with a baseball bat, I now know that I will have enough time to park the car, pop in a CD and listen to half of an entire three-minute song before I would need to do something about the problem.

Back to my project: I finally made a large-enough hole near the passenger side since I wanted to minimize the amount of glass splinters on the driver side. I was then be able to reach the passenger side door knob, and I pulled it up. I opened the door and pulled up the driver side door knob next.

With the EML light still dead, I couldn’t drive the car so I trailered it to Low Price Auto Glass in Sparks, NV. They did a good job of replacing the windshield, parts and labor, for $195. I was tempted to try a used windshield instead, and were this an E28 car, I would have. But, on the E32, the windshield is glued to the car, thereby contributing to the car’s structural strength, and so removing a windshield from an E32 without cracking it is very, very hard. I once watched a seasoned auto glass installer attempt this, and fail.

So, now my 750iL has a nice new windshield. Better. 🙂

M30B35 Engine for sale, complete, with all electronics

Wikipedia says:

IMAG5880The BMW M30 … is a straight-6 SOHC piston engine which was used over a 28 year lifespan over many BMW models. Ward’s have rated the M30 as one of the “Top Engines of the 20th Century”.

Perhaps you own an E23 7-series car (730i, 733i) with a tired engine. Perhaps you own an E32 750iL in great shape but the engine has failed.

You would LOVE to change to a well-running 3.5 liter M30 engine with the latest Bosch electronics. Your older BMW would have a new lease on life.

There is an undeniable cool factor, too. The newer Bosch engine electronics don’t just have the latest updates but they also look more high-tech. Imagine you open the hood of your 1970s or early-1980s BMW, to show a friend. Inside is something that is NOT period correct … ooh. Wow, what IS that?

Perhaps, on your car, the engine lacks power by now, or is smoking, or needs major work. Instead of repairing, maybe it makes sense to upgrade. The late-model M30 engine would give a tired car a new lease on life and you would enjoy “sheer driving pleasure” again.

In both of the above examples, the newer M30 is likely to bolt right in with minimal or no modification. Yay!

* * *

Let’s analyze the engine-swap process cynically. Imagine someone buys a newer M30 engine plus a basket of parts, and hooks it all up. Mechanically, it might be perfect. Electronically, something might well be wrong. And, the many possibilities don’t make this a simple problem. Your delight at the simplicity of the mechanical aspect might soon be overshadowed by the hassles of the plumbing or the electronics. Could be, something is missing, or broken, or hooked up wrong. It’s hard to diagnose.

Wouldn’t it be SO much nicer and simpler to have the new engine be accompanied by EVERYthing you need to start it and run it? Instead of buying an engine plus a basket of parts, you buy an engine that’s IN a car. You turn the ignition key and the engine starts. As you move the engine into the recipient car, you test-start it every now and then to make sure things are still OK. That way, if there is a problem, you know it’s in something you have JUST worked on.

IMAG5877You get to take pictures of the way things are before you move them, and you get every fastener that’s involved.

  • No more scratching your head or looking on the Web, figuring out what goes where.
  • No more driving around trying to buy the right fasteners or missing parts.
  • No more having to special-order little missing pieces that drive up project cost and delay your progress.

Everything you need is complete, and right there. Proof: when you buy the engine, it starts.

Starting says a lot, but it doesn’t say everything. You also get to have a professional BMW mechanic of your choice do a compression test and a leak-down test.

Why a professional? Because I don’t want the spark plug threads stripped by well-intentioned but overzealous amateur folks. Once you own the engine, you can work on it yourself as much as you like. Due to my approach: as a buyer, you can buy with the confidence that I didn’t let half the Western world’s amateurs mess with the engine you end up with.

The engine comes equipped for an automatic transmission and includes the torque converter. On automatics, the throttle position sensor is more complex, so if you plan to use this in a stick shift car you will want to swap out the throttle position sensor and related wiring, and you will want to replace the torque converter starter wheel with a regular flywheel, clutch, etc.

IMAG5748The M30 as used in the 1992 BMW 735i is a powerful beast. I have owned and driven this particular donor car for many years, including at impressive speeds that my lawyer would probably advise me to not disclose. That is why I am offering this engine with such a high degree of confidence.

The Bosch electronics presume a catalytic converter, though. And, I cannot legally sell the one that came with the engine. It’s against Federal law for me to sell used catalytic converter units. How do we solve the problem legally? I officially sell you the entire donor car including the catalytic converter. You remove what you need and give the remainder back to me.

IMAG4900One of my customers recently needed the SI board that was part of an E28 instrument panel. I didn’t want to remove and sell just this part, plus there’s value to the customer in seeing it work in context. So, I sent the customer the entire instrument panel. He removed the SI board, and sent back the remainder of the parts. This donor car premise works the same way. You also don’t have to insure or register the car because you’re not going to drive it.

Why am I selling this engine in this way? I used to have a magnificently-running E32 BMW 735i and then it got more and more body damage. Then, the transmission went out.

IMAG5747I have a replacement ZF 4HP-22 transmission all ready, and I can install it, but then I still have a 7-series car with a lot of body issues. The dent in the trunk is only one example. A dent in the roof is another example. The car might well be worth more as parts.

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I have enjoyed its engine for many years, and took good care of it, so unless I’m missing something (that the tests would probably show), it’s a good, solid engine. I maintained it well, with the plan of keeping the car for many years. The previous owner took even better care of it.

I think this paradigm solves so many problems that I think this is a viable business model for my used-parts business, going forward. I plan to repeat this offer whenever next I come across such a situation again. However, to find a well-cared for engine as such from a seller / car that I know and trust … that is not all that common. And, this car is special because it’s one that I have personally owned and driven for several years.

* * *

How would this work?

  • You make arrangements with me, to buy the engine.
  • You put down a small good-faith deposit.
  • I keep the engine for you.
  • If you plan to buy the transmission too, you do the same for that.
  • Within the pre-agreed time-frame, you visit the car at my location in northern Nevada.
  • You start it and test it, and you have a professional BMW mechanic test it too if you like.
  • We apply the deposit.
  • You pay the balance the engine (and if you like, the transmission, too).
  • You also pay a refundable deposit for the rest of the car.
  • You take the car away, catalytic converter and all.
  • You work on the project.
  • You start to slowly separate the parts you need from the car, taking notes and pictures.
  • You start the engine every now and then to make sure it all still works.
  • Eventually, you have transferred everything you need.
  • Assuming it’s still in the agreed-upon window of time, you bring the car back to me (or you’re too far away, you choose to forfeit the deposit, and you donate what’s left of the car to a local junkyard).

This sale presumes that you get to help yourself to:

  • The complete engine itself
  • All the ancillaries on it such as the alternator and A/C compressor and water pump (which reminds me: the power steering pump leaks. I can throw in a better used unit)
  • All the ignition and fuel injection components including the fuel pump, fuel injection computer, and engine wiring harness.
  • Whatever else you can reasonably interpret to be in your favor as such, e.g., the radiator.

In other words, you are, by design, getting a very, very complete solution. All I expect back as to the rest of the car would be things (e.g., seats, doors, sunroof, trunk) that by no reasonable interpretation can be part of the engine or transmission or the parts that would make them work.

Do you like this approach? If yes, please contact me to discuss pricing. If you like omit the transmission, the price for the engine, and whatever it needs to work, is $1,800. If you add the transmission into the deal, the price increases by $600. The transmission is from a 1987 535i that I also personally drove.

BMW 7 Series (E32) Locked out — Electric doors, battery flat, battery inside car

If you are locked out of your BMW with electric door locks and a flat battery, my experience might help you.

I own two E32 7-series cars, a 1992 735i and a 1989 750iL. The electric door locks are a nice feature. So is the location of the battery underneath the passenger side rear seat — good for weight distribution.

Problem is, when the battery is dead, I can’t get into my car any more. Right now, after months of being parked, each car has a flat battery.

Solution 1, courtesy of BMW, is to insert the key into either of the front doors, and turn the key slowly while lifting the outside door handle slowly and simultaneously. There is a mechanical link that barely works to unlock the door, this way. This makes the car time-consuming to steal, which is good. Presumably, you breaking into your own car will have more patience than a nervous car thief. In my experience, if you mess with this approach for half an hour to an hour, you can typically solve the problem, and get into your car. Yay!

Solution 2, courtesy of physics and simple wiring, is to energize the car’s electrical system externally. On 735i or 735iL cars with the M30 engine, this is not terribly hard though it still took me a couple of hours. I jacked up the car, and placed axle stands under the outer sections of the front sub-frame. Then, I placed a jack underneath the center of the front sub-frame, just in case. I angled it so it’s not in my way as I work on the driver’s side of the car, from below. With a 10 mm socket, I removed the 4 nuts and one bolt that held the plastic pan in place below the car. This enabled me to see and reach the starter from below. Then, I used a thin-nosed, sharp-toothed jumper cable.

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I wrapped it in a pair of rubber gloves and used packaging tape so that only the very tip was exposed.

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While lying underneath the car, I was able to discern the largest nut on the starter. This has at least one large wire leading to it. With the battery charged, this is normally positive. Working from below, I grabbed this nut with the teeth of the positive-side jumper cable clamp, and then attached the negative part of the jumper cable clamp to a place on the BMW with clean metal and a good ground connection. I happened to choose the power steering bracket. Then, I attached the positive clamp of the other side of the jumper cable set to the positive pole of a good battery. The last step would be to attach the negative clamp to the negative pole of the good battery, but … what if there was a place where my insulation was weak, so that attaching the battery would result in a massive short-circuit, possibly frying the good battery and/or making it explode? To be cautious, I didn’t clamp the negative clamp to the negative pole. I just brushed it over it, barely touching, and expecting the worst. I hoped to see some small sparks but not massive fireworks. Small sparks are what I saw. That meant the BMW was drawing some current, which is good and normal. (It might have been safer yet to connect the negative to the BMW body as a last step, now that I think about it). Encouraged, I attached the clamp, and then the door locks were energized, and I could unlock the car and get inside, yay! I removed the clamps from the good battery first, and then from the ground of the BMW, and then from the starter nut of the BMW. For the 750iL I’ll probably have to make another plan because the starter seems harder to reach. At least I have the problem solved for the 735i.

Solution 3, courtesy of physics and complex wiring, works on the assumption that you can unlock the trunk manually even if the battery is flat. With a healthy battery, the trunk courtesy light would come on, meaning there is a direct connection from the positive wire of the courtesy light to the positive pole of the battery, and from the negative wire of the courtesy light to the negative pole of the battery. By energizing these wires with a charger, it’s sometimes possible to trickle charge the flat battery inside the car. The trick is that the fuse in this circuit is sensitive enough that if you simply try to unlock the doors when the system is energized with a charger, you are likely to blow the fuse, and lose your opportunity to charge the battery with this circuit. The fuse is typically #33 and it’s under the driver side rear seat and thus not accessible with the door locked. I charged the battery for about 4 hours and then tried to unlock the doors with the charger contributing some of the charge. It was risky but it worked. When attaching the jumper cables to the courtesy light, remember that it’s the large central rectangular light just inside the trunk.

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The red and white wire is the positive one. If you connect the polarity the wrong way around, you can fry the alternator diodes.

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I connected the negative jumper cable to a ground connection instead of the negative of the courtesy light, so as to have some physical distance between the two jaws of the jumper cable set.

Once I was inside the car, I yanked up the rear seat to get to the battery. I undid the terminals, using 13 mm wrenches. Then, I could remove the battery to slow-charge it or replace it. I reminded myself that on these cars, the terminal cable color are NOT the traditional “red is positive, black is negative” but that “black is positive, brown is negative.”

I hope my article is helpful. And, if you ever need good used parts for your E32, please remember me. 🙂

BMW E23 7-Series (without the EH transmission) Throttle Position Sensor Typical Problems

If you like, you can skip directly to where you can buy this part.

Perhaps the best advice as to removing the throttle position sensor is to not do so prematurely. With the unit in place, and the engine off, remove the plug attached to it, then measure the continuity between the center pin, and the two on either side. Next, ask an assistant to press down slightly on the accelerator pedal while you again measure the continuity. Finally, ask an assistant to press down on the accelerator pedal all the way, while you again measure the continuity. On some cars, the accelerator pedal and cable might be in bad shape, and it might make more sense to yank on the engine side of the accelerator cable, to simulate what your assistant might do.

If the throttle position sensor readings are different with the throttle closed vs. part-way open vs. all the way open, then the throttle position sensor is basically doing what it’s supposed to do.

A more crude yet logical-seeming check that I’ve read about is to unplug the connector at the throttle position sensor, while the engine is running. If the sound of the engine changes, it means the throttle position sensor was having an effect, which means it is basically functional as to the throttle-closed part of its function.

Although the throttle position sensor is important, my impression is that it won’t make a difference as to the engine totally failing to start or run.

The throttle cable end that is attached atop the motor rotates a shaft. Its position is sensed by the throttle position sensor. Following this logic should make it easier to locate the throttle position sensor.

The throttle position sensor attaches with two fasteners, typically screws. Its position is critical. When re-installing it, it’s a good idea to make sure that it senses when the throttle is fully closed and also when it is fully open. The resistance between the outgoing connectors can be measured, and it should change dramatically when the throttle moves to either of those two positions. With the engine not running, you should also be able to hear a slight “click” when the sensor reaches either of those two positions.

As a guideline for the new part, it might be wise to be aware of the position of the part being replaced, before it is removed.

BMW E23 7-Series (without the EH transmission) Throttle Sensor Removal and Re-Installation

If you like, you can skip directly to where you can buy this part.

Perhaps the best advice as to removing the throttle position sensor is to not do so prematurely. With the unit in place, and the engine off, remove the plug attached to it, then measure the continuity between the center pin, and the two on either side. Next, ask an assistant to press down slightly on the accelerator pedal while you again measure the continuity. Finally, ask an assistant to press down on the accelerator pedal all the way, while you again measure the continuity. On some cars, the accelerator pedal and cable might be in bad shape, and it might make more sense to yank on the engine side of the accelerator cable, to simulate what your assistant might do.

If the throttle position sensor readings are different with the throttle closed vs. part-way open vs. all the way open, then the throttle position sensor is basically doing what it’s supposed to do.

A more crude yet logical-seeming check that I’ve read about is to unplug the connector at the throttle position sensor, while the engine is running. If the sound of the engine changes, it means the throttle position sensor was having an effect, which means it is basically functional as to the throttle-closed part of its function.

Although the throttle position sensor is important, my impression is that it won’t make a difference as to the engine totally failing to start or run.

The throttle cable end that is attached atop the motor rotates a shaft. Its position is sensed by the throttle position sensor. Following this logic should make it easier to locate the throttle position sensor.

The throttle position sensor attaches with two fasteners, typically screws. Its position is critical. When re-installing it, it’s a good idea to make sure that it senses when the throttle is fully closed and also when it is fully open. The resistance between the outgoing connectors can be measured, and it should change dramatically when the throttle moves to either of those two positions. With the engine not running, you should also be able to hear a slight “click” when the sensor reaches either of those two positions.

As a guideline for the new part, it might be wise to be aware of the position of the part being replaced, before it is removed.