Fixing a No-Crank Condition on an Automatic BMW 535i

My 1986 BMW 635 CSi has an automatic transmission and it recently failed to crank (turn over when I tried to energize the starter). Then, it would crank (and start) when I messed with the gearshift lever, and then it would fail to crank (and start) again.

The relevant parts of this car seem identical to a 1987 BMW 535i that I owned until recently, so what’s true for the 6-series is probably helpful to 5-series owners too.

The culprit was a loose connection. Wiring from the car runs to the gearshift selection unit via a plug, and if that plug is too loose, the car won’t start. It is difficult to push the plug in all the way, but it helps if you remove the ashtray and vertically pull the console up as high as it’ll go. Even a tiny bit of vertical movement can make the difference you need.

As part of troubleshooting the issue, I undid the plug completely and fed it out of the ashtray hole. The wires are long enough that I could plug it into a spare gearshift selector that I had handy. When I put that unit into Park or Neutral, the car started and otherwise it didn’t. This told me that the car’s wiring wasn’t the problem, and that the problem was the gearshift lever mechanism in the car, or the connection thereto.

The way the wiring works is interesting. A starter relay makes or breaks a connection in the main starting circuit. The gearshift lever basically intercepts the relay’s path to ground. The electrical plug to the gearshift lever has nine holes. The brown-and-black wire goes into the top center hole, the one with the bubble-shaped side as opposed to the smooth sides.

If you ground that wire, it has the same effect as putting a well-functioning gearshift lever into Park or Neutral. At least that’s a good short-term fix if you’re stranded.

If you need parts for any of this, I sell them, but perhaps all you need to do is make sure the plug is tight. Normally, it’s a very tight fit so it’s unusual for it to be loose.

Power steering blues

Power steering blues … I relate personally, and I gather many people do.

A friend of mine used to pour so much power steering fluid into her car that the price started to be a financial problem even if she could ignore that the leak was so massive that she was dripping power steering fluid all out over the roads while driving. She finally handed over the car to a junkyard for almost nothing, and the power steering leak was the main reason.

My own 735i has a massive power steering leak. I’ve just been ignoring it and driving it with the power steering inoperative. I gather many folks do that. Can you relate? It’s certainly good exercise.

But, having just spent literally all night messing with a problem on an E30 with the M20 engine, I’m now very familiar with that general geography of the car. The power steering pump, which is often the problem, seems to be a big, messy, black hunk of oil.

It’s intimidating, isn’t it?

And yet, on cars with the M20 engine (e.g,, 528e model) this part is relatively easy to access, and to remove and replace.

The pump is at the extreme bottom of the driver’s side of the engine compartment, and working from the bottom, it’s a relatively simple process to remove it. A key tip is to loosen the lines before loosening the bolts that attach the unit. If you have 12 mm, 13 mm and 19 mm wrenches, you’re off to a good start.

I sell good used original BMW power steering pumps, and I will refund your money and shipping if the part doesn’t work right when installed. You’re taking a chance on a unit that might have a year’s worth of life remaining, or another twenty years. I price the part so that the risk tends to be worth taking.

Sadly, the pump isn’t the only place that can leak. The steering rack can, too … and that’s a much bigger project.

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 E12 5-series car (528i, 530i) or E28 (533i) with a tired engine.

You would LOVE to upgrade 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.


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 E28 5-Series 528e with the Super Eta engine ECU Alternate Vendors

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

We sell good, original BMW, used E28 ECU units. The price is $160 plus shipping for the Motronic 1.1 Super Eta 1988 units.

According to one official source catalog, the BMW price for this would be upwards of $1,400 for a unit. Whoa!

A Europe-based vendor is offering new units for 226 Euros. Today, that’s $293.

Some of the mass-market sellers such as eBay or on BMW forums have good prices too … how reliable they are, I don’t know.

It’s probably safe to say that our used units are price-competitive.

BMW E28 5-Series 528e with the Super Eta engine ECU Removal and Re-Installation

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

The E28 528e ECU is located above the glove box. Open the glove box, and for better access, also loosen the two straps from which the glove box hangs. Where the straps attach to the glove box, the black plastic fasteners for the straps can be pushed out by hand to some extent, and a flat-head screwdriver can help coax them out the rest of the way.

The wiring harness that feeds into the ECU ends at a massive plug that is held into position by a spring-loaded clip and a stay. The stay is attached to the ECU with two tiny screws that are too small for a normal screwdriver. A tiny flat-head screwdriver is needed to loosen or remove the stay so that the plug can be freed.

The plug and cable obscure two of the bolts that attach the ECU to the metal plate above it. Two other, non-obscure bolts also have to be removed.  They are all 10 mm bolts, and they point up.

When working on this sort of thing, it tends to be a good idea to have the battery undone, but when you reconnect it you’ll also have to re-enter the security code for the BMW factory-installed sound system, if you have one.

Dropping the ECU can kill it, so it might be a good idea to have some sort of padded-bottom box to put it into when you take it out of the car, assuming it’s still good or likely to be.

Installation is basically the same as removal, in reverse … no special subtleties of which I’m aware.

BMW E28 5-Series 528e with the Super Eta engine ECU Design Difference

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

I have owned a 1988 528e, and a 1985 528e, and I wish I’d paid more attention to these cars’ differences, specific to the fuel injection. Because I didn’t, my information as such is, sadly, hearsay or second-hand — albeit from sources that I choose carefully.

The Bosch fuel injection used by the E28 528e fits the style and structure of the L-Jetronic type of fuel injection. It has an air flow meter with a swinging vane, it has pulsed fuel injection, it has an ECU and so on. What is new, on top of the fuel injection, is integrated computer-based control over the ignition aspect, too. Hence the name “Motronic” to describe this system, no longer “Jetronic.”

Wikipedia has a nice analysis that reconciles with what I have seen.  Here is an excerpt from their write-up.

Main system characteristics
  • Fuel delivery, ignition timing, and dwell angle incorporated into the same control unit.
  • Crank position and engine speed is determined by a pair of sensors reading from the flywheel.
  • Separate constant idle speed system monitors and regulates base idle speed settings.
  • 5th injector is used to provide extra fuel enrichment during different cold-start conditions. (in some configurations)
  • Depending on application and version, an oxygen sensor may be fitted (the system was originally designed for leaded fuel).

The first version of Motronic was named, aptly, 1.0 and it was used in the E28 528e models with years 1982 through 1987. For 1988, BMW made several changes to the E28 528e model. I’ve pieced together the story mostly based on the adventures of someone who tried to retrofit 1988 goodies onto an earlier model. What seemed like it might be a simple task was actually very complex.

The 1988 model has Motronic 1.1 and there is much, much more involved than swapping out the ECU. The way the system senses the position of the engine is, for example, different.  The wiring harness is different.  The engine also has, as I recall, the head from the “i” engine. Wikipedia also mentions that the pistons were different. The result was nicknamed “super eta” whereas the previous years’ models’ engine was the “eta.”  According to Wikipedia, it was more powerful by 6 horsepower, 121 vs. 127.

So, if you are buying the Motronic 1.1 unit for your 1988, great.  If you’re buying it to make a fire-breathing monster out of your pre-1988 car … maybe that’s not such a good idea. 🙂