M30 Crank, No-Start Fix: Fuel Supply … In-Line, Main Fuel Pump

After isolating fuel supply as the cause of the no-start condition on my M30-engined 1984 BMW 633 CSi, we removed the cradle that holds the main, inline fuel pump and the filter, both.  These are located on the passenger side near the rear wheel, underneath the car.  Getting the cradle out is a little tricky, even after the 10mm nuts have been removed. Some wiggling and jiggling helps.

We removed the fuel pump from the cradle and we bench-tested the pump.  Sure enough, it was bad.

We removed a unit from another BMW, and we bench-tested that too. It worked. That pump went into the cradle, and the hose to the fuel filter was attached next. The cradle went back into the car, and the fuel lines and electrical connections were hooked up.

Even so, the car didn’t start. So, we split the problem into fuel pump and supply vs. wiring to the fuel pump.  We hot-wired the fuel pump with a separate, stand-alone battery, with positive hooked up to the green wire, and negative hooked up to the black wire. The pump started buzzing, and the hose that we’d removed from the fuel rail started spurting fuel, into a cup that we’d optimistically pointed it to.

We disconnected the stand-alone battery, and inspected the hose to the fuel rail. It had started deteriorating but not terribly. So, we cut off 1/2″ or so, and the hose could still reach without being overextended.

The next challenge was to get the hose all the way onto the fuel rail.  It’s a tight fit, and it’s hard to shove the hose all the way on.  Yet, neglecting this can make the hose come off, which will cause the car to not run, and it might well cause an engine compartment fire too.  So, I heated up a cup of water, and stuck a plastic bag over the end of the hose, and stuck the hose and bag into the hot water, to make the hose more pliable. This helped. I removed the hose from the water and the bag, and slipped a new hose clamp around the hose. I shoved the hose onto the fuel rail as hard as I could. When it didn’t go far enough, I poured some more hot water directly onto the hose, and tried again.  Finally the hose was pushed up against the main fuel rail as far as it could go. I tightened the hose clamp. The system had integrity again, yay!

I reattached the separate battery, and I could hear the pump going, and fuel being pumped through the fuel rail and back into the tank. I liked being able to do this without the added noise of the engine being cranked over, and I liked being able to walk around and inspect the various fittings for leaks.  I found none.

Finally, after convincing myself that things were in order as to the fuel supply, I hooked up the car’s main battery and I cranked the engine. The car started. 🙂  Yay!

Next, I get to figure out why the fuel pump isn’t getting power … but meanwhile, even if I have to hot-wire the fuel pump, I at least have a drivable car again.  Better …


M30 Crank, No-Start Troubleshooting: Fuel Supply

My 1984 BMW 633 CSi (with the M30 engine) refused to start one day. Over the most recent few weeks, the fuel pump had become progressively louder, and that had been my cue, but I’d chosen to ignore it.  Finally, something broke.

Had I not suspected the fuel system, I would first have tried to start the engine on starting fluid, and if it started then, I would have concluded that the fuel system was the problem.  But, I had my suspicions as to the latter already.

I like to split fuel system problems into fuel supply vs. everything else. To test the fuel supply, I pulled the hose off the fuel rail, towards the back of the engine compartment. I made sure there was plenty of fuel in the tank, and then I used the key to crank the engine. No fuel came out the hose.  That told me the problem was with the fuel supply.




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 1984 BWM 633 CSi.”
“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.”
“Well, I don’t have it.”
… and it doesn’t get better after that.

Assuming the person does have the VIN, the next conversation goes something like this:

“How much for the alternator?”
“Say, what?”
“For the alternator?!”
“Wow! The entire car cost me maybe $2K and that had a working alternator. That’s crazy.”
… and it doesn’t get better after that.

I’ve gone shopping for aftermarket spark plug wires. The dealer prices were astronomically high, and when I tried aftermarket, I still ended up being quoted something like $400 for a set of seven wires. Forget that, I thought, 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 E24 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 E24s and we’re trying to keep them going, with a tight budget. We empathize.

My little used parts business is not the world’s smartest when it comes to E24 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 own a sad fleet of half a dozen floundering E24 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, an almost- 30-year old car 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 we used a mangled coat hanger to work the throttle on our 1988 BMW 635 CSi. 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 6seriesparts.com because you’re dealing with someone who “gets” you.

E24 Fuel Pump Interchangeability

I just removed the main fuel pump from my not-very-happy 1985 BMW 325e E30.

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 as contemporary cars with the M30 engine, i.e., the 5, 6 and 7 series. 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.

Time will tell. 🙂

Fuel Pump Blues

The fuel pump on my my 1984 BMW 633 CSi had progressively gotten more and more loud recently, but I ignored that. I drove to my fenced storage sheds in the middle of the night to get something out of there, and when I tried to start the car, it wouldn’t.

Getting out of there was interesting since the place has high fences, and the exit door opens when a car approaches it. It took some Jackie Chan moves for me to actually get out. Later, I towed the car to my office, and checked … the fuel rail has no pressure.

I prefer working on parts while they’re on my warm, clean workbench, as opposed to underneath the car. So, I removed the fuel pump from the car.

The pump and filter are mounted on a plate that locates them together. To remove the plate from the car, loosen the two 10mm nuts at the back, and the nut at the front. Push the front bolt in, and then slide the plate out of its rear mounting. This gives you some flexibility that helps you get to the two electrical connectors on the actual pump. To get to them, slide the covering electrical insulation hoods down, and then use sockets or wrenches. The two nuts are not the same size. As I recall, one is 8mm and one is 7mm. Then, loosen the 8mm bolt that affixes the clamp that locates the fuel hose so it doesn’t pull loose from the filter. Undo the clamp for the fuel line that goes into the fuel pump, and the clamp for the fuel line that goes into the filter. Now, you’re ready for your gasoline shower, and you realize you should have put on gloves on each hand, and brought a larger drip try, and wow, the splashes travel far. Blink often.


I drained the filter (by turning it into all sorts of positions so the fuel spills out) and then separated the fuel pump from the filter. When you put the filter down on a workbench, be aware that some fuel might still leak out.

Away from the worst gasoline fumes, I touched two 12V leads, one + and one -, to the two electrical connections on the fuel pump. It made a spark and there was a sort of jolt but no sound like a pump going. So, this means it’s a bad fuel pump.

A new unit is more than $100, and it’s not just about replacing the main fuel pump. Often, its failure has a root cause that’s the failure of the transfer fuel pump that’s located in the gas tank and is supposed to help reduce vapor lock by keeping the fuel inside the fuel line under pressure at all times.

Some say that when the in-tank pump fails, the main fuel pump basically overworks itself. If that’s true then replacing just the main fuel pump is thus false economy.

A New Business Model for Owning an E24

This idea might be of value to you if you own, or want to own, an E24 car.

Part-time, I sell used parts for 1980s BMW cars. In the process I sometimes have the opportunity to buy a good-deal car, so I do. I tend to hang onto such cars for many years in the interim. For example, this one I’ve owned for more than 10 years but now it is for sale.

Often, the person who buys a car like this has owned one in the past, or owns one currently. For many people, the decision to sell a car like this means a lost battle against expensive repairs. As someone who owns several of these cars, I know. That’s what inspired me to start my part-time BMW-used-parts business. I needed a steering rack for my E30 and it was going to cost me $400+ just for the part.

If you own a car like this, perhaps in the last year or two you’ve spent $500 on a new exhaust, $300 to get the interior improved, put new tires and brakes on the car for another $900 and so on. And now the transmission is going out or you’re facing some such expensive new problem.

You are upset not just because you finally have to admit defeat and let the car go. You also don’t like how you sunk all that money into it for parts that are now going to go away. At most you’re going to get a couple of hundred bucks for the car in its present, damaged state.

Here’s my proposition: trade in your car for mine … and mark your new parts with special paint, and tell me what they are. I’ll transfer these valuable-to-you items from your car to mine. And, I’ll include some sort of peace-of-mind warranty since my mechanic is savvy about working on these cars plus I have a stash of used parts. So, you end up driving the same kind of car you used to drive, but now it’s covered in case something big breaks, plus your investment in parts was carried forward from your old car to the replacement one: the new exhaust, the interior, the tires and brakes … whatever you value, gets moved from your old car to the replacement car as part of the deal.

If you like this idea, please let me know what you have vs. what you’d like. Many of these parts fit multiple models, so if you have an E28 and you want an E24 instead, many of your high-value parts will move across.

Fixing a No-Crank Condition on an Automatic BMW 635 CSi

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 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.

ZF 4 HP-22 Automatic Transmission

For its time this transmission was very advanced. It was a four-speed automatic transmission in an era when this was highly unusual.

It also has a lock-up torque converter. This feature means that, at 60 mph or so, the automatic transmission starts to behave like a stick-shift transmission. This helps power and fuel economy, both.

This transmission is light yet very strong. It is also very durable. It has a long life-time especially when serviced fairly regularly. Fortunately, it has several design features that make it easy to service.

BMW didn’t make this transmission; it was made by arguably the world`s leading manufacturer of automatic transmissions, a German company named ZF.

This transmission was used in the flagship models of elite automakers such as Alfa Romeo, BMW, Jaguar, Land Rover, Maserati, Peugeot and Volvo.


The EH variant of this transmission has some special electronics that enabled the car to have an economy mode or a sport mode. A knob by the gearshift lever enables the driver to change the car’s personality from docile to fire-breathing.

M30B34 Engine


The M30 engine was made in many sizes. Approximately, these included: 2.5 liters, 2.8 liters, 3.0 liters, 3.3 liters and 3.5 liters.

The M30B34 engine is (approximately) 3.5 liters (though it’s closer to 3.4 liters, technically.)

Due to its larger displacement, it tends to more powerful.

The North American version has an 8 to 1 compression ratio, which is very low. This makes it very forgiving as to what octane gasoline it can burn.

This particular engine also has exceptionally good internal coolant flow, better even than the M30B35 engine that superseded it. All other things being equal, this makes it more reliable.

M30 Engine


Here are ten reasons to like the M30 BMW engine.

1. Designed in the 1960s, this engine helped make BMW highly respected for its engines’ quiet operation, power, economy, reliability, durability, smoothness and cleanliness. A noted automotive journalist declared it “the best 6-cylinder engine in the world” at a time when BMW was relatively obscure and its competitors included Jaguar and Mercedes-Benz. This engine is one of the main reasons why BMW has become a household name.

2. BMW used this engine from the late 1960s to the mid-1990s in its most elegant and pricey models. Its basic structural elements made it simple and advanced when it was introduced, able to be competitive for 30 years. This spanned a time-frame when most automotive engines were superseded by fundamentally different models due to the difficulty in keeping up with ever-more-stringent US clean-air regulations. These measures became more draconian year after year, faster than refinements on lesser engines could generally keep pace. For example, in the late 1970s, when other automakers needed to resort to expensive and complicated components, this engine was so clean-burning that it didn’t need such additional clean-up measures.

3. In an era when many other engine designs used internal plastic parts, this engine used metal. Where other engines use internal belts, this engine uses metal chains. This design approach makes this engine exceptionally reliable and low-maintenance.

4. It is also durable: many of these engines last for 250,000 miles or more. At that point, if it needs an overhaul, only the top half typically does. The lower (main) section can be good for half a million miles or more, before needing an overhaul.

5. Maintenance costs are low due to the parts being logically laid out and easily accessible. Parts need replacement rarely due to being so high-quality as to design and materials. This engines has been used so pervasively that parts for it are affordable and easy to find, at the dealership and even in a small-town chain store.

6. Though powerful, this engine is quiet and smooth.

7. It is also fuel-efficient , unusually so especially for such a powerful engine.

8. BMW made the basic engine but the company chose to outsource the fuel injection to the world’s leading manufacturer of such parts: a company that also supplies parts to Alfa Romeo, Audi, Mercedes-Benz, Porsche and Rolls-Royce.

9. Its aluminum components make the engine light yet strong. This same engine can be modified to produce much, much more power, and BMW cars raced very competitively as such. for many years.

10. The one situation for which the engine was designed to not be strong is: a major collision. Its light-alloy structure takes the impact and self-destructs, rather than passing the energy on to the occupants of the vehicle.