Fuel problem in 1979 bmw 528i

,

@GeorgeSanJose, it definitely feels like a blockage. The air filter, fuel filter and fuel pump are all good. My suspects were also the injectors or the catalytic converter. If it is the cat, is there any chance of it starting again? It seems like if it rests for a while it can start again, but longer rests are required lately. By the way, I’m not sure if this helps, but it used to not start only in cold weather. Now it happens even when it’s 40 and above.
@db4690, the cold start valve was just replaced. As well as the thermo time switch. I think they were both probably fine, but I was grasping at straws.
Thanks for your help everyone.

The entire fuel system for the car was not designed to handle the ethanol in the gas. You should buy and use an ethanol stablizer to protect the fuel system. Stabil makes a product for marine use which you should use on every fill up.

You might have internal break down of any and all the rubber fuel lines in such an old car. The rubber actually flakes off internally and will clog anything downstream. There is no fuel cleaner that will clear it out.

The fix is expensive, disassembly and physical cleaning of all the fuel system and replacing the original rubber fuel lines with new ones compatible with ethanol.

Thanks, @uncleturbo. Just found out about how awful ethanol is for this car. Started using stabil, but currently it won’t start so I’m unable to run it through the tank.

Air meter vane? Sounds like a mechanical Venturi that moves via airflow and sends signal to computer to control injection pulses. Basically the heart of system. And $$$ and no longer made. Perhaps if you find a BMW used parts shop in Germany?

@lealea I’m not entirely sure about this, but the thermo time switch and the ECT sensor may not be the same part.

If the cat is completely plugged, at best the started engine would sputter and die, and it might not be able to start at all. But that problem is easily diagnosed, and if the diagnosis indeed proves the cat is plugged, that is easily (albeit not inexpensively) repaired.

It could be something else, but a plugged cat is a reasonably likely cause of your symptom. Before doing the cat test tho, most mechanics would recommend all the routine maintenance item suggested in the owner’s manual be brought up to date, then do ECM diagnostic code reads, vacuum, ignition analyzer, compression, and fuel pressure tests first.

One more idea. Does this car have that 70’s VW fuel injection system? I think it was called K- Jetronic or CIS or something like that. Those systems were notorious for clogging up from debris getting past the fuel filter and clogging the fuel distributor and producing this exact symptom. If your car has this VW CIS fuel injection system, and this happened soon after the fuel filter was changed, be extra-suspicious of this being the problem. It’s very easy when changing the fuel filter for the mechanic to allow debris to get into the fuel line. If this is the problem, it is easy to fix. Just ask the mechanic to take apart and clean the fuel distributor. Sounds complicated, but it is a relatively quick and easy job. Best of luck.

@GeorgeSanJose I think you might be a genius. The fuel injector system is called “L-Jetronic” and I DID just have the fuel filter changed. When these symptoms happened 3 years ago, it is quite likely the filter was changed then too. I’m not sure why it worked itself out last time? Or is it possible that it is worse this time because it happened once before? Also, is this why it sometimes won’t start? And would the symptoms be worse as the fuel gets lower in the tank? Is running Sta-bil through it a good idea?
I found a guy to work on it and we had decided to replace the catalytic converter, but I’ll run this new info by him. He probably knows, but I am curious where the fuel distributor is located. I have a Haynes and wasn’t able to figure it out. Do you mean the whole fuel line needs to be flushed out? I’ve always thought that sounded like a good idea but didn’t know if that was a thing.
BTW, once the car starts and I drive it and it warms up, I can shut it off and it will start all day long. It"s that first fire of the day – if it doesn’t start, it’s not going to until tomorrow, if I’m lucky.
Thank you so much for your info!

You’re saying it runs fine once it’s warmed up? If so, then it doesn’t sound like a fuel system clog OR a catalytic converter, those would cause problems at all times, with the engine warm or cold. There are temperature-related sensors that modify the amount of fuel injected when cold, that might be the problem.

But if your mechanic thought a new cat would cure this, even though it runs fine when warm, then I’m a bit concerned about him.

Here’s an article on the L-Jetronic system, hope it helps!
http://www.hiperformancestore.com/Ljetronic.htm

@texases I wouldn’t say it runs FINE once it is warmed up, it still hesitates up hills and upon acceleration, but once it STARTS and warms up, then it will start all day long. It started for me yesterday and today.
My mechanic was going to change the cat a my request, since we couldn’t really figure out what else to do and it was cheaper than the injectors. How’s that for logic??!!

OK, I get it. I’m thinking it has something to do with the fuel injection system and maybe the cold start operation. But this is where a good L-Jetronic guru is needed…

thanks for the link. I’ll pass it along to my guy.

@lealea

FYI L-Jetronic and K-Jetronic are not at all comparable

Totally different systems

K-Jetronic was restricted to european vehicles and is by far the more complicated system to work on.

But you apparently have L-Jetronic

I don’t have any experience w/the L version @lealea, but I had a VW Rabbit one time with the K version, and had trouble on several occassions where the car wouldn’t accelerate normally, had much less power than before, sometimes would have trouble to go faster than even 30 mph, immediately, or within a day or two after changing the fuel filter. When I took the fuel distributor apart, it was partially clogged with a sandy grit like material. This prevented the metering rod in the fuel distributor from smoothly moving up and down like it should as air flow increased or decreased past the air flow measuring plate-- which they call the “vane”.

There is an inconsistency with your symptoms tho, compared to mine. For me, it didn’t affect the ability to start the engine. It started up as normal. The problem only showed up as a very significant and noticeable lost of power on acceleration.

I’ve included a link below which explains the difference betwee the K and L systems. It appears they are similar in that they both use a wind vane to measure air flow, but the K is totally mechanical and injects fuel continuously through the injectors based on the vane position moving the metering rod in the fuel distributor, while the L seems to be partially electronic, and uses the vane position to calculate the necessary injector electronic pulse width injection. From this description, although it doesn’t exactly say so, it appears your L system wouldn’t have a fuel distributor, or if it does, is configured differently from used on the K. So my idea may be all wet.

But if this happened very soon after changing out the fuel filter, you could still have debris in the fuel lines that has lodged somewhere post fuel filter.

I’m sort of surprised you haven’t had this kind of problem before now lealea. These older fuel injection systems were an experiment in progress and are considerably more sensitive to a tank of bad gas than the new ones. The newer Toyta fuel injections systems are pretty much bullet proof compared to the versions used on cars in the 1970’s. Curious, how long have you owned this car?

Thanks for the update, @GeorgeSanJose

I’ve heard that about my fuel injectors: they were new at the time and have since been improved upon many times over.

I bought the car in May 2006 with 95,000 miles on it. It currently has 141,000 and has been my daily driver this whole time. Although I’ve put money into it here and there, I feel as though it has been a great car overall. I moved to Maine a few years ago and cars rust out here before the engine goes, so no one knows how to work on this car any more. It’s frustrating because I feel like the car has a lot left to give. I can’t help but think this is a simple problem to solve for someone who knows the car (and has access to it!). I think if all of you guys came over and drove it, you’d all figure it out!

It is possible I have two problems: the cold start issue and the lack of power and hesitation up hills. Perhaps they are unrelated.

Now I feel like maybe it’s the injectors.

@lealea I know that plugs, wires, cap and rotor were recently replaced, but has anybody actually checked for a good hot spark at the plugs?

I would also do a compression check to rule that out as a cause.

I am not seeing why a cold engine with good spark and good compression would flood rather than start.

Yes! This new guy I have took the time to check each plug for a spark.

It really feels like bad gas to me. Most definitely a fuel problem. On the drive home from work tonight it ran crappy all 20 miles. Usually it doesn’t run quite that rough. I pulled over and really revved the engine a few times and that seemed to knock it out a bit.
I’m going to run some techron through it as @texases suggested.

There are procedures available & explained in your car’s shop manual to test all parameters of your car’s fuel injection system. No need to guess or engage in magic additives or “swap-diagnosis”. It’s straight-forward to determine if the fuel and fuel lines are contaminated with dirty gasoline. The fuel pump delivery and pressure is easily measured, as well as the injector’s timed fuel volume delivery, injector to injector flow rate consistency, check valve leak down, and individual spay pattern. Likewise for the ignition and exhaust system. The only thing left is timing, which is also easily tested.

The problem is that you may run out of money before the problem is found. But that is often the way with older cars, especially ones that didn’t have a high sales volume in the first place.

I guess if this were my car I’d check the easy stuff first.

  • All routine engine maintenance per/owner’s manual up to date?
  • Good hot spark at each plug?
  • Ignition timing ok?
  • Compression ok?
  • All injectors spraying fuel?
  • Fuel in gas tank clean?
  • Timing belt/valve timing/camshaft/valve clearance ok?
  • Does temporarily disconnecting the exhaust pipe at the exhaust manifold help?

I have a suggestion for when it fails to start. wait a minute, then hold the gas pedal all the way to the floor for 30 seconds, this helps clear the flooding. Then without lifting your foot, hit the starter, it should start within one or two cranks.