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Any, but longer in cold temps. Turn the key, the starter turns for ten, fifteen seconds before ignition. Once started the engine idles @ 1500, 1800, drops to 15 within about two, three minutes depending upon the outside air temp.

What's weird is driving, the idle is the factory 1200. Or sometimes 14, picky, picky, who cares. Really weird is parking, returning within 15, 20 minutes, the car starts as soon as the key is turned. Obviously the fuel delivery system likes all of the other components to be warm, and maybe the fuel pressured up in the injectors for immediate injecting.

Any hints on what to check, in what order ? The aux air valve is working, AFM brass idle screw the same, but curious if I should be fooling with perfect tuning adjustments with both or either.

Throttle switches are right, timing is set, no perceptible missing, no fuel leaks. Get it ? On and on.

Taking ten seconds of starter turning is not right.

Fooling around,... engine off, I discovered the hose from the charcoal filter canister that connects to the fitting on the top of the manifold log making a hissing sound, obviously releasing pressure from something.

Whether or not that's causing any problems, are the the lines in/out of the old junk pot supposed to have clamps on the ends for a tight fit ?

T.Hanson wrote:
Taking ten seconds of starter turning is not right.

A couple of things come to mind, and 10 seconds is definitely not right, my first E12 fired up after 6 compression cycles, 2 revolutions, this one usually takes 9, or 3 revolutions.

My first guess is you're losing fuel pressure due to a bad check valve in the fuel pump. Hook up a gauge to the cold start injector and see what it says in the morning. It shouldn't drop, I've cut into fuel lines in junkyard cars that have clearly not run in a while and gotten a full spray from them, probably months after they last ran. The second possibility is the injectors are leaking and flooding the engine. I had that happen on an E28 where it was hard to start and would run rough at first overnight due to all the fuel in the cylinders from the injectors leaking, but that seems to be an unusual condition, even though I had it happen with several different sets of injectors on that car. But first check to make sure you still have fuel pressure overnight, there are aftermarket check valves available, you don't need to buy a new pump.

Actually something else just came to mind, you could have a leaky suction hose going to the fuel pump which would allow the fuel to drain back to the tank and make the pump work hard trying to start the siphon/pump process. Leaky suction lines can be tricky to troubleshoot and cause all sorts of problems. Hard starting, lack of power, running out of gas before you're near empty.

I seriously doubt the cold start injector is the issue, I ran with one unplugged for a while just to see and into temps into the high 20s I couldn't tell a difference starting.

I think it is common courtesy to thank you for taking the time to post your suggestions, obvious expertise from years of experience. If only time, space transport technology allowed raising my hand, in your class, with more questions.

No offense, I did the whole fuel filter, pump, lines replacement drill on my other 528, with your help. No visible pump check valve, period. Not knowing a suction line without an arrow in a parts drawing, or how to hook up a what kind of pressure gauge, where, to the cold start valve.

Too much ignorance to post for easy answers. No good deed goes unpunished, I must be off to read and learn more things myself.

Tom, you're too hard on yourself here. The check valve is built into the fuel pump, so you can't see it unless you take the pump apart. The suction line is the one going from the tank to the pump, 12MM, the only 12MM line back there. Being suction, not pressure, it can be leaky without seeming leaky, because it's leaking air into it when it's under suction. I had a problem with mine not too long ago where that line was even new, but I had a loose clamp and I ran out of gas with a quarter of a tank.

Pressure you check up front on the line to the cold start valve because it should be under pressure and it's easy to get too. Do not check it on the line coming off the FPR as that should not be under any pressure. For a pressure gauge you can just buy one for a 5 spot at a hardware store for water, attach a barbed hose fitting to it and be in business for under $10. The gauge doesn't know if it's measuring fuel or water. I wouldn't leave a water gauge hooked up permanently, but for short term use it's just fine.

That hose from the manifold to the charcoal canister needs to be sealed, I failed my first smog with it cracked - test failed as too lean with NOX, you'll have a manifold vacuum leak. I'd assume that hissing you hear is vacuum leaks or just normal releasing pressure from the tank (remove the gas cap and it should stop). Possibly displaying the intermittent idle behavior though?

Speaking of idle mine was inconsistent until I sprayed, WD40 I think it was, into the aux air valve and tapped it with a hammer from all angles. Normal behavior after that.

I have a slightly shaky/missing idle anyway and when replacing all the fuel lines and injectors picked up a good test - take the pipe off the AFM and poke the flap, 'priming' the fuel pump. When it's cold, do that, see if it starts immediately or not, it'll give you some more clues.

As a project I plan to install a 3-second timer for when I turn the key to 'on', to power the pump for 3 seconds as cars do these days, for an even easier start as instead of the pump running with the starter, it will already be running and up to pressure. Something like that might help you, but it won't fix the cause.

A part of posting is hoping the problem, answers for solutions is good for other members. Provided we think to scroll down the the list.

Over the years I have printed most applicable posts to have the answers filed in folders. Engine, Suspension, Electrical,... as additions to the BMW, Haynes repair instructions. Doing that was / is a good idea for stubborn, " Do it myself," eccentric types.

Thank you to members willing to teach from experience, adding to my files. This episode, the fuel pump coming apart occurred to me. It happens the fuel system in this '81 needs the same inspection, complete filter, pump, fuel line replacement as completed in my '79.

In the spring. Using the instructions posted for that adventure.