The never, ever, ever ending cold RE-start problem... again

E28 technical advice asked and given! Troubleshooting, modifications and more.
oldblackcar
Posts: 233
Joined: Nov 11, 2009 11:03 AM

The never, ever, ever ending cold RE-start problem... again

Post by oldblackcar »

This isn't your typical cold start issue. It's a cold RE-start issue.
The car starts fine - cold - other than having a little bit of a long crank time. If you start it and drive it to normal operating temperature it stops and restarts without an issue.

The problem is this:
If I start the car and drive to the store 2 minutes away and shut it off - upon getting back in the car won't restart. It just cranks and cranks - very freely - as if there is no compression. It will do this sometimes for 5, 10, 15 and 20 minutes. During the cold season it happens - but isn't as drastic and is less frequent.

Now that it's hot out - it happens every time without fail and has only gotten worse. I run out for a coffee and I'm stranded for 20 minutes burning up my starter.

If I start the car and drive it for some distance, the behavior won't show up and doesn't for the entire day. It's only after an overnight cool down. Otherwise the car idles fine and pulls really well - it's a thrill to drive.

The car has new:
Injectors (problem was identical with old injectors)
Coil, cables, plugs, cap, rotor (problem was identical before all this)
ECU (Problem was identical with old ECU)
New in-tank and external pumps (no change)
New CTS (no change)
New FRP (no change)
CSV and TTS have been removed

The only thing that hasn't been replaced is the AFM.

and... If you've read this far. Yesterday I started up, went right to the car wash and got it line. The car idled fine, but after waiting in line for a few minutes the car would almost cut off when I pressed the accelerator. I'd depress the pedal quickly and the car would damn near conk out. If i slowly worked the accelerator it would cough back up to speed. On a hunch I jumped out and pulled the plug on the 02 sensor and the sputtering on pedal depression stopped - but by that time the car had been idling for a while and was already up to temp. So I don't know..
Last edited by oldblackcar on May 13, 2011 7:46 AM, edited 2 times in total.
Blue Shadow
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Location: SE PA

Post by Blue Shadow »

Instead of driving out for coffee and burning up the starter for 20 minutes when you return to your car, drive your car for 20 minutes before you stop for coffee then you'll be all warmed up and ready to restart.
oldblackcar
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Post by oldblackcar »

Thank you for such in-depth insight. I like coffee, but not that much.
peeeot
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Joined: Aug 01, 2009 10:23 AM

Post by peeeot »

Why'd you remove your cold start valve? Also, what's TTS?

Perhaps on the initial cold start, when the 02 isn't warm enough to be considered by the ECU and and CTS is indicating fully cold engine, the ECU starts with a mixture just rich enough to get the car up and running (with some effort, thus the long crank time). Then, after your short drive, there is enough heat in the engine for the ECU to start leaning the mixture on the pre-programmed "assumption" that there is still a CSV. Since there isn't a CSV, though, the mixture is now too lean to start the engine, so you crank and crank but no go until it cools enough that the ECU enriches the mixture again.

Have you tried clamping off the fuel return hose while cranking when it's having the problem? That would force a richer mixture; if it starts up then you'd know that's what's going on.
oldblackcar
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Joined: Nov 11, 2009 11:03 AM

Post by oldblackcar »

TTS - Thermo Time Switch

I pulled off the CSV after reading various recommendations on the board as to it's potential for leaking. This behavior was there long before I did that. I'd have to agree that your theory makes sense - but this car is supposed to run without the CSV. Particularly in 70- 90F degree weather.

I also agree that it is a fuel/air mix issue. I just don't know what the magic bullet is.
peeeot
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Joined: Aug 01, 2009 10:23 AM

Post by peeeot »

You could still try clamping off the return line. Have you confirmed that you have spark? A timing light would be handy for checking that.
oldblackcar
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Post by oldblackcar »

Spark?
Mr.ProjectCar535
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Location: San Jose, CA

Post by Mr.ProjectCar535 »

oldblackcar wrote:Spark?
Make sure your spark plugs are getting power and providing the spark needed to combust the air/fuel mixture.
oldblackcar
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Joined: Nov 11, 2009 11:03 AM

Post by oldblackcar »

The car starts just fine. Since I unplugged the 02 yesterday it's actually starting better than the day before...
As for the RE-Start issue - I have no reason to believe that is any different.
peeeot
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Joined: Aug 01, 2009 10:23 AM

Post by peeeot »

All the same, it is easy to check, and worth the time. Weird things happen with cars sometimes. If it's sparking but not starting (on the RE-start, of course) then you've definitely ruled out the ignition side. Unless your computer is incorrectly advancing the spark for some reason. Which is unlikely.
oldblackcar
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Post by oldblackcar »

I thought I had it licked with the new ECU but the problem was the same. I have a new AFM coming. I'll see how things go when I put that in.
oldblackcar
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Post by oldblackcar »

The new AFM is in the car and I've applied a slight TPS adjustment - so far the car pulls much better, doesn't bog or bumble around upon quick pedal depression and some of the rough spots that used to be felt in WOT were not there today when I took it out for a spin up to and at full operating temperature.

I'll test tomorrow to see if I can run it for a few minutes, shut it off and then restart it. That will certainly be the test.
shagrath
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Post by shagrath »

oldblackcar wrote:The new AFM is in the car and I've applied a slight TPS adjustment - so far the car pulls much better, doesn't bog or bumble around upon quick pedal depression and some of the rough spots that used to be felt in WOT were not there today when I took it out for a spin up to and at full operating temperature.

I'll test tomorrow to see if I can run it for a few minutes, shut it off and then restart it. That will certainly be the test.
A failing AFM can cause your issue for sure.
oldblackcar
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Joined: Nov 11, 2009 11:03 AM

Post by oldblackcar »

Test Drive #1:
It's cold and rainy out now. I started the car (typical long start for one that has no cold start system). I drove it around the block and parked it. Waited a few minutes as usual - went back and it started right away, which is something it hasn't done in a long time.

I'm going to try again tomorrow and I'll report back. If it works again - I'm going to call it solved and say that the AFM was not only the problem all along - but the source of many, many other headaches and I wish I had started with it before replacing all the other components.

Although I'm not at all upset that everything on the motor has been replaced in the last 20,000 other than the ICV.
coopa.s
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Location: Sydney, Australia

Post by coopa.s »

What you are describing (I think you already know this) is that your engine is flooding. This happens to the M50/2/4 generation of engine all the time over here, as people just drive them to the shops and back. The car doesn't get a chance to warm up and is always on warm up program- thus eventually they flood. Then they call servicemobile and get angry that I just started it in 5 minutes.

Have you checked the fuel pressure reg? Or swapped it with a known working one?

Put your CSV back in and see what happens.

Next time it happens, keep cranking it with your foot to the floor. It will start eventually :)
oldblackcar
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Post by oldblackcar »

I've swapped out the FPR - the whole fuel system is new all the way to the injectors.

I just tested it again.
Drove it around the block - let it sit for a few minutes - put the key in and vrooommm!

I'm going to call it solved.
oldblackcar
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Joined: Nov 11, 2009 11:03 AM

Post by oldblackcar »

So - a week after thinking it was over - it's back...
Yesterday the same thing happened again. This time it started within a few minutes - but it still happened, just as before.

There is no end to the aggravation.
shagrath
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Post by shagrath »

The only thing I can think it might be would be the 02 sensor. However... I wonder if maybe the spd/reference sensors are acting up... Also, what if this isn't temperature related? What if you have an intermittent connection issue that when tampered with seems to go away? Oddly enough spd/reference sensor wiring has a weird way of doing that, from my experience.

02
spd sensor
reference sensor
oldblackcar
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Post by oldblackcar »

The only thing that makes me want to scream about the speed and reference sensors is that I am ALWAYS replacing them. I guess it's worth a check - but I put new ones on at least once every year or two. It's like a constant game of cat an mouse with this thing...

It's like my old German Sheppard - she'd get an eye infection and we'd put cream on her eye - so it would move to her ears. We'd put cream there and it would move to her lips. We'd put cream there and it would move to her ass. We'd put cream there (which is fun with a 100 lb German Sheppard let me tell you) and the infection would move back to the eye.

After a while I just get sick of chasing bullshit around and around with these Bavarian money pits we love so much.
Son of a
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Post by Son of a »

I see lots of mentioning of part replacement, but not much of part testing. A DVOM and the Bentley (not to mention this site) are the resources you need to check the applicable values for just about every electrically controlled components in an e28. As these cars get older, the odds that a NIB replacement part is bad out-of-the-box only goes up. I would test everything you have replaced and not take for granted that any of those are good, just because they are new.

Remaining issues could be as simple as the connector on the back of the ecu., or the socket for the main or fuel-pump relay, or even a case of bad engine grounds. e28s do not like voltage drops, bad grounds or even slightly loose connections.
shagrath
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Post by shagrath »

Son of a wrote:I see lots of mentioning of part replacement, but not much of part testing. A DVOM and the Bentley (not to mention this site) are the resources you need to check the applicable values for just about every electrically controlled components in an e28. As these cars get older, the odds that a NIB replacement part is bad out-of-the-box only goes up. I would test everything you have replaced and not take for granted that any of those are good, just because they are new.

Remaining issues could be as simple as the connector on the back of the ecu., or the socket for the main or fuel-pump relay, or even a case of bad engine grounds. e28s do not like voltage drops, bad grounds or even slightly loose connections.
QFT! My buddy has been chasing his tail on his 325e for almost a year now because he refuses or does not how to check components.
oldblackcar
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Post by oldblackcar »

You make a very valid point about testing. I guess it is a patience thing with me. The most frustrating part is that nothing I have replaced has changed the behavior - tested or not.

The car starts and runs better then it ever has and will as long as you don't shut it off before it is fully up to operating temp. If you do - you're going to sit for a while.

If you shut it off when warm - the problem never appears.
spinedocab
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Post by spinedocab »

Look, you've got to check a few things WHILE THE PROBLEM IS OCCURRING.

Is there spark at that time? If so, is there fuel at that time. If so, is there too much fuel (over pressure) at that time...etc...etc.
TSMacNeil
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Post by TSMacNeil »

From my post on the Bosch Motronic...

(peeot was on the right track...but you don't need the CSV)

Fuel injection

During start-up from cold, injector pulse duration is increased to provide a richer air/fuel mixture and pulse frequency is also increased. In addition, the ignition timing is also retarded. Injector frequency & pulse duration and degree of timing retard depend upon the engine temperature both during start-up and immediately afterwards. If the engine is restarted within one minute of the first start occurance, less overall fuel is injected to reduce the risk of fuel flooding into the engine.

So, a few thoughts:
(1) you have never mentioned the IASV (ICV) does it vibrate on ignition on? Have you ever cleaned it?

(2) Since the ECU enrichens the first cold start, then leans a subsequent start (as described above) I'd check to make sure you have good clean injectors with plenty of fuel pressure at the rail to begin with. If your pressure is down, and the ECU leans from that...you may be too lean on your subsequent start attempts.

I dunno, you've thrown a lot of parts at it, but you're gonna have to start breaking this down logically. Where does the ECU get the engine temperature data? The CTS. (you may need to test it this time, maybe its DOA out of the box...is it blue?) How's the connector for it? The wiring? The sensor might be good, but no signal getting to the ECU above your glovebox... I haven't seen any fuel pressure numbers...how do you know what you have at the rail?
Roll your sleeves up, start testing some stuff.

Also, consider the common denominators here, this problem only occurs on a "cold restart"...so, the ECU is leaning out this restart-and you are still likely in open-loop with the 02 sensor...it uses a fixed map until the 02 is up to temperature and signalling correctly.
oldblackcar
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Post by oldblackcar »

spinedocab wrote:Look, you've got to check a few things WHILE THE PROBLEM IS OCCURRING.
If it were to happen at a place of my bidding that would be great. Problem is it's usually a parking lot at the doctors office or outside a grocery store.

It's certainly not a planned event and running diagnostics outside the local Latin market with a car full of chicken that needs to be refrigerated isn't quite what I had in mind. While it would be great to do - it's a bit impractical. I've tried to duplicate the behavior in my driveway to no avail.

I do like the over pressure idea though.
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