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Discussion Starter #1
Hey everyone, I have a new problem with my car that I can't explain. I've done a fair amount of troubleshooting. I really need some advice because my car inspection is in a couple days and I apparently can't trust it to start when it's warm.

1) I've checked the error codes with a carsoft adapter.

1)A) There was an EWS error in german saying "key 1 not recognized" and I wasn't able to duplicate that with any of my three keys. I don't know which key is "key 1"

1)B) There was possibly an error for prefeed pressure to be too low. The problem is, the software didn't actually go out and tell me what that error was. I got DME/DDE error 4704, 256 and 4693 errors. None of which I could find information on. I don't know when these errors were logged. Maybe someone can point me in the right direction as to what these errors are. I found only one reference to 4704 being low pressure.

2) I checked the pressures and everything I could find on live data with the carsoft cable.

2)A) the prefeed pressure was between 3.6 and 3.8 bar depending on if it was full throttle at 3500 rpm or idle. Not much difference and the difference of 0.2 bar won't prevent it from starting. I found that by unplugging that pressure sensor (on the fuel filter) the computer reads 4.4 bar. Interesting that open circuit reads the maximum value it can read. So, I figured if I leave it unplugged it will always TRY to start even if it doesn't have sufficient fuel. The high pressure pump will pull a vacuum and then stall if there is something plugged or the electric fuel pump(s) aren't running. When it wasn't starting, the prefeed pressure was just fine with the key "on" and not running.

2)B) The high pressure rail was perfect. The requested versus actual pressure was within a couple percent even under transient conditions (sudden acceleration changes). It went up to 1380 bar and idle was something like 300 or something. All of the other live data values seemed normal.

3) I checked the fuel pump relays. I found there were 3 of the identical relays, so after popping open the covers I could see that they were all looking good. I swapped them all around in case there was a bad one somehow. No difference.

4) The battery is new. It is a very powerful Exide AGM battery and the charging system is good.

So, what it does is that it will just crank and not fire. It usually starts when it's cold but if I try to start it again later when it's warm, it might not. Several times, it cranked then instantly ran for 1-2 seconds then instantly stalled again with no stumbling or anything. It was as if I turned the key off.

I tried to verify if the cam position sensor works or not. Today, I tried unplugging it and it very strangely, it fired for several revolutions and then died again even without it plugged in. That doesn't make sense to me because it didn't do that even when plugged in. I ordered a new one to see if that will make any difference but I don't want to buy too many parts without knowing if they are bad or not.

The car has never stalled while running. I think that is an important point to make. Once it's running, it's not a problem.

Also, when I had the carsoft cable plugged in, I synchronized the EWS to the ECU computers thinking it might be a security/immobilizer problem but it made no difference.

Any help would be greatly appreciated! I have no idea what to check next or what to do. I've spent hours testing different theories and trying different things and I have no idea what the problem is.
 

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Discussion Starter #2
Well I got a new cam sensor and it does the exact same thing. Actually, I drove it to the DHL pickup point and put it in at the parking lot. It started when I wanted to go home so I drove it back to my apartment and it wouldn't start in my parking place. I am at a complete loss of what could be wrong now.

Is there anyone out there who has an idea?
 

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Sounds to me like an immobilizer problem. You mentioned that you weren't able to replicate this problem on any of your three keys. I'm assuming you have two master keys and a valet key. It might be either one of your keys or your the immobilizer unit.

Keep all keys with you and if the problem arises again, try different keys.
 

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Discussion Starter #4
Thanks for the reply! Will the valet key key be different in some way? I assume it has a chip in there as well. Next time I'll try my other keys. And maybe I'll try taking the chip out of the key to see what the car does (i.e. if it cranks at all).

I actually went to the dealer to ask about the possibility of an immobilizer problem. He said that if it cranks, it's not likely to be that. The car clearly has a starter interrupt circuit for when it's in gear for example, so I'd think that if the immobilizer is intelligently designed it would also cut the starter in addition to the injectors.
 

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That's interesting. I've worked on Japanese and Korean cars for the majority of the time and if the immobilizer doesn't recognize a key, it will not fire the injectors but will still allow the car to crank. I didn't know that BMWs also interrupt the starter circuit along with the fuel injection circuit.
 

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Discussion Starter #6
That is interesting. Let me know what you think about this idea then: take the RFID chip out of one key. When I replaced the rubber buttons I saw it's basically just sitting in a little cavity. When you open it up, there is nothing holding it in place anymore so it would be easy to get it out (and it's not that I've messed with the keys, I did this some months ago and the chips are exactly where they used to be).

With one key that's still intact, see if it starts. If it does start, see what happens with no chip. If it doesn't even crank, then it tells me the immobilizer works and it's probably not that. If it DOES crank still and doesn't start with no chip, then it tells me that there is at least a possibility of it being the immobilizer.

The puzzling thing is that it always starts when it's cold. I wouldn't think the EWS immobilizer thing would be getting very warm but then again, I don't know exactly where it is how how much power it consumes. I suppose it's reasonable to believe that if it has a cold solder joint the car would continue to drive fine until you have to start it again.
 

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That is a good idea. Anyway to use the process of elimination to narrow down a potentially failed component is progress.

It is very weird though that it starts up no problem when cold. Makes you wonder.
 

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Discussion Starter #8
Ok, so I just went out to try something different. I need to do the leakdown test yet on the injectors, but today is a holiday in Sweden right now so everything is closed anyways. I should be able to find some bottles and tubing from my lab though. Doesn't look too hard to make a simple setup if I don't have time to order something. Just plug the return line to the system and put the tubing from the injectors into some containers.

So I went out thinking there must be many things that could tell the computer to not activate the injectors. On a gas engine, putting the accelerator to the floor cuts the injectors. That dates back to the days if you had a flooded carbureted engine. Well, putting it to the floor it roars to life. Putting it to the floor where you feel a "click" and the kickdown switch is engaged it won't start. I'm taking stuff apart above the pedals to see where the kickdown switch is. Maybe it's getting stuck. Maybe something is physically broken in the accelerator position sensor.

It's cold out right now, 5 degrees C and cloudy. I had the engine running all but 5 minutes and it quit being able to start even though the engine water temp was only about 25-30C . I suppose, though unlikely it could be this stupid kickdown switch? If I find it, I'll just unplug it to see what happens. I don't think it really needs it.

Also, if I took the chip out of the key, it would turn the fuel pumps on but NOT crank. So that tells me the keys ARE being read ok! That's a good thing. The EWS unit (or whatever it's called) is very expensive because it needs to be coded for the car from BMW. I put the chip near the ring and it cranks. So at least that works :/

So, new unlikely lead and I ruled out the immobilizer? I guess that's a start.
 

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Discussion Starter #9
Bah. I went out to investigate that kickdown switch thing. It doesn't have one. It uses the TPS and the click is apparently a typical BMW thing where it just takes a bit more resistance to click and push it that much further. Upon more tries, I found it was just random chance if it would start or not, pedal on the floor or not. So that wasn't a valid clue. Just randomness. I guess I'll try going to the dealer or a diesel specialist tomorrow.

And I found this leak back kit:
http://www.ebay.co.uk/itm/VS2048-SE...160?pt=LH_DefaultDomain_3&hash=item2324b949b0
I guess that might be what I need?

I found out it starts without the MAP sensor plugged in. Doesn't throw a dash light. If unplugged, the CR pressure sensor prevents it from starting which is understandable.

One thing I noticed is this: If I drive it to get it warmed up, then start it, stop it start it many times, it takes longer to crank until it won't start at all. If it runs continuously once it's started and has no power issues, what could be going on here? Other times it won't fire up at all.

Oh and I wish I included this initially, my car does this most of the time when it doesn't start. Most of the time it doesn't try to fire at all.
http://www.youtube.com/watch?v=1tMpyDMPWEc
 

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Discussion Starter #10
I ordered a new Bosch prefeed pump and it took over a week to get to me. I just installed it and to my dismay, it still has some problem somewhere. The new pump is much noisier than the old pierburg pump but I'll just assume that it works. I'm a bit annoyed about the noise. I really hate Bosch...

So what it does now is this: If you try to start it after getting it warm, it will probably start. If you turn it off after just a few seconds of idling and immediately try to start it again, it will take longer and longer to start and the 3rd or 4th try it won't start at all. It just cranks.
 

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Sorry to resurrect such an old post, but did you ever resolve this.

My E39 530d Touring is doing the same thing, it starts then very quickly cuts out (1/4 of a second to 1 second later)...

The throttle position makes no change it at all.

MAF lead makes not change

Crack sensor lead removal stops it from firing up at all, so seems OK.

It's got fuel, oil, ATF Fluid & coolent.

The fuel rail pressure sensor was replaced a couple of years ago as it had cracked & was squirting diesel around the engine bay (so I am assuming such a young sensor should be fine & when it did fail it would let it idle).

my generic ODB reader didn't find any faults
 

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Discussion Starter #12
Actually, all this time later it has always started perfectly since I last posted, whether it's -30C or +30C outside. I think it has to have been the prefeed pump. The one under the front door on the left side. I assume UK cars still have it on the left side.

I suppose it's possible that if your other components are in better condition than mine, it might be able to start momentarily and then stall due to the lack of prefeed pressure?

Thinking back a couple years ago, I can't remember why I thought the prefeed pump wasn't it. After I replaced it, I think it always started. Maybe it didn't start once because of air... no idea.

There are ways of reading all the pressures with bmw software acquired by other means... but I'm not the guy to talk to about that :) I got it working once a couple years ago and that was it. With that you can read rail pressure and prefeed pressure. If the rail pressure isn't 250 bar or above while cranking, the injectors won't open. If the prefeed pressure is below 3 bar (should be 4 bar perhaps???) it may not have enough for the high pressure pump to get the 250 bar.

If it starts then stalls, it must not be a leaky injector. From what I understand (and I could be wrong of course...), one leaky injector and it will likely still start. It just squirts a bit more fuel back into the return line. No harm. Two leaky injectors and the hp pump may not be able to provide the 250 bar required to open the injectors to start. The available pressure will be higher once the engine fires for a few revolutions, so it doesn't sound like that's your problem.

Hope that helps. Sounds like it's your prefeed pump. iirc, it's something like 100-150 GBP. Don't bother with cheap knockoffs. I've heard they don't provide the pressure required. That and they are noisy as hell. Get either Bosch or Pierburg, but Pierburg will be expensive (that's the OE part). If you can do it yourself, it's cheaper than having the dealer diagnose it. It's not a bad job. If you have a lot of miles, they go bad anyways so even if it's not bad, it's just saving time in the future for you.
 
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