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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 5 Series > E39 (1997 - 2003)

E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 08-23-2014, 01:32 PM
nedmon nedmon is offline
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Mein Auto: 1998 528i, 1987 Carrera,
Hard Cold starting Fixed?

All,

The car has always started immediately but recently had been slow to start when cold. Hot start is fine, runs and idles fine, gas mileage fine. My pressure gage has an SAE Schrader fitting so I couldnt directly measure pressure but it did appear that a smaller squirt came from the Schrader when I released pressure with a screwdriver. There has been no gas smell.

So I went after the obvious, one injector was leaking from the nose so I replaced it.

I replaced the pressure regulator and no change, maybe a slight mileage improvement,

I inspected all the hoses and lines at the pump/filter and at the tank, all fine.

Yesterday I changed out the valve cover gasket to fix a smelly leak near the exhaust and guess what.

It started immediately this morning.

It looks like the problem is related to the affect on vacuum caused by the bad gasket so I released fuel pressure and left the filler cap off. Back to hard starting again. Next I released fuel pressure and with the filler cap back on it started immediately.

I had been planning to switch fuel pumps as I have a spare to see if the check valve might be the cause but will wait a while now after the possible/probable fix.

Any thoughts or explanation?

Ned
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  #2  
Old 08-23-2014, 02:01 PM
1hander 1hander is offline
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..as long as when you open it you dont hear pressure coming out of the crank case, if im not mistaken that woulfd mean your ccv is clogged/malfunctioning..

what your experiencing is normal...

so does it start ok now that you replaced the gaskets
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  #3  
Old 08-24-2014, 11:13 AM
1hander 1hander is offline
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my bad i thought you meant oil filler cap.... but still yes if you take the fuel filler cap off it will run crappy.. mine does the exact same thing..i wont even try to start it without the gas cap on.

any vacuum leak is going to affect starting because when theres a vac leak the fuel trims go all out of wack... plus the regulator works on vacuum as well, so lack of vacuum means the regulator isnt doing what its supposed to do either..
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Last edited by 1hander; 08-24-2014 at 11:24 AM.
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  #4  
Old 08-24-2014, 12:23 PM
nedmon nedmon is offline
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Mein Auto: 1998 528i, 1987 Carrera,
Clarification

I was able to repeat the hard start condition after replacing the valve cover gasket when i removed the oil filler cap and I assume that by doing that I replicated the bad vacuum condition caused by the leaky gasket.

When I put the cap back on the car started immediately when cold, even after I released gas pressure to simulate what I thought was a low fuel pressure condition caused by a leak somewhere.

The cold start problem has now gone away and what I am trying to figure out is exactly why.

Agreed the pressure regulator gets a vacuum signal but sort of doubt that the when cranking it would be much different from atmospheric.
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  #5  
Old 08-24-2014, 12:26 PM
1hander 1hander is offline
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ok so you were talking about the oil filler cap... then yessir ... sounds you got it naled down...congrats..

its exactly what your thinking.... removing the oil filler cap recreates the vacuum leak you had before replacing the seals... on some cars you can remove the oil filler cap without any worry of creating the vacuum leak(speed/density controlled engines) on our engines MAF (mass air flowcontrolled) we cant get away with it..because the intake starts to pull unmetered air through the vac lines via the open oil filler cap...which causes a lean run condition on all cylinders pretty much, then the ecm starts adjusting fuel trims to stop the misfire...then because the vac leak is to big for the fuel trims to overcome, they get maxed out then she gets angry and
starts talking to you in 4 letter words ... in the form of 4 digits ... 0304 1958 1634 1479 5421 0021 0124 0218 8310 8176 2135 2107 8134 4653 5498 7532 1867 9269 4269 7981 3513 8768


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Last edited by 1hander; 08-24-2014 at 12:37 PM.
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  #6  
Old 08-24-2014, 03:22 PM
nedmon nedmon is offline
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Looking back at my problem diagnosis, I believed that I was losing fuel header pressure and that was causing the hard starting when cold, HOWEVER, I switched it on without starting a few times and this did not improve the cold starting meaning that it was NOT a pressure issue.

Thank you both for the wise words

Ned
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  #7  
Old 09-21-2014, 11:33 AM
nedmon nedmon is offline
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The illusion of success it was.

The hard starting, that is, it usually fires the second time I crank it, continues. Perhaps a better problem definition is that it does not start the first time I spin it after it has sat overnight. I"m not sure that cold starting is the issue as it will start immediately after it has run for a few seconds, not long enough to change the temperature in the dual temperature sensor.

I just installed the original fuel pump in place of the new one I put in last Fall thinking that the check valve might be leaking the fuel but no. The starting behaviour has not changed.

There is no smell of gas and all the injectors are tight,

Any and all thoughts are welcome.

Ned
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  #8  
Old 09-21-2014, 01:52 PM
pshovest pshovest is offline
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Does your check engine light work? Is it on?
Pull the fuel pump relay, install a jumper to force pump to run, try to start with jumper in place.
Stuck ICV may not let enough air into a cold engine. Does a little throttle improve starting?
Vacuum leaks cause intake air to bypass MAF resulting in low or no fuel being injected. Remove all boots between MAF and throttle valve and inspect for cracks. Inspect all CVV hoses. In particular the hose that drains to dipstick tube. This hose often breaks or disintegrates from oil contact.
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  #9  
Old 09-21-2014, 08:02 PM
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16valex 16valex is online now
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Have you replaced your fuel pressure regulator? I would if not already.
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  #10  
Old 09-22-2014, 09:05 AM
nedmon nedmon is offline
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Thanks for the responses.
No CEL
Runs/idles smoothly, good gas mileage.
I cleaned the ICV, rattles nicely now.
There are no cracks in the corrugated rubber/plastic inlet hose.
I treated the car to a new pressure regulator last Spring, no change.
Tomorrow I will pull the CCC and inspect it.
My brother from Ireland says who cares if it takes 2 tries to start when cold. His phrase was " move on"

Ned
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  #11  
Old 12-18-2014, 05:53 AM
nedmon nedmon is offline
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I took my brother's advice to forget about it and, for a few months, moved on. Benign neglect is one of my favorite therapies.

Yesterday however, I had better ears than mine check and discovered that the fuel pump does not run when the key is switched to position 2. Normally the pump runs for 2 seconds when the key is switched on to get fuel pressure up before cranking the engine.

So, since the fuel pump runs when the engine is cranking but not before, I believe that this is the cause of my hard cold starting problem. I will check wiring, fuel pump relay and DME connection to the relay next to determing what exactly is wrong.
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