Difficulty on cold start

[yohannes]

Hi again everyone, The UDM journey is indeed one that is fraught with endless tribulations. Haha. I finally fixed my red glowing 'check engine oil pressure' problem which turned out to just be a bad oil pressure switch. A great relief for me after spending more than 15k in 5 months of ownership and still having issues crop up on the car. Was glad that it wasn't another big problem. Anyway, the latest issue that I am facing is that during cold starts ( most evidently in the mornings ) or after leaving the car parked for hours at the end of my work day, it is difficult to start. The car cranks with no issues but when the engine starts up, it seems to bog down and a few taps on the accelerator will solve the problem. That is during the better days.. On days when the car is in a bad mood, the engine dies off within seconds after starting up and coughing a bit. After this happens, it takes about 5 - 6 long cranks before the car finally starts. When cold, it feels sluggish and reluctant. However, after 15 minutes of driving and when the car warms up, it seems to be fine. The workshop that replaced my oil pressure switch diagnosed that I am having low compression in cylinders 2 and 3 , and they suggested that I return to check with the workshop that recently performed a top overhaul + replaced my entire engine head , oil pump and crankshaft sensor . Visited the workshop on Saturday and the owner was confident that the problem was not with the engine. A diagnosis revealed misfiring on cylinders 2 and 3. Was asked to leave my car at his place for an in depth diagnosis. Will however need to wait till I can do without the car for a few days and I also have my concerns on leaving my car again. At the same time, I have been doing some research on various forums and it seems that this could be a 'fuel supply' problem which could narrow down to a fuel pump relay or fuel line regulator. Wonder if any one has had experience with the same problem. At the same time, if it was a fuel pump relay or fuel line regulator, would it cause misfiring on cylinders 2 & 3? My car is a 2003 E46 318i 2.0 CKD . Engine is the N42B20. Thanks for all the replies!

 

[Ibrahim Hanif]

Have you changed the ignition coil?.

 

[jarance]

Sound like a faulty check valve of the fuel pump.
Unfortunately, the check valve is not serviceable and hence need to change the fuel pump.

 

[yohannes]

When my mech checked my car in Feb, he says that all 4 ignition coils are very new, probably replaced not too long ago by the previous owner. My spark plugs are newly replaced as well.

Will take note of that. Is there a possibility that a faulty fuel pump check valve causes misfiring in only two of four cylinders ?

 

[jarance]

When my mech checked my car in Feb, he says that all 4 ignition coils are very new, probably replaced not too long ago by the previous owner. My spark plugs are newly replaced as well.

Will take note of that. Is there a possibility that a faulty fuel pump check valve causes misfiring in only two of four cylinders ?

When the check valve is faulty, the fuel that is suppose to stay pressurized in the fuel rail leak back through the faulty check valve when the pump is stopped. When this happen, there is not enough fuel to feed the fuel injector during the first cranking. Starvation of fuel may caused misfiring in your case.
Your problem seem to be OK when when the car is warm up. This is due to the fuel pump being force feeding the fuel rail and keeping it pressurized.

try this test. Turn on your ignition but don not crank the engine. wait for about 1 minute and then crank the engine.
this test is to allow the fuel pump to built up the pressure in the fuel rail and purge the fuel line of air via the fuel regulator return line.

 

[yohannes]

Nice technical explanation there. Appreciate your advice, will try that this evening...

 

[yohannes]

Left the car in my office car park for about 4 hours since morning. At lunch time tried turning the ignition without cranking the engine and leaving it for 1 minute before cranking. Didn't help and it was still difficult to start. Had to crank quite a number of times and for quite long each time. At the final try, I cranked the engine and fully depressed the accelerator the moment the engine was coming to life and managed to start it.

After successful starting and driving some distance, tried shutting off the engine and starting again and it was good as new . Did this a few times along the way to lunch and did not have any problems as well. After leaving it for 1 hour over lunch, the engine started with a little of 'bob bob bob' sound and was fine within seconds.

Conclusion is that whenever I leave the car for a longer period, the problem surfaces. In the event that it is a problem with the fuel delivery, why is it that only 2 cycinders specifically 2 & 3 are misfiring?

 

[Alex5522]

Try to read this forum bro : http://forum.e46fanatics.com/showthread.php?t=897616&highlight=problem+on+cold+start
Hopes it will help.