E39 cold start problem - resolved with a restart?

8886 Views 66 Replies 10 Participants Last post by borntodeal, 3 mo ago

wc123wc

Discussion Starter · Sep 13, 2018

Hello,

I have a 2003 530i that has a hard time when it's cold outside. Yesterday the temperature was about 16C (in Toronto), so it was below 20C for the first time in few months and the car started but there was no power. Eventually when I had stopped at a stop sign the car gave me errors and was about to shut down so I turned it off. Right away I started it and it started just find. No codes, no loss of power...nothing wrong, perfectly fine!

This is not the first time it has happened. I had cold start problems with it last winter, but the problem was always resolved by restarting the engine.

My question is this: what can cause cold start problems that can be resolved with a restart?

^The reason I am phrasing the question like this because there are a lot of things that can cause a cold start problem but don't get resolved with a restart. I am trying to narrow down the list by knowing that an immediate restart always resolved the problem!

Thank you in advance for your help!

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borntodeal

· #61 · 4 mo ago

When time permits, I'll replace the fuel pump relay and report back.

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Chedley

· #62 · 4 mo ago

Try to check or replace the starter relay instead. As mattmar1 points out, if there is fuel pressure at the rails, then the fuel pump relay is probably ok.
I'd suspect the ignition switch, or the starter relay.

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borntodeal

· #63 · 3 mo ago

Chedley said:
Try to check or replace the starter relay instead. As mattmar1 points out, if there is fuel pressure at the rails, then the fuel pump relay is probably ok.
I'd suspect the ignition switch, or the starter relay.

Thank you for your kind advice. The car cranks strong but will not start at 45 degrees F, so would that still be (possibly) the ignition switch or the starter relay?

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mattmar1

· #64 · 3 mo ago

if i understand correctly, the car will crank at 45 or under but not start. both the switch and relay would be pretty much eliminated if this is the case. not seeing anything as of yet that has been suggested so far in this thread thats been checked, we are doing the best we can from a distance. whats the fuel pressure whne cranking? do you have BOTH fuel pressure and spark when it wont start?

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borntodeal

· #65 · 3 mo ago

mattmar1 said:
if i understand correctly, the car will crank at 45 or under but not start. both the switch and relay would be pretty much eliminated if this is the case. not seeing anything as of yet that has been suggested so far in this thread thats been checked, we are doing the best we can from a distance. whats the fuel pressure whne cranking? do you have BOTH fuel pressure and spark when it wont start?

Thank you for your kind responses. In theory checking these things is plausible, however, in reality, it would mean so many things must occur at once, I would need to drop off the car, in advance of a cold day and hope for a really cold day and have the mechanic check this. I do not have the ability to quickly check fuel pressure on my own. I am confident spark is good, unless the coils could be temperature sensitive? They are aftermarket. Thoughts on that?

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mattmar1

· #66 · 3 mo ago

brand of coils? doubt the whole set is bad though. doubtful. so, this thread is going nowhere, its becoming an accumulation of unanswered questions. on the 2002 Y/M, there is a port on the fuel rail, schrader valve. one can be gotten at HF around $30, for reading fuel pressure.

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borntodeal

· #67 · 3 mo ago

mattmar1 said:
brand of coils? doubt the whole set is bad though. doubtful. so, this thread is going nowhere, its becoming an accumulation of unanswered questions. on the 2002 Y/M, there is a port on the fuel rail, schrader valve. one can be gotten at HF around $30, for reading fuel pressure.

I hear you. Terribly sorry. I will check into the $30 pressure reader and give that a try on the non-starting day. Indeed it is going nowhere. In order to test the issue, I have to be stranded, unable to start my vehicle on a 45 degree F day (this is at 4am when I am heading to a job as I am a professional actor) and at that time it is hard to test. I have no thoughts on how else to set up a 45 degree F day other than those days and in that moment, I will be needing to order an Uber. Any other thoughts on how to test this are welcome, otherwise, indeed this is a thread going nowhere. Apologies.

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