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7 Series - E65 / E66 (2002 - 2008)
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Old 12-20-2014, 09:28 AM
fishrmanblu fishrmanblu is offline
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Location: Ireland
Join Date: Dec 2014
Posts: 1
Mein Auto: 735i
2003 735i trouble starting

2003 735i (135k miles) has become increasingly hard to start from cold. First started giving trouble about September as the Irish summer ended. If left overnight it was hard to start in the morning, but ok for the rest of the day. But now if I get it started it will be grand turned off for up to 3 hours but any longer it'll give trouble.

Normally what happens is I push the start button and it tries (with plenty of swing power) to start.. 70% of time it starts after 20 seconds or so, the rest of the time it will time out (maybe after 25secs). If I repress the start button it will flood, so I wait 3 or 4 minutes and repress the start button and 90% of time it will start (but increasingly not start here too). If after the two failed attempts to start I go back to the car hours later it will start within 1 second. (lately this is the only circumstance where the car will start straight away as normal).

Took it to mechanic1 who said it was the alternator (battery is less than year old but if I sit listening to radio the recharge warning will come one within a minute or so. (most of my driving is cold start 10minute journeys).

Took it to mechanic2 who said spark plugs were fine, cleaned coil packs as they looked a little green at connection. Diagnostics showing misfire on two cylinder and secondary air fault. These faults were there since before I've owned car but never got to the bottom of them, but it was running normally so didn't bother me too much. Mechanic2 said alternator and battery were fine, and couldn't fine any dodgy connections etc.. everything looks fine. I think he said there was a crank position sensor fault on the diagnostics but didn't know if it was genuine as the not starting may be throwing up spurious faults.

Took it to mechaic3 (german car specialist). He said there were lots of global alarms that he cleared, a bit vague. He did an oil flush but this made no difference. He said there was no compression when trying to start so he recommended a compression check (500+ cuid) but I took it back to mechanic2 and he did it for 120 (not sure why such a price difference). Anyway cylinder compression test passed..

Problem remains.. I could always get it started on the second attempt, but that's becoming harder..

I'm not 100% sure on this but it seems to be harder to start in damp wet weather. It didn't surprise me that it started fine for mechanic2 in the morning as it was indoors overnight.. and I've a feeling it'll be fine come summer (if I don't drive it over a cliff in the meantime!)

Any thoughts as to what could be the problem.. next step?
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Old 12-21-2014, 06:16 AM
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mybmw408 mybmw408 is offline
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Location: San Jose
Join Date: Oct 2013
Posts: 558
Mein Auto: BMW 750i
I have been getting the same issue with my 2007 750i. I have new plugs ran diagnostic showed a few misfires, cleared codes. Happened to me again the other day. I haven't had any issues like this till it started raining. It cranks strong, after a 20 seconds or so it turns on and I smell gasoline. I bought a new fuel filter and a few coils, haven't installed them yet. Hope someone could shed some light before I change unneeded things.
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