2008 318i (Auto, 145K) cranks up but won’t start

So about a month ago, I drove to my 318i (2008 Auto) to the shop as usual. It’s never given me any issues or shown any signs of. I’ve only had it for 3months as 2nd hand though (145K). When I got back in the car after less than 10mins in the shop, the car wouldn’t start! Cranked up but no start. So I phoned my breakdown cover. Whilst I was waiting for the recovery, I decided to do a bit of investigation and came across a post where someone mentioned the fuel pump fuse. Struggled to work out which fuse number it was since the fuse diagram that came with the car wasn’t very help. Just when the recovery was about 10mins away, I managed to work out it was F70. I took the fuse out, wiped it between my fingers, slotted it back in, attempted to start the car and it started! thought I had it all figured out but how wrong I was! Told the recovery guy all was well now so he could go. I drove about 2miles to my mate’s garage, parked up to go and look for a new 20A fuse to replace the F70. But before replacing I decided to try starting again and it wouldn’t start. After replacing it worked fine for nearly 3wks without any issues.

Then the issue returned when I went to see a mate. I parked up, finished with the mate and got back in the car all in less than 30mins and the car wouldn’t start! Tried swapping F70 with other fuse and no luck this time so ended up getting towed to the garage. We run the diagnostic and it came up initially with a catalogue of codes: 2ACB; 30BB; 2E85; 9CCE; A8C2; 9CDB; 2A9A; 2ACC; 2DED; D373; 5DF7; 5E19; 5DE2; AOB4; 9CB5; 9CC8; 9CC5; A8B6; A559; C90B.

Then a friend advised me check the battery, alternator and earth strap. I couldn’t test the battery and alternator but decided to override the earth strap by joining a cable from the chassis to the engine, tried starting and guess what?? It started! so I thought bingo! finally found the problem! To be honest the strap looked knackered and badly corroded. So I changed the strap and everything was working fine and drove home with no issues, even going to the shop on the way.

Got in the car the next day to go and pick up my son for school and it started fine. I got to my son’s house about 3miles away, parked up, strapped him in and tried to start and it won’t start! Rang a friend when came after nearly an hour, tried jump starting and it worked! At this point I was sure it was the battery. So I decided to keep the engine running when I got to my son’s school just in case.

Then I drove to my mate’s garage, picked up a brand new battery from Eurocarparts, replaced the battery, tried starting and it started! Thought finally! When I came back to the car after 5mins, guess what??? The problem is back again! Car won’t start! To say I was devastated at that point will be an understatement as you know how expensive these batteries are. At this point I decided to clear all codes and do a rescan which came up with much less codes: 2ACB; 30BA; 30BB; 2E85 & 40B4

2 days later, I read a post which suggested checking the ECU fuse (F4), I had already changed the dme relay without any joy by the way. So I swapped the F4 with another 10A fuse and the vehicle starts! Tried 2 more times and each time it starts. But obviously I was still nervous. After about 30mins, tried starting again and it won’t start! Tried swapping the F4 with 2 other fuses without luck then tried a third fuse and it starts so managed to drive it home which is about 3miles away. When I got home, I switch it off and immediately tried starting again and it was fine. Then after 5mins the problem returns, won’t start!

Below is a list of interventions which seems to have worked at least once:

1) replaced fuel pump fuse - worked for about 3wks
2) replaced earth strap - worked for about a day
3) jump start - worked once
5) changed battery - started once

As I mentioned before, changing the ecu relay didn’t make any difference at all.

Sorry for the too many messages but it’s a puzzle I just can’t get my head around.

Any help will be greatly appreciated, thanks

 

Welcome aboard Michael,

I'm no mechanic and someone will be along soon who knows what they're talking about.
However on reading your post I can't help but feel that the ignition barrel may be worthy of investigation.

Kindest Regards
Carl.

 

Thanks Carl, I’ll get the barrel checked out, will update you if I have any luck