Need Help--Electrical/starting problem
 

I have an intermittent starting problem. Sometimes it starts fine. Sometimes I will get just a click like a dead battery. I can shut it off and start it immediately after that and it starts fine. Once in a while there isn't even a click and none of the dash lights come on. I have jump started it twice. First time it ran until I reved it and then it died. I jumped it again, drove it 4 miles with no issue and got home, turned it off and it started fine.

What I have done so far:

This started with a dead battery. Battery was bad. So was first replacement.
I have the correct and good battery installed
Checked for corrosion at front and back battery cable connections.
Turned on air on max and bright lights when it was running- alternator adjusted.
Monitored the alternator for spikes or dropping below min spec--no issue.
Let it sit for 8 hours checked battery status, no drain.
When it won't start there is no voltage under the hood but voltage at the battery is normal. Right now it is reading the same voltage at the battery and under the hood.

I do have a battery cut off switch but I can't make it malfunction. If I can make it happen again I will check if there is voltable on both sides. I am using a multimeter for testing voltage. I am aware electronics are sensitive and jumped it properly.

Any idea what troubleshooting I can do or what the problem might be?

You say when it doesn't start you don't have power under the hood do you mean at the boost terminal ?? Don't forget to check grounds too. A test light might be better to start with for checking battery cables and grounds.

Did you scan the vehicle when you had the no start. One very common issue with age on these BMWs is the EWS (vehicle immobilizer module/electronic Drive away protection) unit the vehicle. If defective it will not let the vehicle receive its start signal. You will have to have a scanner to check it.

The contacts in the ignition switch go bad. Very common BMW issue. The contact block is separate from the key way and is only around $25. Just remove the steering column trim to access. You could also disassemble to inspect

:iagree:

There's a test with the vanity mirror when the ignition switch is bad. I believe the vanity light over the mirror will not light up if the ignition switch is bad.

:iagree:

When weird electrical issues pop up on start cycles, look at the Ign S/W as that issue is common across all vehicles since they invented the damn thing in the 60's.. Older models would smoke as the carbon pins shorted out. Now days you get nothing. Hi turns in every parts line across all manufacturers.

As posted, many items that energize with key on, will not work as the s/w fails.

Examples: No voltage moves to starter, ignition, accessories, etc, as the switch is the source of the circuit connection failure. GM actually makes a specialty tool to eliminate that failure test.

At times you can just smack the s/w and it will work for a few cycles until total failure.

Yes, at the boost terminals. Have checked all connections positive and ground. Using multimeter so I can see actual amount of voltage

Hi David.X5

Is this the component you are referring to

http://i.ebayimg.com/images/g/wR8AAO...mBC/s-l400.jpg

New Steering Ignition Switch Starter Fit BMW E39 540 E38 750 E53 x5 61326901962 | eBay

The PN for the above image is 61326901962 and is about $20

I too experience this no-start anomoly sometimes. It resolves itself with another cycle of the key to start.

Another question, does this module work for every key? Any install tips appreciated.

Thanks,

Mike

I really appreciate the input. I hate electrical problems so I start out irritated. I have done the disassembly 4 times as I thought I found the problem each time. I have reached the limit of my patience.

I don't have any of the usual ignition switch symptoms. When I have a no start condition there are no dash lights at all, nothing works, it is as if the battery is removed. However, there is 12+ volts at the battery but 0 voltage at the terminals under the hood.
To the best of my knowledge the cables from the battery to the terminals under the hood have no breaks, one solid wire and go directly to the under hood terminals. Can a bad ignition switch also cause my problem?

If I am not off base, I can think of only two possibilities. The cutoff switch in the back is sometimes breaking the circuit even though it is in the correct position or the backside of the positive terminal under the hood is doing the same thing.

This has happened several times with no common circumstances. The last time I was at the wheel alignment shop. It started normally and drove normally going there. When tech unlocked it to take it in I saw angel eyes come on as I have them wired and were normal brightness. When tech tried to start it. there was nothing. No power to anything and multimeter at underhood terminals was 0. No angel eyes, nothing. I called AAA and it was going to be 1.5 hours. I waited a half hour and decided to jump it. It started and after letting the engine run for a few minutes I decided to see if I could make it home. Got home, shut if off and it started normally. I won't have to have my hair cut for a very long time.

Given the stated facts - 12v on the battery and no volts at the jump terminals under the hood (bonnet) - the only credible theory is that something is wrong with your battery isolator, despite the appearance that its ok. Or there really is a break in the main cable (very unlikely).

Checking the input and output on the battery isolator switch next time the fault occurs will be very telling... :D