Starting problem

blackbirdxx · Post by **blackbirdxx** » Thu Jun 04, 2015 8:25 pm

Hi,
I have a starting problem. If I leave the car for a few days and turn the ignition the car refuses to start. I thought it was a parasitic draw at first but last night I checked the battery voltage and it read 12.4V which is more than enough to start the car. Strangely, Iâ€™m able to start the car via the diagnostic plug tripping terminals 11 and 14. The forums tell me that it is likely that starter switch is at fault, but I had it replaced 2 years ago. I know that if I fully charged the battery the car will start no problem. So, is the problem the starter or is there something else which may be at fault?
Anybody out there able to help me? Any assistance grateful received as usual.
1987 BMW 635CSI

Brucey · Post by **Brucey** » Thu Jun 04, 2015 9:04 pm

it sounds like the ignition switch itself. They do wear out.

cheers

Chris Wright · Post by **Chris Wright** » Sat Jun 06, 2015 5:27 am

Well, if you have the Auto tranny, jumping pin 11 and 14 in the diagnostic plug does bypass the start relay behind the drivers kick panel. Perhaps the contacts are dirty and not passing full voltage?

slofut · Post by **slofut** » Sat Jun 06, 2015 12:23 pm

Chris Wright wrote:Well, if you have the Auto tranny, jumping pin 11 and 14 in the diagnostic plug does bypass the start relay behind the drivers kick panel. Perhaps the contacts are dirty and not passing full voltage?

Chris,
If I may ask, what does this relay do? More than one function?
Bill

Chris Wright · Post by **Chris Wright** » Wed Jun 10, 2015 3:42 am

slofut wrote:
Chris Wright wrote:Well, if you have the Auto tranny, jumping pin 11 and 14 in the diagnostic plug does bypass the start relay behind the drivers kick panel. Perhaps the contacts are dirty and not passing full voltage?
Chris,
If I may ask, what does this relay do? More than one function?
Bill

The start relay is only on Automatics and is only energized when the gear shift is in park or neutral so the car won't start in gear. It sets inline between the ignition switch and the starter.

Brucey · Post by **Brucey** » Wed Jun 10, 2015 6:10 am

if you have an automatic then I agree the start relay is the more likely thing to go wrong. The gear selector switch is in the same circuit and will also inhibit the start relay, so that is worth looking at too.

cheers

blackbirdxx · Post by **blackbirdxx** » Mon Jun 15, 2015 1:13 pm

Thx guys,
I understand that the start relay is above the glove box (RHD vehicles). Above my glove box is a jumble of wires and relays. What's the best way to identify this relay??

thanks

Brucey · Post by **Brucey** » Mon Jun 15, 2015 6:45 pm

the best way to identify it is by the wire colours that go into the socket. You can find these on the relevant ETM diagram.

cheers

blackbirdxx · Post by **blackbirdxx** » Tue Jun 16, 2015 10:38 pm

Jumped terminals 30 and 87 on the start relay suggested by Chris in a past post and still the car won't crank. Does this mean that the ignition switch is faulty (despite it being replaced a couple of years ago)? or is there a switch within the auto shift mechanism I now should be checking. Car still cranks no prob jumping at the diagnostic plug.
thoughts appreciated

blackbirdxx · Post by **blackbirdxx** » Wed Jun 17, 2015 12:40 am

Just to reiterate, if I fully charge the battery, the car cranks no problem.

ron · Post by **ron** » Wed Jun 17, 2015 6:49 am

blackbirdxx wrote:Just to reiterate, if I fully charge the battery, the car cranks no problem.

Try a NEW battery.

Pod · Post by **Pod** » Wed Jun 17, 2015 9:57 am

ron wrote:
blackbirdxx wrote:Just to reiterate, if I fully charge the battery, the car cranks no problem.
Try a NEW battery.

Agree with Ron. Maybe the battery is on the point of failing and won't hold a sufficient charge to get things moving - even though it may show more than 12 volts. Voltage doesn't always mean the battery's good!

hornhospital · Post by **hornhospital** » Wed Jun 17, 2015 6:33 pm

This is a prime example of why you should LOAD TEST both the alternator and the battery when a low amperage situation is suspected. They can both check good with a voltmeter, but fail miserably when a load is applied.

blackbirdxx · Post by **blackbirdxx** » Thu Jun 18, 2015 2:20 pm

Thanks for responding guys but the battery is a powerful S5 bosch and only about a year old. Also, if its the battery that is failing then why is it cranking no problem when jumping at the diagnostic socket?? Its a mystery to me....
All suggestions most welcomed.

ron · Post by **ron** » Thu Jun 18, 2015 2:58 pm

I had a similar problem for about 2 years. It would ONLY start on jumping the diagnostic socket. Having replaced everything in the circuit I narrowed it down to the after-market immobiliser!

Once I removed that from the immobiliser/ alarm circuit I had no more problems.

Might be worth checking if you have an after-market system fitted.

blackbirdxx · Post by **blackbirdxx** » Sat Jun 20, 2015 10:08 pm

Thx Ron, good idea. Will investigate and report back.

Da_Hose · Post by **Da_Hose** » Sun Jun 21, 2015 7:40 am

Dealing with a similar issue.

The M6 acted like it had a dead battery today. Plugged in a start booster and no dice. Plugged in an external battery (from the RV), still no dice. Messed with the positive lead and it started

I believe the problem was corrosion in the positive terminal. I will post up the end result, but replacing the connector on the positive lead looks to have fixed things.

Joseh Joseh