smellmycheese Posted January 21, 2017 Share Posted January 21, 2017 My much loved bmw is playing up again.It's a 1986 728i auto. Sometimes I'll be out and if I stop at the shops,when I get back in it won't start. Full dash lights just absolutely nothing. Battery is brand new. Alternator charging ok. Earth checked and extra one added. As soon as you jump it from another car it'll start which made me think earth problem but no. Tried two new batteries from other cars but no. Doing my head right in tbh.... Link to comment Share on other sites More sharing options...
Station Posted January 21, 2017 Share Posted January 21, 2017 Put jump cable from battery negative to body or engine. Or Check ignition switch.It could be starter as well. saucedoctor 1 Link to comment Share on other sites More sharing options...
JeeExEll Posted January 21, 2017 Share Posted January 21, 2017 Select park or neutral. Link to comment Share on other sites More sharing options...
smellmycheese Posted January 21, 2017 Author Share Posted January 21, 2017 Put jump cable from battery negative to body or engine. Or Check ignition switch.It could be starter as well.Tried this. Thought about ignition but goes as soon as jumped Link to comment Share on other sites More sharing options...
smellmycheese Posted January 21, 2017 Author Share Posted January 21, 2017 Select park or neutral.Tried over and over Link to comment Share on other sites More sharing options...
BavarianRetro Posted January 21, 2017 Share Posted January 21, 2017 Have you tried to start it from the diagnostic socket? Link to comment Share on other sites More sharing options...
Station Posted January 21, 2017 Share Posted January 21, 2017 It sounds like the jump start is giving it more amps from a second battery to kick the starter into motion. Link to comment Share on other sites More sharing options...
smellmycheese Posted January 21, 2017 Author Share Posted January 21, 2017 Have you tried to start it from the diagnostic socket?You've lost me there Link to comment Share on other sites More sharing options...
JeeExEll Posted January 21, 2017 Share Posted January 21, 2017 Was joking, but it could be an intermittent fault with the gearbox ignition lock-out switchy thing though, or at a connector to do with it. I had a e34 auto a while back which was parked up for a year. The gear selector mechanism siezed up during that time and caused all sorts of problems. Intermittent problems are a bugger to find, as you well know. Edit, have just re-read your first post. It's not really intermittent. As it needs two batteries in parallel to start every time it looks like your BM needs LOTS of current to start.One battery would probably still be enough to eventually overcome a random might-work, might-not-work control circuit problem. As it starts EVERY time when jumped from another battery my gut feeling would be to get the starter motor checked out. But first check the thick cable and every connection going to it. Do these BMWs have a ballast resistor which may have gone high resistance? And post any developments. You have a waftobarge we don't see very often any more Link to comment Share on other sites More sharing options...
BavarianRetro Posted January 21, 2017 Share Posted January 21, 2017 Sorry. The diagnostic connector in the engine bay. Where you reset the service lights? If you bridge pins 11 and 14 the starter will operate. Be aware though that it'll operate irrespective of the inhibitor switch, so it'll start in gear. So if it starts from the diagnostic connector, it means that the starter motor and its wiring/earthing is in order and you need to look at the ignition switch/inhibitor switch side of things. spike60, Magnificent Rustbucket, ShiteRider and 5 others 8 Link to comment Share on other sites More sharing options...
smellmycheese Posted January 21, 2017 Author Share Posted January 21, 2017 Thanks for the help all. Boyd I'll try that tomorrow. She looks good on the style 5's I bought from you. Will post the outcome JeeExEll 1 Link to comment Share on other sites More sharing options...
Dead_E23 Posted January 21, 2017 Share Posted January 21, 2017 If BavarianRetro's pin-shorting method points the finger of suspicion at the starter motor, see if you can give the starter solenoid a sharp tap with something and try it again. (The 'something' could be placing the tip of a long screwdriver on it and administering the tap to the other end). Removing the starter motor from an M30 engine is tricky - mine needs to come off, but one of the bolts is very difficult to get at. I've read that you can reach down the back of the inlet manifold with a skinny spanner and get at it that way, but have not tried it yet. If that fails, I suspect the next line of attack is for the inlet manifold to come off, which will be a PITA. Iirc, my Chilton manual suggests the offending bolt can be loosened with a narrow walled socket. After a very uncomfortable hour or two trying, I found this not to be the case. JeeExEll 1 Link to comment Share on other sites More sharing options...
BavarianRetro Posted January 21, 2017 Share Posted January 21, 2017 The spanner in the bootlid toolkit is the one for the starter motor. JeeExEll, mercedade and Dead_E23 3 Link to comment Share on other sites More sharing options...
spike60 Posted January 22, 2017 Share Posted January 22, 2017 The spanner in the bootlid toolkit is the one for the starter motor.Is that to take it off or hit it with? Link to comment Share on other sites More sharing options...
BavarianRetro Posted January 22, 2017 Share Posted January 22, 2017 Either. You can drop the gearbox cross member and using a variety of extensions, wobblies, universal joints etc. get to the bolt too. Link to comment Share on other sites More sharing options...
smellmycheese Posted March 7, 2017 Author Share Posted March 7, 2017 If BavarianRetro's pin-shorting method points the finger of suspicion at the starter motor, see if you can give the starter solenoid a sharp tap with something and try it again. (The 'something' could be placing the tip of a long screwdriver on it and administering the tap to the other end). Removing the starter motor from an M30 engine is tricky - mine needs to come off, but one of the bolts is very difficult to get at. I've read that you can reach down the back of the inlet manifold with a skinny spanner and get at it that way, but have not tried it yet. If that fails, I suspect the next line of attack is for the inlet manifold to come off, which will be a PITA. Iirc, my Chilton manual suggests the offending bolt can be loosened with a narrow walled socket. After a very uncomfortable hour or two trying, I found this not to be the case.Where is the starter solenoid? Link to comment Share on other sites More sharing options...
BavarianRetro Posted March 7, 2017 Share Posted March 7, 2017 On the starter motor. Link to comment Share on other sites More sharing options...
Dead_E23 Posted March 7, 2017 Share Posted March 7, 2017 ,,,which is tucked away under the inlet manifold. This picture shows it well, but it's not as easy to see when the engine's in the car. You can feel the wiring on the solenoid if you grope around a bit - it may even be possible to transmit blows to the solenoid using a big screwdriver through the holes in the manifold, but I haven't looked at mine recently enough to remember. ETA: looking at the flywheel in that picture has made me realise I could inspect it using a tiny USB borescope through the hole for the crankshaft position sensor and without disturbing the starter motor. I suspect the timing pin has fallen out of mine. Link to comment Share on other sites More sharing options...
smellmycheese Posted March 8, 2017 Author Share Posted March 8, 2017 OK it's not the starter! The diagram I had of the diagnostic plug was back to front so now I've bridged 11 and 14 and she starts! Result. The relay is clicking when ignition is turned so I'm thinking it must be this??? Link to comment Share on other sites More sharing options...
smellmycheese Posted March 8, 2017 Author Share Posted March 8, 2017 OK it's not the starter! The diagram I had of the diagnostic plug was back to front so now I've bridged 11 and 14 and she starts! Result. The relay is clicking when ignition is turned so I'm thinking it must be this??? Link to comment Share on other sites More sharing options...
The Reverend Bluejeans Posted March 8, 2017 Share Posted March 8, 2017 There is a starter inhibitor relay up under the dash - follow the wires from the switch on the sector gate. It's been 15 years since I worked on an E23 so I don't know where it is exactly. Link to comment Share on other sites More sharing options...
The Reverend Bluejeans Posted March 8, 2017 Share Posted March 8, 2017 Just had a thought - the relay may be within the centre console but you may find the bracket that secures the push button switch to the selector has come loose. Link to comment Share on other sites More sharing options...
BavarianRetro Posted March 8, 2017 Share Posted March 8, 2017 Three speed or four speed? Link to comment Share on other sites More sharing options...
smellmycheese Posted March 8, 2017 Author Share Posted March 8, 2017 Three speed or four speed?Not sure tbh. 728i. Link to comment Share on other sites More sharing options...
BavarianRetro Posted March 8, 2017 Share Posted March 8, 2017 Year? Link to comment Share on other sites More sharing options...
smellmycheese Posted March 8, 2017 Author Share Posted March 8, 2017 Year?87 Link to comment Share on other sites More sharing options...
BavarianRetro Posted March 9, 2017 Share Posted March 9, 2017 If it starts from the diag socket, it has to be something in the ignition switch, inhibitor switch, starter motor circuit. It'll be pretty simple to trace with a multimeter. To begin, try moving the gear selector slowly through the box as you hold the key on start. Link to comment Share on other sites More sharing options...
The Reverend Bluejeans Posted March 9, 2017 Share Posted March 9, 2017 86/87 will be 4HP22 non switchable on a 728i. Link to comment Share on other sites More sharing options...
smellmycheese Posted March 9, 2017 Author Share Posted March 9, 2017 86/87 will be 4HP22 non switchable on a 728i.I'm lost again. What's one of them? Link to comment Share on other sites More sharing options...
The Reverend Bluejeans Posted March 9, 2017 Share Posted March 9, 2017 4HP22 - 4 speed ZF auto box. 728i's were not offered the switchable sport/economy version because they didn't have engine management. Link to comment Share on other sites More sharing options...
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