Hi,
I've just picked an '89 535iS manual in need of some serious TLC, mainly welding to the sills. It was cheap but hopefully worth saving,
I'll know better once I can get it to start!! It's been stood for around 12years but apparently drove out of the garage less then 6mths
ago.
Initially when I put a battery on it all the dash lights came on and the immobiliser started beeping, before I'd even put the key in. I traced
this to a short through the alternator and once I disconnected the main lead this was OK.
Then it wouldn't turn over but briefly applying 12v directly to the starter kicked it into life and it now turns over on the key but still
won't start.
I have a spark and have fuel to the fuel rail but the injectors don't seem to be firing (plugs are dry). The DME relay is energising and
outputting 12v towards the ECU. Both injector terminals have 12v on them with ignition on but then both drop to around 6v when cranking, but the
battery was nearly flay by this point tbh. I'd expect one to stay around 12v and the other to pulse down to 0v, is this correct?
I seem to think it could be the ECU itself or more likely it isn't getting a signal it expects, like one from the CPS to say it's
cranking?
Any help would be appreciated,
Cheers
Nick
6v is quite possible on a flat battery.
Odd that not injected/wet the plugs before then though. Sounds like ther may be another gremlin
Get some easy start in it to get it firing for a start, if it's going to.
Then come back to the injector issue I say
Yeah it fires on Easy Start.
The ECU must be 'live' as it's passing 12v to the injectors, it's just not firing them with 0v pulses. But I don't know if
it's the ECU itself or a missing input like the crank position sensor.
[Edited on 11/9/17 by Nickp]
I would be checking CPS signal as next port of call
quote:
Originally posted by russbost
I would be checking CPS signal as next port of call
quote:
Originally posted by Nickp
Yeah it fires on Easy Start.
The ECU must be 'live' as it's passing 12v to the injectors, it's just not firing them with 0v pulses. But I don't know if it's the ECU itself or a missing input like the crank position sensor.
[Edited on 11/9/17 by Nickp]
quote:
Originally posted by ReMan
quote:
Originally posted by Nickp
Yeah it fires on Easy Start.
The ECU must be 'live' as it's passing 12v to the injectors, it's just not firing them with 0v pulses. But I don't know if it's the ECU itself or a missing input like the crank position sensor.
[Edited on 11/9/17 by Nickp]
That's good then, yuur nearly there
Don't guarantee ecu is working, the 12v could be from any live supply, as you mention the ecu may only ground the other side
No it doesn't. And I'm genuinely trying to be helpful, not clever or twatty
12v measured both sides would meant they have a 12 v supply (*not necesarilly from the ECU*) until the ECU grounds one side. and it activates the
injector
See this to indicate what I mean, I have no idea what the BMw is like
http://www.littlemetalshop.com/trailblazer/fuel-inj-wiring/133799695.gif
As said could well be the CPS,, fingers crossed.
quote:
Originally posted by ReMan
No it doesn't. And I'm genuinely trying to be helpful, not clever or twatty
12v measured both sides would meant they have a 12 v supply (*not necesarilly from the ECU*) until the ECU grounds one side. and it activates the injector
See this to indicate what I mean, I have no idea what the BMw is like
http://www.littlemetalshop.com/trailblazer/fuel-inj-wiring/133799695.gif
As said could well be the CPS,, fingers crossed.
I would suggested that disconnecting the injectors and using a noid light to check the feed and earthing of the injectors , it's not good practice to test using a test light due to possibly damaging the ECU . If you haven't got access to a noid light try a logic probe .
quote:
Originally posted by rusty nuts
I would suggested that disconnecting the injectors and using a noid light to check the feed and earthing of the injectors , it's not good practice to test using a test light due to possibly damaging the ECU . If you haven't got access to a noid light try a logic probe .
Hi if it runs on easy start crank sensor is ok as it sparks as you said injectors are not getting its earth pulse from the injectors it you have a 12v supply and perm earth and no pulse earth I reckon it's the Ecu u/s very common on BMW ecu to lose the injection pulse the Ecu should be repairable.
quote:
Originally posted by ian locostzx9rc2
Hi if it runs on easy start crank sensor is ok as it sparks as you said injectors are not getting its earth pulse from the injectors it you have a 12v supply and perm earth and no pulse earth I reckon it's the Ecu u/s very common on BMW ecu to lose the injection pulse the Ecu should be repairable.
Might be worth getting the old ECU checked out if not too much £££ as getting a used one to the same spec that is 100% OK might be tricky. At least then you can tick that off the possible cause list.
quote:
Originally posted by zetec
Might be worth getting the old ECU checked out if not too much £££ as getting a used one to the same spec that is 100% OK might be tricky. At least then you can tick that off the possible cause list.
I had at one time a test rig that connected in series with the ECU to test various sensors and injector operation , Not sure what happened to it but I think it was a Datacheck unit. It would test ECU operation as well.
quote:
Originally posted by rusty nuts
I had at one time a test rig that connected in series with the ECU to test various sensors and injector operation , Not sure what happened to it but I think it was a Datacheck unit. It would test ECU operation as well.
i'm pretty sure it'll be switched earths on it.
quote:
Originally posted by franky
i'm pretty sure it'll be switched earths on it.
quote:
Originally posted by Nickp
quote:
Originally posted by rusty nuts
I had at one time a test rig that connected in series with the ECU to test various sensors and injector operation , Not sure what happened to it but I think it was a Datacheck unit. It would test ECU operation as well.
Sounds ideal if you knew where it was
Was it car specific or did it have different ecu plugs?
quote:
Originally posted by rusty nuts
quote:
Originally posted by Nickp
quote:
Originally posted by rusty nuts
I had at one time a test rig that connected in series with the ECU to test various sensors and injector operation , Not sure what happened to it but I think it was a Datacheck unit. It would test ECU operation as well.
Sounds ideal if you knew where it was
Was it car specific or did it have different ecu plugs?
It was system specific rather than car specific. I have used it on 4 and 6 cylinder BMWs and Pegeot 205 GTIs that used Bosche systems but I can't remember which , possibly Motronic?