Re: <E28> 535i-No start/electrical Suggestions

[Pearson-Franks Family <pearsonf@xxxxxxxxxxxxxxx>]

Hi, Scott!

Dang!  Ya hate it when they do that!  And, they do.  Your
troubleshooting is good, but I wait with bated breathe on
your next measurements.  On first read, I would suspect
your 'main' relay.  You state it is 'good' - does that mean
you have replaced it with a known good, same last three
part number (they care) component?  Pin 35 to the ECU goes
straight to pin 87 on the main relay.

The main relay in turn is driven by the output of the on-
board computer - driven in turn by fuse 5.  If you are
certain the 'main' relay is OK (and all connections to it)
you can try jumping +12v to the main relay coil at a
number of spots, the easiest to find being C202, a 13 pin
connector to the left of the steering column, a .75mm
green wire.

This is somewhat at odds with the schematic on page 7-41
of your Bentley, but I trust the Electrical Troubleshooting
Manual (ECM) more.  Bentley shows the schematic for an '87.
If you plan on having the car for a while, get the ECM!

You may notice I ignored the observation that you could not
detect the 960 ohms of each of the sensors at the ECU
connector.  I am willing to bet that you have already solved
that one - the key data point in my book is the lack of +12
at pin 35 to the ECU.

Have fun!  Larry F.

>Date: Sun, 10 Oct 1999 14:47:34 -0500
>From: Scott Rassier <srassier@domain.elided>
>Subject: E28 535i-No start/electrical problem
>
>Hello everyone-I am somewhat new to using the digest so please forgive me
>if I go about my request for information incorrectly. I have a 86 535i that
>is currently dead. The vehicle died just as the clutch engaged at an
>intersection and failed to restart. It died much like it would if driven by
>someone inexperienced with a manual transmission. It didn't exhibit any
>sort of jerk though. The same thing happened a week earlier, but the
>vehicle started once again after a few minutes. The car now sits in my
>garage and has the following symptoms.
>
>- -No spark
>- -starter goes and engine turns (belts, fans, etc. spin)
>- -12 volts can be found at the coil and the injectors.
>- -fuses are all good
>- -main relay is good
>- -fuel relay seems good?
>- -speed sensor is displaying proper read out (when tested from within
>engine)
>- -reference sensor is displaying proper read out (when tested from within
>engine)
>- -fuel seems to be present, but I am unsure if it is coming from the
>injectors or the cold start valve. I am uncertain if the cold start valve
>would supply fuel if the injectors were not functioning?
>
>When testing the readouts at the Motronic the following was found.
>- -at pin 35( voltage supply to control unit) battery voltage was not present
>(Bently suggests 12V)
>- -at pins 25 and 26 (Reference senors) no resistance was seen (Bentley
>suggests 960 ohms)
>- -at pins 8 and 27 (Engine speed sensor) no resistance was seen (Bentley
>suggests 960 ohms)
>- -all grounds seem to check out
>I was not able to check the fuel pump or injectors. I should have that
>information shortly.
>If anyone has any suggestions as to where to go next I would greatly
>appreciate it. Thank you very much.
>
>
>Sincerely,
>
>Scott Rassier

Larry Franks
Issaquah, Washington
'95 540i/6
'86 535i
'83 245 GLT  (Swedish iron)

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