[alfa] The Spider Lives!

["Daegrigg (Don)" <daegrigg@xxxxxxxxxxx>]

Eureka!

The spider is running.  The key was John Fielding's admonition, no spark no
fuel.  The connections at the coil terminals were just loose enough combined
with the car sitting in the carport for three months to make for bad
connections.  No spark!.  Cleaned and tightened and she came right to life.

Thanks,  John and everyone else who offered help.

Now to the 164 water pump that started leaking yesterday.


Don

----- Original Message -----
From: John Fielding <johnf@domain.elided>
To: Daegrigg (Don) <daegrigg@domain.elided>
Cc: <alfa-digest@domain.elided>
Sent: Tuesday, October 14, 2003 12:06 PM
Subject: [alfa] RE: 86 Spider no start


> Hi Don,
>
> Your AR Spider has the Bosch Motronic system, a derivative of the
L-Jetronic used on
> earlier vehicles.  It so happens that I know an awful lot about L-Jetronic
& Motronic
> especially the AR ones.  The only difference between the Motronic used
here and the USA
> version was the inclusion of an O2 sensor in the USA spec vehicles.
>
> You have no fuel injector pulses because you have no spark!
>
> The L-Jetronic used the pulses from the coil -ve terminal to clock the
injector ECU to
> give engine speed information.  If the ignition is bad the fuel will not
be pulsed.
>
> The Motronic design built on the L-Jet design with a number of subtle
changes, the main
> one is that is there is no switch in the AFM to energise the fuel pump.
Bosch changed
> this when the Motronic was designed, instead the ECU has to see valid
crank sensor signals
> before the pump relay is turned on.  The fuel injection side is identical
to the earlier
> L-Jetronic, except the speed signal which used to come from the ignition
coil -ve terminal
> now comes from the coil driver trigger.
>
> The ignition portion of the Motronic ECU needs two signals from the crank
sensors.  One is
> the rpm or speed signal which is the magnetic pickup that sees the starter
teeth on the
> flywheel.  There are 131 teeth on the starter ring gear, so for every
revolution the ECU
> expects to see 131 pulses.  When it has "counted" 131 pulses it knows that
1 complete
> revolution has occured, but it has no idea what the crank shaft angular
position is.
> This is gets from the second magnetic pickup.
>
> The second signal is called the "Reset" transducer and has an identical
> magnetic pickup but this one sees a single pin or lump on the flywheel.
This gives
> crankshaft angular position information.  On the '86 Spider the pin occurs
at 57.5 degrees
> before #1 TDC.  The Motronic computes the ignition advance using this
"epoch pulse" to
> define where #1 TDC is and from the rpm signal to compute how fast
> the engine is turning.  (There is a limited built in default mode where it
can provide a
> fixed idle timing and injector pulse width if the rpm signal is out of
specification but
> this does not allow the engine to be revved up).
>
> In order for the ECU to start looking for pulses several things need to
happen, apart from
> being powered up by the ignition switch being turned on.  There is no
"Keep-Alive" power
> connected to the earlier Motronic ECU's such as yours, this only occurred
with the later
> versions.
>
> 1).    The starter solenoid activating signal is routed to the ECU Pin 4.
When this line
> goes above 6V the ECU switches on and starts looking for rpm signals from
the starter
> ring gear.  (This fixes the ignition timing at a low advance and a fixed
injector pulse
> width - computed from water temeraure - until the engine speed exceeds
approx. 500rpm).
>
> 2).    If the rpm signal is present and above 100rpm the ECU then goes and
looks for
> Reset pulses which occur once per revolution.  If these are both within
given parameters
> the fuel pump relay is pulled in and the ignition coil driver stages are
powered up.
> Note: Cranking with a flat battery sometimes won't boot the ECU/fuel pump
as the starter
> signal is below 6V and the engine is turning too slowly!
>
> 3).    If the rpm signal is too slow the ECU assumes the engine has
stalled and shut down
> until the starter signal is again present.  This kills the spark and the
fuel pump relay.
>
> 4).    There a limited start stategy designed in that allows the vehicle
to be push
> started.  After seeing rpm AND reset signals for longer than 1s the ECU
will start
> computing the spark timing and then fire the coil.  Note: There does not
need to be a
> starter signal present for this.
>
> The most likely cause is the magnetic pickups.  These give endless
problems through poor
> connections and AR is not alone in this.   BMW & Porsche cars use the same
Motronic system
> and 99% of all non-start cases I have worked on the magnetic pickups
connectors are the
> culprit.  The actual transducers rarely give trouble but the 3 pin
connectos are a PITA
> when they become corroded.  (Recently I had to travel to Mozambique to try
and get an old
> Porsche 944 running.  On this car both magnetic sensors were dead, because
the swinging
> casting that sets the correct clearance between the sensors tips and the
flywheel had been
> swung too far and the flywheel nibbled the ends away so damaging the
sesnsors.
> Fortunately AR don't use such a stupid setup!)
>
> Also if you accidentally get the two connectors mixed up the ECU doesn't
understand the
> incorrect signals and will stay in shut-down mode with a resulting
no-start.  A very
> common problem especially if the engine has been pulled and the connectors
are incorrectly
> attached to the wrong sensor.  Unfortunately Bosch didn't use different
connectors for the
> two so it is easy to get them mixed up.
>
> The possibilty of putting the flywheel back in the wrong place will not
result in a
> no-spark condition, you will get spark but it will be in the wrong place.
As you have no
> spark it isn't that.  IIRC the Alfa flywheel can only go on in one
position.
>
> I hope this helps to get your Spider running.
>
> I have the official Bosch/AR service manual on the Motronic system,  like
most service
> manuals, it contains a lot of errors!  I have verified the system on the
bench (I have a
> test jig for trouble shooting the Motronic ECU's I built some years ago)
and the
> measurements I made on a running engine to confirm the system parameters.
>
> Incidentally you may not have noticed this but Motronic actually does
this.
>
> The VVT solenoid on the inlet cam is controlled by the Motronic ECU.  It
switched over
> at approx. 1500rpm.  If the engine speed is increasing it pulls in the
relay that powers
> the solenoid.  If the engine speed is falling at 1500 rpm it drops out the
relay.  But at
> the switching point it switches off the coil driver whilst the VVT relay
is operated.
> This I noticed as a sudden drop in rev counter reading and then a sharp
recovery.  The AR
> rev counter is very damped and so you don't normally see this effect.  On
my race car I
> had an after market rev counter with not much damping and I wondered what
caused the
> needle to twitch, even tho' I was not using the VVT cam as I had Euro cams
fitted to the
> 2L engine. The VVT relay was disconnected but the ECU still cuts the spark
whilst it
> switches over!
>
> If you need pinout details please shout, I have this for the '86 Alfetta
which uses the
> same Motronic ECU, but no Lambda sesnsor.
>
> best regards
>
> John
> Durban
> South Africa
> Alfetta 1.8L turbo
> --
> to be removed from alfa, see /bin/digest-subs.cgi
> or email "unsubscribe alfa" to majordomo@domain.elided
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided