[xj40] Re: ECU Location - Was NO START

John,
I took your advice and went back to the CPS. Checked continuity of red and
blue/black tracer wires from CPS to connector on ecu. This checked out ok.
Same for amp continuity test- checked ok. The black wire on the CPS goes to
ground and it checked ok for continuity as well. I checked for a “pulse”
from the cps by backprobing the cps connection to the ecu on the back of the
yellow ecu connector with connector plugged in to the ecu. With common probe
on my digital multi-meter to ground, and testing for small dc voltage (1 or
above), I get real small steady voltage (less than 1 volt) when cranking,
but no “pulsing”. Is the correct way to test for the pulsing? Resistance
between the red and blue/back tracer wire on the cps is about 1400 ohms. I
also pulled an injector connector and tested for “pulsing” when cranking.
With common to ground, both injector pins are at battery voltage with
ignition on, and drop to around 8 vdc when cranking and stay steady. Is
correct for testing for injector firing? I cleaned and applied dielectric
to the cps pin connector (at cps pigtail) Should I test for cps pulse with
the cps unplugged and probing the connector pins (to isolate a faulty
connection at the connector), or would this work? I believe that the cps
generates a small voltage when cranking by way of the magnetic coil,
recalling past list discussion on the issue. I did notice two or three water
drip marks on the bottom of the ecu. Looks like water may have been dripping
from the fan housing above as I see a bit of rust on the metal plate
separating the fan housing and the ecu?? I would guess small drips here, not
a lot of water. I’ve got to get the big cat running or my wife is going to
kill me!

Tom, '90 Sovereign 4.0

John wrote.
>By the way when I mentioned, in my earlier post, if you were sure about the

replacement CPS producing a pulse at the ECU, what I intended to convey was
that even a good CPS might not be delivering the pulse to the ECU. The
three pin plug and socket for this device might be suspect insofar as pins
making good contact. If this were the case then the ECU would not ‘see’ any
pulse.
When you locate the ECU and establish the appropriate pin numbers in the
connecting plugtop, check to make sure that the pulse is actually present.
If this is difficult, i.e., no assistant to crank while you check, a
continuity check should provide the same reading as the CPS. A failed ECU
seems to be a very rare event.


Chat with friends online, try MSN Messenger: http://messenger.msn.com

Tom
The CPS produce AC not DC, which can be measured with a mulitmeter with AC
selection. The correct output values from the CPS are 2.5 VAC at 1000 RPM
and 5.0 VAC at 3000 RPM. The resistance in the CPS coil should be between
1.25 and 1.45 kohms.

I guess you will need a oscilloscope to actually read the pulses during
cranking. I guess (not sure) the typical failure for a CPS will be a open
circuit in the coil, so if you read 1.4 kohms resistance in the coil, its
probably OK.

Check the CPS for correct position. The gap between the crank sensor core
and the toothed wheel, should be 0.020-0.040 in.

Good luck (with both your wife and cat)
Bjorn 1991 3.2----- Original Message -----
From: “Tom Keohan” tomkeohan@hotmail.com
To: jtarrant@bwt.ie
Cc: xj40@jag-lovers.org; djhaydel@cox.net
Sent: Tuesday, July 02, 2002 6:12 AM
Subject: [xj40] Re: ECU Location - Was NO START

John,
I took your advice and went back to the CPS. Checked continuity of red
and
blue/black tracer wires from CPS to connector on ecu. This checked out
ok.
Same for amp continuity test- checked ok. The black wire on the CPS goes
to
ground and it checked ok for continuity as well. I checked for a “pulse”
from the cps by backprobing the cps connection to the ecu on the back of
the
yellow ecu connector with connector plugged in to the ecu. With common
probe
on my digital multi-meter to ground, and testing for small dc voltage (1
or
above), I get real small steady voltage (less than 1 volt) when cranking,
but no “pulsing”. Is the correct way to test for the pulsing? Resistance
between the red and blue/back tracer wire on the cps is about 1400 ohms. I
also pulled an injector connector and tested for “pulsing” when cranking.
With common to ground, both injector pins are at battery voltage with
ignition on, and drop to around 8 vdc when cranking and stay steady. Is
correct for testing for injector firing? I cleaned and applied dielectric
to the cps pin connector (at cps pigtail) Should I test for cps pulse with
the cps unplugged and probing the connector pins (to isolate a faulty
connection at the connector), or would this work? I believe that the cps
generates a small voltage when cranking by way of the magnetic coil,
recalling past list discussion on the issue. I did notice two or three
water
drip marks on the bottom of the ecu. Looks like water may have been
dripping
from the fan housing above as I see a bit of rust on the metal plate
separating the fan housing and the ecu?? I would guess small drips here,
not
a lot of water. I’ve got to get the big cat running or my wife is going to
kill me!

Tom, '90 Sovereign 4.0

John wrote.

By the way when I mentioned, in my earlier post, if you were sure about
the

replacement CPS producing a pulse at the ECU, what I intended to convey
was

that even a good CPS might not be delivering the pulse to the ECU. The
three pin plug and socket for this device might be suspect insofar as
pins

making good contact. If this were the case then the ECU would not ‘see’
any

pulse.
When you locate the ECU and establish the appropriate pin numbers in the
connecting plugtop, check to make sure that the pulse is actually
present.

If this is difficult, i.e., no assistant to crank while you check, a
continuity check should provide the same reading as the CPS. A failed ECU
seems to be a very rare event.


Chat with friends online, try MSN Messenger: http://messenger.msn.com