I'm puzzled.
I went to start the car; it ran for 2 minutes, then died. Wouldn't restart.
After verifying no spark and no fuel, I replaced the following:
Spark Plugs
Crankshaft Position Sensor
Coil
Main Relay
__________________________________________________ ______
I checked the DME Pins according to the following checklist:
For the engine to run the following conditions must be met:
Power on DME pins:
27 Start Input
18 Un-switched Power input
37 Power Input from Main Relay
Ground on DME pins 2, 14, 19, 24
Timing data from the CPS on DME pins 47 & 48 from a rotating engine
To have spark power must be present at the coil positive and ground pulses
from the DME's pin 1 must reach the coil negative. Power to the coil is
controlled by the ignition switch via C101. When checking for spark, use the
output lead from the coil to eliminate the distributor, rotor and plug wires.
To have injector firing power must be present at each injector and ground
pulses from the DME's pin 16 (Bank1) and pin 17 (Bank2) must reach the
respective injector bank. Note that the injectors are wired as two banks of
three. With cylinder 1,3,5 being bank 1 and 2,4,6 being bank 2. Power to the
injectors is controlled by the main relay.
The fuel pump relay must have power on pin 86 (relay coil) from the main relay
output (pin 87) and power on pin 30. The DME will ground pin 85 to turn on the
relay and power the pump(s) via pin 87. Of the above, only the fuel pump power
is fused. So if the there's power at pin 87, but not at the pump, check fuse
11.
The main relay and DME pin 18 receive power from the smaller of the to wires
that connect to the battery's positive terminal. That wire incorporates an
in-line fuse. When the DME is presented with a start signal, it grounds the
main relay pin 85 and furnishes power to the fuel pump relay, injectors, and
DME.
Troubleshooting:
Disconnect the battery and the DME cable. Then:
1) Disconnect the coil negative and check continuity from that connector to
DME pin 1. Also verify that from DME pin 1 to ground is an open circuit.
2) Check the resistance across DME 47 & 48, which should be 500-560
ohms. If the CPS is dismounted, the resistance can be seen to change
from about 500 to 540-540 when a ferrous object is brought to the face of the
sensor. Neither pin should be grounded.
3) Check for continuity from DME 36 to main relay 85 and from DME 3 to fuel
pump relay 85.
Reconnect the coil, remount the CPS (air gap should be 0.040"), plug the
relays back in, reconnect the DME, and connect the battery. Then do the
following checks:
1) With the key off, verify that power is present at DME pin 18 and main relay
86 & 30.
2) With the key on, verify that power is present at DME pin 27 and pin
18. Power to pin 18 is from the main relay and there should be power to the
injectors and fuel pump relay.
3) With the key on, verify that no voltage is present at the DME grounds (2,
14, 19, 24).
4) Verify that power is present at the coil positive and at fuel pump relay
pin 30. Those get switched power from the ignition switch via C101.
The engine will start and run (if poorly) with only those connections to the
DME in place. The other signals from Cylinder ID, AFM, temp sensor, etc., are
necessary for proper operation. But they won't prevent the engine from firing.
IMPORTANT:
A power check means seeing a voltage within about a tenth of a volt of what
you measure across the batter terminals, which should be at least 12.6v on a
charged battery.
A continuity check means seeing less that 1 ohm of resistance.
An open circuit means seeing a resistance of at least 100k ohms.
A good quality auto-ranging Digital Multimeter will make these tests much
easier.
_____________________________________________
All connections to DME appear to be good according to the test procedure above.
After checking DME, there was no power to the fuel pump, at the pump. (checked with volt meter)
I then installed a new Main Relay, it started!
But sadly, the Check Engine light flickered on, and the car stuttered, RPM's dropped with my foot on the gas. Then the Check Engine light came on again and it died. (the new relay could be dumb luck that it started)
I have the fuel pump relay and O2 sensor heater relay on order, they should arrive next thursday.
What could be happening here? Can I read a code to better understand where the problem is coming from on Motronic 1.1?
Is this the sign of a loose connection, corrosion, Bad DME/ECU?
Could it be a bad connection on the ignition switch?
Coolant temp sensor?
I'm starting to run out of ideas. I've attached a drawing, a mind map if you will.
I went to start the car; it ran for 2 minutes, then died. Wouldn't restart.
After verifying no spark and no fuel, I replaced the following:
Spark Plugs
Crankshaft Position Sensor
Coil
Main Relay
__________________________________________________ ______
I checked the DME Pins according to the following checklist:
For the engine to run the following conditions must be met:
Power on DME pins:
27 Start Input
18 Un-switched Power input
37 Power Input from Main Relay
Ground on DME pins 2, 14, 19, 24
Timing data from the CPS on DME pins 47 & 48 from a rotating engine
To have spark power must be present at the coil positive and ground pulses
from the DME's pin 1 must reach the coil negative. Power to the coil is
controlled by the ignition switch via C101. When checking for spark, use the
output lead from the coil to eliminate the distributor, rotor and plug wires.
To have injector firing power must be present at each injector and ground
pulses from the DME's pin 16 (Bank1) and pin 17 (Bank2) must reach the
respective injector bank. Note that the injectors are wired as two banks of
three. With cylinder 1,3,5 being bank 1 and 2,4,6 being bank 2. Power to the
injectors is controlled by the main relay.
The fuel pump relay must have power on pin 86 (relay coil) from the main relay
output (pin 87) and power on pin 30. The DME will ground pin 85 to turn on the
relay and power the pump(s) via pin 87. Of the above, only the fuel pump power
is fused. So if the there's power at pin 87, but not at the pump, check fuse
11.
The main relay and DME pin 18 receive power from the smaller of the to wires
that connect to the battery's positive terminal. That wire incorporates an
in-line fuse. When the DME is presented with a start signal, it grounds the
main relay pin 85 and furnishes power to the fuel pump relay, injectors, and
DME.
Troubleshooting:
Disconnect the battery and the DME cable. Then:
1) Disconnect the coil negative and check continuity from that connector to
DME pin 1. Also verify that from DME pin 1 to ground is an open circuit.
2) Check the resistance across DME 47 & 48, which should be 500-560
ohms. If the CPS is dismounted, the resistance can be seen to change
from about 500 to 540-540 when a ferrous object is brought to the face of the
sensor. Neither pin should be grounded.
3) Check for continuity from DME 36 to main relay 85 and from DME 3 to fuel
pump relay 85.
Reconnect the coil, remount the CPS (air gap should be 0.040"), plug the
relays back in, reconnect the DME, and connect the battery. Then do the
following checks:
1) With the key off, verify that power is present at DME pin 18 and main relay
86 & 30.
2) With the key on, verify that power is present at DME pin 27 and pin
18. Power to pin 18 is from the main relay and there should be power to the
injectors and fuel pump relay.
3) With the key on, verify that no voltage is present at the DME grounds (2,
14, 19, 24).
4) Verify that power is present at the coil positive and at fuel pump relay
pin 30. Those get switched power from the ignition switch via C101.
The engine will start and run (if poorly) with only those connections to the
DME in place. The other signals from Cylinder ID, AFM, temp sensor, etc., are
necessary for proper operation. But they won't prevent the engine from firing.
IMPORTANT:
A power check means seeing a voltage within about a tenth of a volt of what
you measure across the batter terminals, which should be at least 12.6v on a
charged battery.
A continuity check means seeing less that 1 ohm of resistance.
An open circuit means seeing a resistance of at least 100k ohms.
A good quality auto-ranging Digital Multimeter will make these tests much
easier.
_____________________________________________
All connections to DME appear to be good according to the test procedure above.
After checking DME, there was no power to the fuel pump, at the pump. (checked with volt meter)
I then installed a new Main Relay, it started!
But sadly, the Check Engine light flickered on, and the car stuttered, RPM's dropped with my foot on the gas. Then the Check Engine light came on again and it died. (the new relay could be dumb luck that it started)
I have the fuel pump relay and O2 sensor heater relay on order, they should arrive next thursday.
What could be happening here? Can I read a code to better understand where the problem is coming from on Motronic 1.1?
Is this the sign of a loose connection, corrosion, Bad DME/ECU?
Could it be a bad connection on the ignition switch?
Coolant temp sensor?
I'm starting to run out of ideas. I've attached a drawing, a mind map if you will.
Attached Files
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