Thread: EFI Dramas Continue

Throttle Position Sensor (potentiometer)

To troubleshoot the Throttle Position Sensor, first disconnect
system power and then disconnect the EFI Cable Harness from the ECU.
Using an Ohmmeter, verify that resistance between terminals 3 and 25
is between 4000 and 6000 Ohms. Next, reconnect the EFI Cable Harness
to the ECU, and turn the ignition key switch "on". Take voltmeter reakdings
from pin 20 to ground. With the sensor in the throttle-closed position,
you should read 0.085 to 0.545 volts. With the sensor in the throttle-open
position, you should read 4.2 to 4.9 volts. In between these extremes,
turning the throttle position sensor should produce a smooth sweep of voltage readings.

RESULTS:
My Volt Readings:
Red Wire 10.6v
Red/Black 11.05
Yellow 11.05

NOTES:OHMs
ECU Terminals 3 & 25 OHMS should be 4000-6000 ohms
Results = 5.1k

Terminals pins 20 to ground 4.2 to 4.9 on open throttle
and 0.085 to 0.545 closed
Results = 0.35v to 4.8v

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Stepper Motor (Back of plenum)
My Volt Readings:
Grey/Blue 10.6
Orange 10.6
Green/White 10.5
Red/Green 10.5

Notes:Ohms
Check ohms acrtoss orange and blue &
then green and white, should show 40 to 60ohms and up to 70 when hot
green/white = 50
orange and blue 51

Results from ECU Terminals Stepper
Pins 28 & 29 = 53.5
Pins 1 & 26 = 53.5

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Fuel temp Sensor
RESULTS:
Red/black = 10.96v
Grey/white = 10.45
ohms @ plug = 1.970
WARNING: No Buzzing

ohms @ sensor =

ECU Readings
Results = 0, no buzz, unplug from ecu & 1.049 on 2k setting
Sensor Reading at pins 32(grey/white) & 25 should be 3880 of net
Results = 1.05 on 20k

19.83 with positive to red/black


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Water Temp Sensor
Blue/Green = 5.01v
Red/Black = 0
ohms @ plug 1.970
WARNING: No Buzz

2.72 resistance @ sensor (new sensor)

ECU ohms readings @ pins 35(blue/green) should be around 3760
results = 4.14 on 20k only
no buzzing

The Coolant Temperature Sensor should change resistance with heat, per the following specs.
10C (14°F) 9100-9300 Ohms
0C (32°F) 5700-5900 Ohms
20C (68°F) 2400-2600 Ohms
40C (104°F) 1100-1300 Ohms
60C (140°F) 500-700 Ohms
80C (176°F) 300-400 Ohms
100C (212°F) 150-200 Ohms

Results 2700 (good for temp today)

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Engine Speed sense circuit

white/black wire to -ve coil terminal = 0.01
Resistor Results = 6.91ohms
Read it reduces volts to around 7v to ecu??? WARNING: Does not reduce

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MAF Wires
Red/Black 0.11 (0n mv)
Blue/Green 48.9 (on mv)
Orange/Brown 12.97v
Blue/Red 5.02

ECU Pins 35 & Ground should be 0.3 to 0.6
Results = .003 (2v setting) & 4.5 on 200mv setting.
I have set the MAF to 1.3

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ECU
Ground to PIN 15 should be 10.5v
Results = 12.3

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Injectors-Left Bank
NO1:
Yellow/Blue = 0.08
Brown/Orange = 12.94
NO2:Same as above
NO3:Same as above
NO4:Same as above

Injectors-Right
NO1:
Yellow/Blue = 0.08
Brown/Orange = 12.94
NO2:Same as above
NO3:Same as above
NO4:Same as above

Minimum fuel flow per injector is 160-175cc per minute
using alcohol (for testing), or 180-195cc per minute using
gasoline, when tested at 36.25psi (2.54kgf/cm2) at 20C +/- 2C.(not tested yet)

Wiring faults on the injector circuits (and within the injectors)
can be tested for at the ECU connector. Turn the ignition off and
disconnect the ECU connector. Check the right bank of injectors by
measuring resistance between terminals 2 and 11. Check the left bank
of injectors by measuring resistance between terminals 2 and 13.
In both cases, an Ohmmeter reading of 4-4.5 Ohms is expected.
If the reading is 5-6 Ohms, suspect one bad fuel injector.
A reading of 8-9 Ohms could indicate two bad injectors, and a reading
of 16-17 Ohms could indicate three bad injectors. In any case, if the
overall circuit resistance isn't 4-4.5 Ohms, proceed to checking for
wiring faults or for open-circuit injectors.

RESULTS
Manual says 4.5ohms Mine = 4.2 @ pin 2 & 11 = 4.2
Each injectors = 15 ohms
right bank each inject wire = 0.16 to 0.17 depending on which wire
left bank = 0.15 & 0.17

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Coil Volts
white wire to +ve = 12.9
-ve while White connect = 12.89

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Still no go, im starting to wonder if the timing has jumped or i have a broken or warn cam shaft, but im sure this would have shown the compression test.

If it is still not going by end of next week i will need to replace the whole show with a motec system which i need to get for my stroker engine in the future anyway, but this wont be ready until xmas time, i was hoping to use this system and engine until have the rest set up, as i will have to waste money on dyno this engine,, either that or chuck a Edelbrock performer manifold & 500 carb for now of ebay for 830.

Any ideas anyone, appreciate any help.

Originally Posted by DiscoVan

I have been trying to get my 94 Disco going for a long time now (>12mths).

I did write about it sometime ago but can not find my post vis statistics, so i will start again.

Any help or advise much appreciated.

Wild guess ... your running 2 Forum names .... Look under Romaround

Disco 1's aren't that hard to diagnose.

Spark at each cylinder? Rotor buttons are known to burn through. Lucas amps are known to fail. Coils are known to fail. You can test for spark through the coil lead by rocking the rotor button while the pickup teeth are almost in alignment, ie the rotor tooth passes the pickup with movement. Test the rotor button by holding the coil lead above the rotor button with plastic pliers, see if a solid spark jumps to the brass strip.

Engine Speed sense circuit

white/black wire to -ve coil terminal = 0.01
Resistor Results = 6.91ohms
Read it reduces volts to around 7v to ecu??? WARNING: Does not reduce

A resistor only reduces voltage when a current flows through it. All that matters is that is present and connected.

Remember, no spark input, no injection. Your ECU detects ignition pulses and allows the fuel pump to run. Does the pump run for a moment after you stop cranking?

Timing chain slop: Rotate the crankshaft backwards and forwards, note how much movement there is without moving the distributor rotor. 10mm is OK, it will run.

Originally Posted by mike 90 RR

Wild guess ... your running 2 Forum names .... Look under Romaround

Yes, thank yopu for pointing that out. I had forgotten my other user, so i made this 1, just found that post yesterday arvo, so i will need to delete that user, i guess i do Romearound, lol...

Originally Posted by bee utey

Disco 1's aren't that hard to diagnose.

Spark at each cylinder? Rotor buttons are known to burn through. Lucas amps are known to fail. Coils are known to fail. You can test for spark through the coil lead by rocking the rotor button while the pickup teeth are almost in alignment, ie the rotor tooth passes the pickup with movement. Test the rotor button by holding the coil lead above the rotor button with plastic pliers, see if a solid spark jumps to the brass strip.

Hi bee utey, thanks for your reply,

I replaced all the leads, coil, plugs, cap plus pulled of every lead while running and check all with a plug earthed out on the the engine, all seem fine and ignites full well. I did not check the rotor button but i did try another 1 of a wreck i have, i also just tried your suggestion


A resistor only reduces voltage when a current flows through it. All that matters is that is present and connected.

Ok, i thought maybe the 10.5v at terminal 15 maybe a prob.

Remember, no spark input, no injection. Your ECU detects ignition pulses and allows the fuel pump to run. Does the pump run for a moment after you stop cranking?

Fuel pump runs when i first turn the ignition on and when i turn it off.

Timing chain slop: Rotate the crankshaft backwards and forwards, note how much movement there is without moving the distributor rotor. 10mm is OK, it will run.

Thanks for your tip, i have around 4-5mm max.

The battle continues, lol...

Dropped the plugs out again, all are dripping wet with fuel.

When it does run i dont hear the injectors tick, last LR i had was a 89RR in Swiss about 5years ago, i cant remember if the injectors ticked like Holden etc. It sure does seem like there stuck open.

I have replaced the injectors with second hand ones that were like new, ran like this with the old ones and these.

According to what i have read the only sensors that control the injector opening and timing is the Temp sensor, fuel temp sensor, the throttle position sensors.
I have double checked these this arvo the results are as follows:

TPS

RESULTS:
My Volt Readings:
Red Wire 10.6v
Red/Black 11.05
Yellow 11.05

NOTES:OHMs
ECU Terminals 3 & 25 OHMS should be 4000-6000 ohms
Results = 5.1k

Terminals pins 20 to ground 4.2 to 4.9 on open throttle
and 0.085 to 0.545 closed
Results = 0.35v to 4.8v (i just adjusted the throttle cable for now to 0.85 as i will need to re drill)

FTS

Fuel temp Sensor
RESULTS:
Red/black = 0
Grey/white = 4.95v
ohms @ plug = 1.99 (igntion On) 0 (Ignition Off)
WARNING: No Buzzing

ohms @ sensor = 1.99
sensor Buzz(resistance)

ECU Readings
Sensor Reading at pins 32(grey/white) & 25
Results = 5.2v
Results = NO REsistance whith ignition on! &
1.98 with ignition off & disconected at sensor
0.99 while sensor is connect

ECU PINS
5.12 original 94 ecu
5.27 of 97 ecu
NO RESISTANCE BUZZ ON 200!

CTS
Water Temp Sensor
Blue/Green = 5.2
ohms @ plug 1.97 (20k) with ignition off, no reading with ignition on
WARNING: No Buzz

NEW 1.98 resistance @ sensor in the motor (new sensor)
OLD 1.71 Out of the motor

ECU ohms readings @ pins 35(blue/green)
results = 4.14ohms on (20k)
Ignition on and ecu connected = 0.
no buzzing

ecu pins = 0 readings!
This could be the prob, but i have no idea if we should have a ohms reading
from the ecu alon for this sensor, tried both of my ecu, however its not to say i fried both of them some where along the lines .

Tnx...
Jason

The TPS input is 5Volts and the output to the ECU varies between about 0.5 volts and 4.8 or so when you hold the throttle open.
The third wire is an earth.
Either your multimeter is reading incorrectly or you are reading it incorrectly.

Regard sPhilip A.
BTW the MAF also controls injector duration once the engine is going, and it is the primary engine demand sensor unless you have o2 sensors.