Check engine light ON after servicing injectors

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kapilamuni

Active Member
Posts
550
Hi,
Got a new issue to address after servicing the injectors.(diesel, BMW engine 1997 MY)
Check engine light continues to stay ON . Read codes and got the following;

NANOCOM - EDC.APP - EDC faults file

ROAD SPEED SENSOR OUT OF EXPECTED RANGE
Type: HIGH CIRCUIT,MAJOR FAULT,LOGGED,CURRENT
RPM = 40
WATER TEMP = 80
OCCURRANCE = 10

NEEDLE LIFT SENSOR INVALID VALUE
Type: HIGH CIRCUIT,MAJOR FAULT,LOGGED,CURRENT,INTERMITTENT
RPM = 0
WATER TEMP = 171
OCCURRANCE = 14
---
AIR INTAKE TEMP INVALID VALUE
Type: TOO HIGH,LOGGED,CURRENT,INTERMITTENT
RPM = 0
BOOST PRESS. = 90
OCCURRANCE = 15

After clearing faults ( few times), last two faults disappeared.
Also, sometimes it goes 1500RPM in idle and stays there without coming down to usual 750 RPM.
No faults recorded on that though.
regards

---
 
Check you have not trapped the wire from number four injector in the manifold and cut it. Also look at IAT plug under front of manifold. Road speed sensor is an ABS wheel speed sensor playing up.
 
4th injector checked wire free n connected. IAT checked n replugged, no change.
Why is the idle RPM playing up? The engine seems bit noisy may be due to injectors playing better.
Yes, the check egine light is one looks like an injector.
 
kapilamuni said:
4th injector checked wire free n connected. IAT checked n replugged, no change.
Why is the idle RPM playing up? The engine seems bit noisy may be due to injectors playing better.
Yes, the check egine light is one looks like an injector.
Click to expand...
You may have damaged the wiring, do you have resistance between the contacts of number 4 injector?
 
I would think the number four injector has been damaged and the reason the engine is noisier is because the point of injection is not being adjusted correctly. What is the timing modulation at idle with a warm engine?
 
The T/modulation is between 46.1 to 63.3, most of the time around 61.(idling with hot engine).
Before the injector service, T/modulation was around 94, always.

Check engine light remains ON. The idling RPM is at 750 but if I press the accelerator it goes up and settles down at 1230 and thereafter fluctuates within 900 and 1200 in a shaky manner. It can only revert to 750 with shifting gear to D or R. Then it remains at 750 even if I shift to N or P. This happens most of the time if I press the accelerator.
This "non return to idling RPM" is felt even while driving too. When I slow down for traffic , the fluctuation is heard from the engine, bit annoying sometimes.
I could not check the resistance on the 4th injector yet. but confirm wiring in good shape.
 
kapilamuni said:
The T/modulation is between 46.1 to 63.3, most of the time around 61.(idling with hot engine).
Before the injector service, T/modulation was around 94, always.

Check engine light remains ON. The idling RPM is at 750 but if I press the accelerator it goes up and settles down at 1230 and thereafter fluctuates within 900 and 1200 in a shaky manner. It can only revert to 750 with shifting gear to D or R. Then it remains at 750 even if I shift to N or P. This happens most of the time if I press the accelerator.
This "non return to idling RPM" is felt even while driving too. When I slow down for traffic , the fluctuation is heard from the engine, bit annoying sometimes.
I could not check the resistance on the 4th injector yet. but confirm wiring in good shape.
Click to expand...
Mine looked ok but had failed inside at the coil
 
kapilamuni said:
The T/modulation is between 46.1 to 63.3, most of the time around 61.(idling with hot engine).
Before the injector service, T/modulation was around 94, always.

Check engine light remains ON. The idling RPM is at 750 but if I press the accelerator it goes up and settles down at 1230 and thereafter fluctuates within 900 and 1200 in a shaky manner. It can only revert to 750 with shifting gear to D or R. Then it remains at 750 even if I shift to N or P. This happens most of the time if I press the accelerator.
This "non return to idling RPM" is felt even while driving too. When I slow down for traffic , the fluctuation is heard from the engine, bit annoying sometimes.
I could not check the resistance on the 4th injector yet. but confirm wiring in good shape.
Click to expand...

If the modulation was 94 before the injector service that would suggest the static timing is retarded. Unless the pump timing has been reset i would think your mechanic has damaged the number four injector or set the break pressure to high or to low. The electrical side of the injector is not serviceable. Having the injectors correctly serviced should not effect modulation unduly.
 
Why is the idle RPM playing up?
I removed the injectors and gave them to the service guys. I specifically told them not to mess up with the injector with the wire. They assured that nothing to worry.
I want to check the resistance on 4th injector. What is the expected resistance?
What exactly are the symptoms for break pressure high/low setting?
 
kapilamuni said:
Why is the idle RPM playing up?
I removed the injectors and gave them to the service guys. I specifically told them not to mess up with the injector with the wire. They assured that nothing to worry.
I want to check the resistance on 4th injector. What is the expected resistance?
What exactly are the symptoms for break pressure high/low setting?
Click to expand...

At the point of injection when the pressure of fuel forces it's way past the nozzle pin for injection, the nozzle pin lifts and a pin connected to it is moved in a coil with about 5 volts running through it, the change in resistance causes the voltage to change. This change in voltage is used by the ECU as the point of injection. The ECU uses this signal in conjunction with readings from the crank position sensor to modulate the timing device to place the point of injection at TDC. If the modulation BEFORE the injectors were serviced was 94% that would indicate the static timing of the injection pump was retarded. So a large modulation was needed to correct the retarded static. In your case at idle warm engine 94%. Should be 45% to 55%, ideally be 50%. If the injection pump timing has not been changed, and all was reasonably normal, the only reason your modulation has now dropped can be that there is something wrong with number four injector. Diesel engines rely on a specific amount of fuel to be injected to maintain a specific RPM. If any of the injectors are cracking early or late that would change the power generated by each cylinder. That would cause the engine to hunt. As the ECU tries to adjust fuel to maintain a steady idle. But i can't believe your man has got it that wrong. You need someone who knows what they are doing to look at it. Get the static set properly and look at number four injector. I don't know what the coil resistance is but there must be one and not just continuity or no circuit at all. If the check light is on there has to be a fault shown on Nanocom.
 
Last edited:
wammers said:
At the point of injection when the pressure of fuel forces it's way past the nozzle pin for injection, the nozzle pin lifts and a pin connected to it is moved in a coil with about 5 volts running through it, the change in resistance causes the voltage to change. This change in voltage is used by the ECU as the point of injection. The ECU uses this signal in conjunction with readings from the crank position sensor to modulate the timing device to place the point of injection at TDC. If the modulation BEFORE the injectors were serviced was 94% that would indicate the static timing of the injection pump was retarded. So a large modulation was needed to correct the retarded static. In your case at idle warm engine 94%. Should be 45% to 55%, ideally be 50%. If the injection pump timing has not been changed, and all was reasonably normal, the only reason your modulation has now dropped can be that there is something wrong with number four injector. Diesel engines rely on a specific amount of fuel to be injected to maintain a specific RPM. If any of the injectors are cracking early or late that would change the power generated by each cylinder. That would cause the engine to hunt. As the ECU tries to adjust fuel to maintain a steady idle. But i can't believe your man has got it that wrong. You need someone who knows what they are doing to look at it. Get the static set properly and look at number four injector. I don't know what the coil resistance is but there must be one and not just continuity or no circuit at all. If the check light is on there has to be a fault shown on Nanocom.
Click to expand...
Get your bags packed and find your passport Tony.:D
 
kapilamuni said:
The T/modulation is between 46.1 to 63.3, most of the time around 61.(idling with hot engine).
Before the injector service, T/modulation was around 94, always.

Check engine light remains ON. The idling RPM is at 750 but if I press the accelerator it goes up and settles down at 1230 and thereafter fluctuates within 900 and 1200 in a shaky manner. It can only revert to 750 with shifting gear to D or R. Then it remains at 750 even if I shift to N or P. This happens most of the time if I press the accelerator.
This "non return to idling RPM" is felt even while driving too. When I slow down for traffic , the fluctuation is heard from the engine, bit annoying sometimes.
I could not check the resistance on the 4th injector yet. but confirm wiring in good shape.
Click to expand...

Can you take a trace using the Nanocom of each of the EDC modules. Say 3 minutes of each with a warm engine idling. Zip the CSV files and post them up.
 
Thanks Wammers for the explanation. As the symptom is shaky slowness in coming down from 1250 to 750RPM, I thought it's the inj pump electronics dancing.
Nanocom shows the initial fault again, -"NEEDLE LIFT SENSOR INVALID VALUE ".
Knowing that 4th injector could play up, I did not want to service it but the service guy was so confident, I was
pushed to take the chance.
Will revert with the resistance of 4th injector coil. Hate to remove/replace that manifold.
As Grrrr suggested will get the traces too.
 
kapilamuni said:
Thanks Wammers for the explanation. As the symptom is shaky slowness in coming down from 1250 to 750RPM, I thought it's the inj pump electronics dancing.
Nanocom shows the initial fault again, -"NEEDLE LIFT SENSOR INVALID VALUE ".
Knowing that 4th injector could play up, I did not want to service it but the service guy was so confident, I was
pushed to take the chance.
Will revert with the resistance of 4th injector coil. Hate to remove/replace that manifold.
As Grrrr suggested will get the traces too.
Click to expand...

Fit a new number four injector check modulation and set static as needed. With 94% modulation you should have been getting "Needle lift sensor out of range". or " Modulation out of range". That is static timing retarded NOT a fault with number four injector.
 
Last edited:
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