Fluctuating Idle RPM -Diesel P38

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Mark Piercy said:
wouldn't the cps work or just not work?
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There are a few things going on here that are hard to understand. It is either the CPS or the number four injector. Which would you try first? CPS at about £50.00 or a number four injector at £180.00. Think if i recall correctly he has had problems with the injector before after he had it serviced. May not have been set up correctly. But the modulation was off scale at the time due to chains and pump timing. So it is not beyond the bounds of possibility it is contributing to his problems. Or maybe the cause of them. To be fair i don't think he has any mechanic that knows exactly what they are doing.
 
Mark Piercy said:
well, the cheapest! But cps is just a trigger? It does sound like the Injector. It sounds like the injector is sticking or binding?
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Maybe so, let us wait and see. The ECU via the quantity servo controls idle from signals received from CPS when the idle switch is on below 9% on throttle pot. Even with the number four injector disconnected the idle should be steady.
 
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Guys, got the new,genuine CPS and fitted. No change in random fluctuations in RPM at idle.
Then refitted the old one and tried again , no difference. Then, removed the wiring connector on CPS and started.
The moment it started RPM went too high so scary, switched off the engine. Replugged the connector and started then okay. I guess, this shows the CPS is doing its job.
Checked the faults with Nanocom, the usual timing out of range fault is there, nothing else. After deletion it reappears.
Anyway, Im not going to touch that CPS for the difficulty in doing with starter motor removal etc
Also, now I understand why Wammers insisted on having the stop solenoid fitted.
 
kapilamuni said:
Guys, got the new,genuine CPS and fitted. No change in random fluctuations in RPM at idle.
Then refitted the old one and tried again , no difference. Then, removed the wiring connector on CPS and started.
The moment it started RPM went too high so scary, switched off the engine. Replugged the connector and started then okay. I guess, this shows the CPS is doing its job.
Checked the faults with Nanocom, the usual timing out of range fault is there, nothing else. After deletion it reappears.
Anyway, Im not going to touch that CPS for the difficulty in doing with starter motor removal etc
Also, now I understand why Wammers insisted on having the stop solenoid fitted.
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Can only be the number four injector. Don't play with it fit a new one.
 
wammers said:
Maybe so, let us wait and see. The ECU via the quantity servo controls idle from signals received from CPS when the idle switch is on below 9% on throttle pot. Even with the number four injector disconnected the idle should be steady.
Click to expand...
With the above , how can one explain the behavior once the CPS disconnected? I thought, the engine would not start. Apperantly, CPS controls the idle RPM and without that RPM goes to maximum. Confusing as its not a CPS function, as per RAVE.
If the 4th inj faulty, then CEL should come, isnt it?
 
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I've had a No.4 Injector Fault on a different EDC engine (VP44 not VE-EDC but the injector function is effectively the same). Gave wildly varying injection timing signals as the needle was sticking. Remember that the needle lift sensor tells the EDC when No.4 injector fires, not when it's meant to, so if the injector is sticking and therefore not popping consistently each firing cycle, the injection timing calculated by the EDC will vary and thus the modulation in order to attempt to account for this. Replacement with a known good injector, with new nozzle and properly calibrated solved the problem in this situation. However the symptoms were; inability too set dynamic injection timing due to the fluctuation in modulation, and thus sub par running and extra smoke, not fluctuating idle.

If you do the injector, do the rest at the same time cos if one's worn out the others will be the same. Expensive option but it's about all that's left by the sound of it.

Good Luck,

Rich
 
kapilamuni said:
With the above , how can one explain the behavior once the CPS disconnected? I thought, the engine would not start. Apperantly, CPS controls the idle RPM and without that RPM goes to maximum. Confusing as its not a CPS function, as per RAVE.
If the 4th inj faulty, then CEL should come, isnt it?
Click to expand...

If you have a discrepancy in RPM from CPS to number four injector one of them must be faulty, it can now be said with some certainty it is the number four injector at fault.. They should not vary by more than 40 RPM at ANY time. I think you once said you had the injectors serviced. Looking back at what you have i would say the number four injector is either set at a different crack pressure than the other injectors or that the needle lift sensor has been incorrectly set or damaged giving incorrect RPM and crack off readings that the system is trying to correct by increasing modulation but cannot. The timing device ensures that the crack pressure of the number four injector is reached at TDC. There is leakage past the pressure piston and within the injectors as fuel pressure is applied to them. So the ECU will increase fuel to allow for this loss and to maintain engine speed. If the injectors are cracking at different pressures some will be injecting more fuel than others. This will give a lumpy idle. The CPS controls engine RPM at all speeds in conjunction with the throttle potentiometer other than when the pot is below 9% and the idle switch is engaged and the throttle pot is not being used. Then idle RPM is controlled by the ECU which adjusts the idle fuel to maintain idle speed via signals from the CPS. If the number four injector is faulty in an electrical sense, then yes MIL lamp will come on. But if it has been set up incorrectly or the needle sensor is sticking the ECU and system will know nothing about it and the MIL lamp will not come on. With the CPS disconnected providing the number four injector is functioning correctly engine RPM should not rise above around 2500-3000 RPM as far as i am aware as limp should engage. Don't disconnect the CPS is the best advice.
 
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quote"...................With the CPS disconnected providing the number four injector is functioning correctly engine RPM should not rise above around 2500-3000 RPM as far as i am aware as limp should engage..................." unquote.
I did not observe the RPM but it was very high. then I had to shut it down. May be it was around 2500 RPM.
Yes, I agree that if the 4th inj is electrically in good order then the CEL wouldn't show up.
Just after servicing the injectors I had the CEL on but it vanished after running few days. May be that was the beginning of the problem.

Now to buy a 4th injector.
 
What a saga. On the plus side it was the cheap option (CPS) that was wrong first.

By the time you've replaced all these parts it is going to run like a new car!
 
Guys, found a used 4th injector @75 GBP and a new OE one @ 175 GBP , inclusive of shipping.
Before spending any money, can I get the 4th injector serviced again? Hope it could help since the issue is not electrical.
How about running after wiring disconnected from the 4th injector , will there be any other issues except the CEL on?
 
kapilamuni said:
Guys, found a used 4th injector @75 GBP and a new OE one @ 175 GBP , inclusive of shipping.
Before spending any money, can I get the 4th injector serviced again? Hope it could help since the issue is not electrical.
How about running after wiring disconnected from the 4th injector , will there be any other issues except the CEL on?
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Get a new one. Running with it disconnected engine will be in limp mode.
 
Guys , I'm, back.
Got the new 4th injector on Saturday and it happened to be BOSCH made in India.:eek:
Replaced CPS with new genuine part. and with that changed the starter motor solenoid too.
Then, went to remove the 4th injector. It was so tight and cracked the widow socket (27mm).
Even with a 4ft breaker bar it didn't budge.:mad::mad::mad::mad::mad::mad:

Now wait for the new injector socket. Can anyone give me a link to a strong injector socket, please?
 
hey, if the engine will still run at this moment, spray some wd40 or similar when the engine gets warm it'll help.. Or try heating around the injector with a blow lamp, if the injector is buggered it won't matter so much if it gets caught with the flame...its been in there a few years I imagine:eek:..
 
kapilamuni said:
Guys , I'm, back.
Got the new 4th injector on Saturday and it happened to be BOSCH made in India.:eek:
Replaced CPS with new genuine part. and with that changed the starter motor solenoid too.
Then, went to remove the 4th injector. It was so tight and cracked the widow socket (27mm).
Even with a 4ft breaker bar it didn't budge.:mad::mad::mad::mad::mad::mad:

Now wait for the new injector socket. Can anyone give me a link to a strong injector socket, please?
Click to expand...

Injector is only supposed to be torqued to 48 lb ft. Thought you had removed this some time ago for refurb. Are you sure you are turning it the right way?
 
wammers said:
Injector is only supposed to be torqued to 48 lb ft. Thought you had removed this some time ago for refurb. Are you sure you are turning it the right way?
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I thought the local garage jobbies had a go at it and then "refurbed" it after they damaged it, finding a problem that wasn't there before they started tinkering?
 
Grrrrrr said:
I thought the local garage jobbies had a go at it and then "refurbed" it after they damaged it, finding a problem that wasn't there before they started tinkering?
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So much has gone on with this car i have lost track of it. If you ask me the local mechanics don't have a clue what they are doing. This poor lad is suffering because of their lack of knowledge.
 
My guess would be the fire seal may have seen better days, and therefore the injector is jammed in with carbon maybe? Not got any tricks for dealing with the problem unfortunately though. Is it possible that any chemical might be able to be applied around the threads which might wick through by capillary action and break up any carbon?

Good Luck!

Richard
 
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