P38A Diesel engine probs

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wammers said:
It sounds like the refurb place do minimal refurbishment using old parts. When refurbing a pump a new quantity servo is a must.
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Obviously I can only say what I've been told but I think they said the pump came refurbed by and/from Bosch, and that the electrical components for these pumps were now no longer produced by Bosch, so I assumed that it had 2nd hand electronics anyway. Is this right do you think ? But at least it has a 12 month warranty and I haven't got do it all again, twice was enough ! :rolleyes:
 
Dieselmech said:
Obviously I can only say what I've been told but I think they said the pump came refurbed by and/from Bosch, and that the electrical components for these pumps were now no longer produced by Bosch, so I assumed that it had 2nd hand electronics anyway. Is this right do you think ? But at least it has a 12 month warranty and I haven't got do it all again, twice was enough ! :rolleyes:
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Bosch will have the means to refurbish the quantity servo. It is a major fail point on high mileage pumps.
 
wammers said:
Bosch will have the means to refurbish the quantity servo. It is a major fail point on high mileage pumps.
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Hi, Update on the situation, the pump was taken off by the diesel shop who supplied the new pump and sent back to the supplier. It was duly sent back the next day and refitted and we still have the same problem with the engine revs dropping suddenly when put in to gear or the aircon compressor clicks in or both. The diesel shop said that they were told it was ok. What to do next?
 
Dieselmech said:
Hi, Update on the situation, the pump was taken off by the diesel shop who supplied the new pump and sent back to the supplier. It was duly sent back the next day and refitted and we still have the same problem with the engine revs dropping suddenly when put in to gear or the aircon compressor clicks in or both. The diesel shop said that they were told it was ok. What to do next?
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I'm guessing, but is it not the EDC that controls the idle up when a load is applied, the EDC certainly controls the set idle speed? If so could it be an electrical connection problem?
 
See the attached. Might be of use?

From memory all the stall is controlled by EDC. However, if modulation is too far out it can only go so far.
 

Attachments

  • Bosch_VE_Pumps.zip
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Grrrrrr said:
So how does it adjust the fuel when it feels like it is stalling?
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Modulation is about timing adjustment NOT fuelling. Number four injector sends a signal to the ECU at the point of injection. This signal is then compared by the ECU to a TDC signal from the CPS. The ECU then modulates the the timing solenoid to adjust the internal fuel pressure being applied to the timing device piston against spring pressure. This moves the timing device to advance or retard the point of injection to within a degree or so before TDC. That has nothing to do with idle control. Modulation is ALWAYS checked with engine up to temp and at idle. Obviously as RPMs rise internal fuel pressure increases so modulation will increase, so if modulation is checked above idle it will be a false reading. When the throttle pedal pot is below 9% idle control comes into operation. The ECU monitors idle speed signals from CPS. If the RPM falls below 750 because of load being applied, the ECU moves the quantity servo to provide more fuel to sustain 750 RPM. If the load is then removed RPM will rise and the ECU will reduce fuel via the quantity servo to lower the RPM to 750. Problems with stalling from idle come when the feedback pot/wiper wear and the wiper loses contact with the pot. If the ECU gets no quantity servo position signal feedback it shuts the engine down by dropping the stop solenoid.
 
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wammers said:
Modulation is about timing adjustment NOT fuelling. Number four injector sends a signal to the ECU at the point of injection. This signal is then compared by the ECU to a TDC signal from the CPS. The ECU then modulates the the timing solenoid to adjust the internal fuel pressure being applied to the timing device piston against spring pressure. This moves the timing device to advance or retard the point of injection to within a degree or so before TDC. That has nothing to do with idle control. Modulation is ALWAYS checked with engine up to temp and at idle. Obviously as RPMs rise internal fuel pressure increases so modulation will increase, so if modulation is checked above idle it will be a false reading. When the throttle pedal pot is below 9% idle control comes into operation. The ECU monitors idle speed signals from CPS. If the RPM falls below 750 because of load being applied, the ECU moves the quantity servo to provide more fuel to sustain 750 RPM. If the load is then removed RPM will rise and the ECU will reduce fuel via the quantity servo to lower the RPM to 750. Problems with stalling from idle come when the feedback pot/wiper wear and the wiper loses contact with the pot. If the ECU gets no quantity servo position signal feedback it shuts the engine down by dropping the stop solenoid.
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That makes sense. Got a feeling you've said this before so apologies for being slow on the uptake. For some reason I thought that if modulation was a long way out then it also moved the quantity server. Probably from it cutting out when modulation very high.
 
wammers said:
Modulation is about timing adjustment NOT fuelling. Number four injector sends a signal to the ECU at the point of injection. This signal is then compared by the ECU to a TDC signal from the CPS. The ECU then modulates the the timing solenoid to adjust the internal fuel pressure being applied to the timing device piston against spring pressure. This moves the timing device to advance or retard the point of injection to within a degree or so before TDC. That has nothing to do with idle control. Modulation is ALWAYS checked with engine up to temp and at idle. Obviously as RPMs rise internal fuel pressure increases so modulation will increase, so if modulation is checked above idle it will be a false reading. When the throttle pedal pot is below 9% idle control comes into operation. The ECU monitors idle speed signals from CPS. If the RPM falls below 750 because of load being applied, the ECU moves the quantity servo to provide more fuel to sustain 750 RPM. If the load is then removed RPM will rise and the ECU will reduce fuel via the quantity servo to lower the RPM to 750. Problems with stalling from idle come when the feedback pot/wiper wear and the wiper loses contact with the pot. If the ECU gets no quantity servo position signal feedback it shuts the engine down by dropping the stop solenoid.
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So I assume from what you are saying that the wiper and pot are in the top housing of the FIP. So you are saying that it is still an electrical problem with the FIP???
 
Dieselmech said:
just to give a final update. It went in for a service and had the faults read whilst running which said intermittent fault with the fuel quantity actuator. The pump was changed for another new one and its now perfect. Thanks for all the help.
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So pump off again for the 3rd or 4th time! And it turns out Wazza and Wammers were spot on right at the start of the thread!
 
Grrrrrr said:
So pump off again for the 3rd or 4th time! And it turns out Wazza and Wammers were spot on right at the start of the thread!
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Yes I did it twice as fault after about 100 miles, and the pump shop did twice, the second time fitting a new pump. It seems to happen all the time, things having to be done more than once, seems to be the norm these days. Brought a non genuine water pump for a Perkins engine in a forklift, there was no way on gods earth it would have fitted. So had to buy a genuine one. Which wasted 2 days!! Why sell a part that won’t fit it will only end up being returned and give you a tarnished name ffs
 
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