Datatek
Well-Known Member
Wammers could give a more detailed explanation than me, but basically the modulation figure represents the position of the servo in the FIP, 50% is mid point which is where it should be at hot idle (+/-5%)
I'd need to check to refresh my memory but I think it is the comparison between the start of injection based on the crank position sensor and that measured by the needle in the #4 injector. As Data says, when the load is stable such as at idle then it should be about 50%. Measurements always raken on a warm engine at idle.
brianp38dse
Well-Known Member
Sort the cps out with the shim, then you know thats right and can rule that out of the equation.
Datatek
Well-Known Member
Sort the CPS first.
tomcat59alan
Well-Known Member
Well you will have certainly served your apprenticeship by the time its all sorted. Top marks for persistence.
If the CPS was a problem with no signal the engine would be revving over 2000 RPM i have already said that. Modulation is about point of injection adjustment for various injection pump internal pressures. Static is set with engine locked at TDC number one firing. And is set slightly advanced to aid starting. 0.95mm lift new chains 0.90mm lift old chains. When the engine is switched off, when internal fuel pressure in the injection pump bleeds away timing always returns to static setting. At idle warm engine (minimum internal pressure) modulation should be 45% to 55%. Below 50% static is advanced above 50% static is retarded. The ECM receives a signal from number four injector every two revolutions. This tells the ECM the actual point of injection. The ECM then modulates the pressure control to either restrict or increase internal fuel pressure acting on the timing device piston against spring pressure. This causes the timing device cam to rotate changing the point of injection to 1 or 2 degrees BTDC. As internal injection pump pressure increases due to engine RPM to a max of 4.5 bar, more modulation is required to allow more fuel flow away from the timing device piston to adjust point of injection within specified tolerance throughout the rev range. That is why modulation should never be checked at other than idle warm engine.
How are you going to check for correct modulation when you can't get it to idle? You need to find out why idle control is not working. Think you said you fitted a new injection pump hope it's not one somebody has been buggering about with.
Lukas018
Well-Known Member
No sorry just to recap the below is what is happening:
1. Engine starts.
2. It idles but very bad readings on live data between 728 and 750 rpm but fluctuates right down to 628 and smokey.
3. Any load like put in gear at tick over and it stalls but no load rough idles.
4. When starting from cold it doesnt idle higher like should until warm.
3. When at say 1500mm rpm sounds fine no smoke.
4. Live data on 4 runs 2 runs showed idle not active then active on tick over.
5. Lift needle injector 4 comes up as fault and then goes.
Last 2 runs showed no faults but still idling rough.
This is where I am confused on what to do and check?
Hope that makes sense might throw some light.
The pump was removed from another p38 and I saw it running and you remember how many times it took for to time it unless this has been disturbed when tensioner on upper chain may have thrown it out slightly?
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If static was done correctly and locked at TDC fitting upper chain can change nothing. Think you have an electrical problem. But you need to go over everything again to take things out of the equation. Sort CPS, check static. Check wiring to number four injector for damage and connection. If it's running like a bag of bricks and Hawkeye is showing no faults something is rotten in Denmark.
Lukas018
Well-Known Member
Right ok will go over it all.
What's best method to check static timing same as before or RAVE procedure?
Lukas018
Well-Known Member
Ha ha thanks @tomcat59alan it was my dad kept me going was giving up on it ages ago. Need a knighthood after this!!Well you will have certainly served your apprenticeship by the time its all sorted. Top marks for persistence.
RAVE procedure.
Datatek
Well-Known Member
Static timing is the only way if you cannot check the modulation.
Lukas018
Well-Known Member
Checking CPS and Injector Connection then will check pump timing waiting for my dad to come and help me
Datatek
Well-Known Member
You are getting there. I doubt that the static timing would cause a fluctuation of 22rpm. The aircon is switched off I suppose?
Lukas018
Well-Known Member
I removed the compressor and air con rad as they were both bust. Would this affect the weighted balance of the engine having the compressor off?
Sorry forgot to say two faults are now persistent, needle lift sensor, going to get injector checked.
Other fault is engine speed sensor? This wouldn't be the cps would it?
