P38A Nanocom Readings

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ovalandrover

ovalandrover

Well-Known Member
Posts
1,610
I have the modulation reading of 17.6% at idle but when it reaches about 2000 rpm it jumps to 68%. The injector set point is 1.6deg and the actual injector is 10.9 which is not correct as it should be within 1/2 deg
I have set the timing up manually to .95mm at TDC and this is a pump that has just been overhauled.
The car starts up on the button and no smoke. this is after the timing chain has been corrected as from my previous post where the timing was out and also the guide was not fitted properly.
can anyone tell me how the injector set point id determined? and i also assume that the actual is set up manually by the dial gauge .
as its raining at the moment so im not going to get wet but will try adjusting the timing tomorrow to get it within limits.
but would like to know how the injector set point is determined
 
ovalandrover said:
I have the modulation reading of 17.6% at idle but when it reaches about 2000 rpm it jumps to 68%. The injector set point is 1.6deg and the actual injector is 10.9 which is not correct as it should be within 1/2 deg
I have set the timing up manually to .95mm at TDC and this is a pump that has just been overhauled.
The car starts up on the button and no smoke. this is after the timing chain has been corrected as from my previous post where the timing was out and also the guide was not fitted properly.
can anyone tell me how the injector set point id determined? and i also assume that the actual is set up manually by the dial gauge .
as its raining at the moment so im not going to get wet but will try adjusting the timing tomorrow to get it within limits.
but would like to know how the injector set point is determined
Click to expand...
If the modulation at idle with the engine hot is 17.6%, I'm sorry but the static timing is incorrect.
 
RangeRoller dt said:
Injection set point comes from no4 injector sensor to ECU.
ECU uses this and TDC from cpcs/flywheel pins to modulate timing solenoid.

Is your modulation high or low I’d look at on diagnostics if it’s not already apart.
Click to expand...
as u see from my post the modulation is low untill it reaches 2000rpm then goes high
 
Datatek said:
If the modulation at idle with the engine hot is 17.6%, I'm sorry but the static timing is incorrect.
Click to expand...
as i say ill try and set it up with the nanocom but im still worried about the set point and actual
and also the engine light comes on
 
I have had a fault that says timing is out of expected rsnge but cleared that and hasnt come back
 
ovalandrover said:
I have had a fault that says timing is out of expected rsnge but cleared that and hasnt come back
Click to expand...
The timing needs doing properly.
As for the other things, see what you get when the timing is correct.
Worth checking the wire to the needle lift sensor, it's not unknown for it to get trapped if the manifold has been off.
 
Datatek said:
Worth checking the wire to the needle lift sensor, it's not unknown for it to get trapped if the manifold has been off.
Click to expand...


The no 4 injector is new and the wires are not trapped and also the ecu has been changed with exatly the same results and also the MAP & MAF heave been changed for known good ones

i have a wiring loom i can try and the crank sensor has been tried with a known good one and the throttle pot checks out ok with nanocom and the becm heat sensor has been replaced
 
ovalandrover said:
The no 4 injector is new and the wires are not trapped and also the ecu has been changed with exatly the same results and also the MAP & MAF heave been changed for known good ones

i have a wiring loom i can try and the crank sensor has been tried with a known good one and the throttle pot checks out ok with nanocom and the becm heat sensor has been replaced
Click to expand...
As far as I'm concerned you are flogging a dead horse until the static timing is correct, you can change everything and it will make no difference to a mechanical timing error.
BECM heat sensor? WTF is that???
 
ovalandrover said:
I have the modulation reading of 17.6% at idle but when it reaches about 2000 rpm it jumps to 68%. The injector set point is 1.6deg and the actual injector is 10.9 which is not correct as it should be within 1/2 deg
I have set the timing up manually to .95mm at TDC and this is a pump that has just been overhauled.
The car starts up on the button and no smoke. this is after the timing chain has been corrected as from my previous post where the timing was out and also the guide was not fitted properly.
can anyone tell me how the injector set point id determined? and i also assume that the actual is set up manually by the dial gauge .
as its raining at the moment so im not going to get wet but will try adjusting the timing tomorrow to get it within limits.
but would like to know how the injector set point is determined
Click to expand...

I'm no expert at this and I'm sure @wammers will correct me but I think the setpoint injector degrees is when the fuel should have gone into the engine based on the crankshaft sensor. Because there's a lag between when the fuel was supposed to go in and when it actually did go in you get the actual degrees figure which I think is from injector #4, the percentage difference being the modulation.

I can never remember which way round it is but chain-stretch makes modulation percentage go up so presumably that is injection happening later than intended? Which means lower modulation must be happening earlier. If modulation tried to go either below 0 degress or above 100 then it logs a fault and won't run properly as it is outside any known value on the map - presumably it drops back to a default value at that stage.

As you accelerate or decelerate the modulation will change as the car is constantly trying to catch up with the previous value. I think held steady at a certain load it should settle down, although all tests are usually done at warm idle (as you I'm sure you already know!)

17% sounds very low. If my assumption is correct that means the fuel is going in sooner than expected. I guess chain isn't set right. Or too much pump pressure might cause that? Beyond my ken so just guessing.
 
Datatek said:
As far as I'm concerned you are flogging a dead horse until the static timing is correct, you can change everything and it will make no difference to a mechanical timing error.
Click to expand...

The engine starts first hit and there is no smoke. when the revs hit 2000the modulation jump 50 % and the throttle held steady the engine will rev to 3500 thendrop back to 2500 and then go to 3500 again and drop back with no input on the throttle pedal and the MIL light will be on untill the foot ilifted and then dropback to idle idle speed is 748 steady no matter what the load a new no 4 injector has been fitted, and the static timig was set up with the front cover off and the engine at tdc and timing marks and bright links lined up and cam plate in place.
modulation is steady but at 68%
 
ovalandrover said:
The engine starts first hit and there is no smoke. when the revs hit 2000the modulation jump 50 % and the throttle held steady the engine will rev to 3500 thendrop back to 2500 and then go to 3500 again and drop back with no input on the throttle pedal and the MIL light will be on untill the foot ilifted and then dropback to idle idle speed is 748 steady no matter what the load a new no 4 injector has been fitted, and the static timig was set up with the front cover off and the engine at tdc and timing marks and bright links lined up and cam plate in place.
modulation is steady but at 68%
Click to expand...

Modulation is only ever checked at idle with engine up to temp. The modulation has to rise as engine is revved because internal pressure in pump increases with RPM so modulation has to increase to dump more fuel pressure from timing device piston and maintain point of injection at TDC. With static timing set correctly modulation should be between 45% and 55%, ideally 50% at idle engine up to temp. Anything below 50% and the static is advanced anything over 50% the static is retarded. Mid range modulation at idle engine up to temp gives scope for the timing device to move in either direction to adjust the point of injection. Static timing is set slightly advanced to aid starting. When the engine is stopped and internal pressure bleeds from injection pump, static always returns to this setting under spring pressure. When the engine starts an actual point of injection signal is sent from number four injector to ECM, ECM then compares this signal to TDC signal from the CPS. Timing device solenoid is then modulated to bring actual point of injection inline with TDC signal from CPS. CPS signal (injection set point) and (actual point of injection) number four injector signal, should at idle with modulation in range be within 1 or 2 degrees. If the engine is behaving as above i suggest you look at CPS. But if you remove it to check, DO NOT remove the bracket it is attached to ONLY remove the CPS from the bracket. If the bracket is removed a special tool is required to reset CPS air gap.
 
Last edited:
wammers said:
. If the engine is behaving as above i suggest you look at CPS. But if you remove it to check, DO NOT remove the bracket it is attached to ONLY remove the CPS from the bracket. If the bracket is removed a special tool is required to reset CPS air gap.
Click to expand...

The CPS has been replaced with one that is working correctly on my other car and the one taken off is in my other car working ok
 
ovalandrover said:
The CPS has been replaced with one that is working correctly on my other car and the one taken off is in my other car working ok
Click to expand...

Get the static correct then and see what you get. But sounds to me like ECM is losing contact with CPS. And taking RPM readings from number four injector.
 
Last edited:
If you have fitted new chains and set static to .95 the modulation at idle engine up to temp will be less than the lower figure of 45% quoted. If you used old chains static should have been set to .90 and the cam timing should have been set with a 4.61 mm shim under the manifold side of head. And the modulation should be within the range quoted.
 
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