High fuel consumption. Update.

[goldfinche]

Hello a little time back I asked about fuel consumption on my 2-1 td, it was not good and still isnt.. I read that one of the injectors has a wire coming from it and if it is disconnected then the engine would run rough etc. so I disconnected it and the result was that it made not a bit of difference, the engine management light does not light when it's disconnected and has anyone got any idea whats happening. Injector ? Pump ? ECU ?
To recap fuel round town 30 mpg maximum, on a run (motorway) 38/40 mpg @ 60/65 mph. Being gentle with the throttle. From 3000 rpm up then large amounts of throttle will cause black smoke until the engine 'catches' up with the throttle. New air filter and exhaust.
Puzzled .
Cheers.
Geoff.

[AndersDK]

The injector with a wire has a coil sensor build in to sense the injection needle moves. This gives a magnetic induction signal in the coil sensor.
This signal is used by the ECU to determine - and hence correct - the injection timing.

It says then that if the sensor is not working, you wont get an optimised injection, and in turn fuel consumption suffers.

The sensor must have a connector pair ?
Dislodge the connector and do an ohms check out to the sensor. Should be something sensible for a coil, like some 100-600 ohms. Not shortcircuited and not disrupted of course.
If it is disrupted, you will need the complete injector, as the coil sensor does not come separately.

[goldfinche]

Thank you Anders that makes sense , I would have exspected the engine management light to give a warning that something was wrong but it dosnt. I will check the sensor tomorrow. Any idea what the waveform should look like I do have a silly scope and long ext lead.
I will come back and let you know.
Cheers.
Geoff.

[goldfinche]

Hello have measured the injector resistance and it is 102 ohms. Will see if anyone comes up with anything. If I can find another injector to measure then that may be interesting.
Cheers.
Geoff.

[AndersDK]

The waveform must be a simple AC peak.
As it comes with the rpm frequency it can be heard to view anything at higher scantime frequencies.
But then it would mostly look like a single welldamped coil shot.

No idea on the Vptp value, but my guess some 5V.

[CitroJim]

Yes, 100 ohms is about right Geoff. The waveform I would expect to be a fairly "dirty" pulse train, a low pulsewidth at idle and increasing in frequency and pulsewidth as the engine speed and load increases.

I'm surprised the K light has not come on if the sensor is not working as it's job is important. It detects the start of injection as the injector needle lifts off the seat and the ECU compares this with the TDC sensor signal to confirm the actual timing value it thinks it has set on the pump for the given rpm and engine load. It needs to do this because the pump timing is controlled by a servo. In electronic terms it works like a phase locked loop (PLL) or a closed-loop in petrol fuel injection terms.

If the lift signal is absent, the ECU should switch into "limp home" and set the timing somewhat retarded. That would explain the poor fuel economy and smoke you see.

[goldfinche]

Hi all. From all I can see the injector is OK but there is something wrong somewhere. There is no difference in the running with the injector disconnected. It starts the same, it drives the same, from what I can estimate the fuel consumption is about the same, 305 miles to a tank full!!!
The 'k' light does not come on with the engine running.It does the self check and flickers when the code is put in from the code pad.
Hi Jim you say that the pump has a servo for the timing, I dont know anything about this pump would it be possible that this has seized ???
I will try to get the codes read but that could take some time, but as the 'k' light does not show anything then it probably wont. As it's going to be up for sale very soon then I would like to sort it. Unless someone would take it as is.
Cheers.
Geoff.

PS
If its the ECU then I am in trouble. Just had a thought, usually it takes about 3/4 seconds for the first cold start of the day but twice it has started instantly as it should. Compared with a 2-1 XM I had, it is gutless, the XM would push you in the back at 90 mph if you gave it some throttle, but it did have a Bosch pump.

[CitroJim]

Hi Geoff,

Certainly, on the 1.9TD, disconnecting the lift sensor causes a very significant change in the engine note and brings on the K light. If there is no difference at all with yours either connected or disconnected then there is a problem. It may be a little different on a 2.1TD with a Lucas EPIC but logically, I would not have thought so.

Have you had a 'scope on it to see what it is doing? I'd be very inclined to say the injector was duff even though statically it looks OK and injects fuel OK.

It is very unlikely the timing servo is seized in the pump. It is bathed in diesel and only a catastrophic mechanical failure could cause it not to operate. A good test will be to disconnect the TDC sensor and see what effect that has. That should provoke the K light to come on and make the ECU enter "limp-home" mode as well as make the engine run rather roughly through the timing reverting to a default retarded setting.

A seemingly random question but is your tacho working normally?

[goldfinche]

Thanks Jim I will try and disconnect the TDC and see what happens.
Cheers.
Geoff.