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start of injection sensor on a P38


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Hi Lads and lasses could someone confirm for me that the start of injection sensor is or is not inside the fuel pump on my 00 P38. I've a second hand pump lined up for 100 I just need to be sure the sensor is actually internal before I go about stripping. I'll buy the pump anyway but if I can replace the sensor without ripping out the pump I'll be a happy camper. Tia.

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My advice is always NOT to start work on these vehicles without reading the relevant manual.

By extension, you should have one on your own PC, so you are independent of an internet connection.

The following extract from the Workshop Manual applies whether or not the engine is fitted with EGR.

Start of injection sensor

The start of fuel injection is registered by this sensor which is incorporated in No 4 injector.

The sensor consists of a coil which surrounds the shaft of an extended injection needle.

The coil is fed a DC supply from the ECM which produces a magnetic field.

When the needle is moved under the influence of fuel pressure, the magnetic field is disturbed which induces an AC voltage in the coil.

The induced voltage is registered in the ECM as a reference point for the start of injection.

The ECM uses the input signals from the start of injection sensor, together with signals from the crankshaft position sensor, to detect the actual start of injection angle.

The detected actual value is adjusted by the ECM to a nominal value via the injection timing solenoid.

I do not know what led you to think the Start Of Injection sensor was faulty, or why you thought it was in the pump.

However, the following extracts from the Workshop Manual may indicate where some confusion has occurred.

Injection timing (Start of Injection) control

The start of injection is controlled by the injection timing device in the injection pump.

A solenoid valve modulates the internal pump pressure on one side of the system so that a defined start of injection is set.

When no power is applied, the solenoid valve is closed, resulting in advanced injection timing (start of injection).

Some overall guidance.


If a fault occurs in any of the following circuits:

manifold absolute pressure sensor, fuel temperature sensor or coolant temperature sensor, the ECM will provide substitute values.

In the case of a faulty throttle position sensor, start of injection sensor or injection timing device, the engine will run at a reduced performance level.

If the servo unit potentiometer or servo unit fails, the injection system is deactivated. The engine shuts down as a result.


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Hi David and thanks for the prompt reply. I had the jeep diagnosed as having the start of injection sensor gone. From your reply I can see that I have been wrongly informed of the location of the sensor. I downloaded rave to my pc and on the same night picked up a virus. I haven't got round to wiping the laptop yet so I'm held to getting on here for education for which I am greatful. Can you please tell me if I can get the injector with the added senor or can I get the sensor separate and just change it out? As always Tia.

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When you are spending this money, check again that you are as certain as you can be that you are buying the most likely part.

It will help if you update your profile to give us a clue where you are in the world.

I believe the sensor is an integral part of the injector.

I do not know of any means of testing it for viability, but there may be some way of testing the coil output, perhaps on an oscilloscope.

I used TT Automotive in Loughborough, UK to find the part number of the injector 'fitted with needle movement sensor', the Bosch part number is given as 0432217236.

Note that the TT prices include UK VAT, so treat their £210 as a target price (In the long distant past I found TT to be helpful and price competitive, I haven't needed to use them for at least 5 years).

There may be a variation on model year, make sure you know what yours is, or have the engine number to hand if dealing with a Diesel specialist like TT.

I also searched eBay.co.uk for that part number you will see the TT price is in the UK ball park. Some of the International suppliers quote keener prices.


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On Testbook,(LR diagnostic tool) you can watch the output of the needle lift sensor in #4 injector as live data,it is shown as an rpm value,which should match the crank sensor value,unless the engine is on overrun when there will be no injection.

The output from the needle lift sensor viewed as an oscilliscope trace will be a fuzzy mess,believe me I've done it.

My suggestion is to very carefully check the wiring from it all the way back to the ecu,that engine is a vibratory old lump and will wreck wiring,the sensors are very reliable in general.

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