I originally posted in December 2019 regarding an issue with my father-in-laws camper van having a suspected issue with the cam position sensor on a Lucas Epic injector pump. Anyhow, as I could not repair here in Portugal he drove back to the UK in limp mode, with a clear fault diagnosis to attempt to repair in the UK. 9 months on and lo and behold he has driven all the way back to Portugal in his van, with it still in limp mode (go figure). I have been looking for a Bosch pump to replace the Lucas Epic, but so far no luck here in Portugal (I can get in the UK and ship if necessary). While waiting, I thought f..k it, I'm going to remove the sensor and have a go at fixing the sensor. After carefully and patiently removing all the epoxy then disassembling the internal circuit board and wiring, I have actually managed to repair the sensor, clear the fault and the van is actually running.
Initially there was a virtual short circuit across the terminals of the cam sensor. As I desoldered and slowly lifted the circuit board and wiring out of the housing and while monitoring the resistance across the cam position sensor, the short circuit has vanished and the reading increased to 58 ohm. On further visual inspection, it was seen that the connecting wires have damage to the insulation. I am unsure if this has been done during the disassembly process or if this may have been the cause of the fault. It could have simply been moisture or other contamination creating the issue. I have visually inspected the sensor assembly, heat tested and can find no other issue with what is a small connection pcb, a wound coil assembly for the cam sensor and a small thermistor for the temperature sensor. These are held in place with 2 x M2.5 screws inside the metal housing and then sealed with epoxy. There is a small 'O' ring on the coil former to prevent ingress of diesel. This was duly replaced with a new seal to ensure the integrity was maintained
Unfortunately during the disassembly I have damaged the very thin wires on the temperature sensor. After a bit of further follow up, I have managed to calculate the range of the thermistor and its resistance values at two temperatures and procured a replacement thermistor at a cost of Euro 3.38.
I have made good all the repairs, heat tested and re-installed the unit successfully. I have opted to not epoxy the sensor so that I can easily check in the event of any further issue. I have manufactured a small cover with a gasket and fixed the cover to the assembly using 2 x M2.5 screws and appropriately sized nylon spacers. The total cost for parts was Euro 6.34 from the excellent company Farnell who posted from the UK to Portugal, arriving in less than 48 hours from when the order was placed.
If anyone is curious to what the internals of this sensor assembly are, see attached photos. Its basically a number of coils wound on a former, a thermistor and small circuit board to connect the coil and thermistor to the wires.
I may replace the Lucas Epic pump with Bosch pump in the future, but at least in the meantime the vehicle is running as it should and importantly the in-laws are happy
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Thanks for all the assistance from the members on this excellent forum as without the information available I may never have identified the fault actually being the cam position sensor.
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