Focus piece: Sight block
by Pico Technology

The introduction of the Pico Sight Block this January opens up another level of diagnostic capability to the WPS500X. This accessory is extremely useful when you are looking for air in low-pressure diesel systems.

The Sight block is now available from Pico in the Low pressure fuel kit (PQ071). The kit comes with a stop valve for testing a negative pressure fuel pump under load, and 3 sets of hose barbs for connecting to different size fuel hoses.

By using the quick-couple barb connectors supplied with the Sight Block, you can effortlessly connect to the vehicle fuel supply and return lines. With a connection like this, you can monitor the integrity of the fuel priming circuits with regards to aeration, colour and direction of flow.

A typical example can be found in this case study, where multiple Sight Blocks were used to diagnose a VW Caddy with prolonged engine cranking.

Split or wrongly fitted seal rings on filters or worn fuel supply pipes can be a real problem. The sight block forms the classic T-junction, to which we can connect the WPS500X to add pressure analysis to fuel priming and return lines. With the stop valve, the efficiency of fuel pumps, fuel lines, O-ring seals, hoses and pipework can be rapidly evaluated while you monitor the positive/negative pressures with PicoScope for the shut-off period.


The waveform above demonstrates the maximum negative priming pressure achieved from a high-pressure diesel pump with the stop valve closed (transfer pump integrity test).


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