Object.

To test the accuracy of URO Parts replacement oil pressure senders for the E type Jaguar.

Results.

All 4 sensors measured consistently at 2 known pressures, however all under read, with greater inaccuracy at lower pressures. The inaccuracy was such that it would not preclude the use of the sensors as a safety device in the case of a real loss of oil pressure in the engine.

Materials and methods.

4 URO C15474 senders were purchased from Ebay for US$28 each.

These were tested using a Smiths 0-60 psi dash board oil gauge from a 1967 Series 1.5 E Type. Testing involved pressurising the sender using compressed air to 30 and 57 psi and recording the pressure measured on the Smiths gauge. The air pressure was applied using a regulator valve attached to a 150psi shop compressor. The pressure was verified using a bourdon gauge known to be accurate. It was not possible  to test at pressure below 30 psi due to limitations of the regulator valve.

Power was from a 12V 2A DC plug pack.  Voltage during testing was measured at 13.8V using a voltmeter connected in parallel across the sender.

Results.

Results are collated in Table 1.

All senders under read at both 30 and 57psi of air. The degree of inaccuracy was greater at lower pressures. No sender over read.

Within the constraints of the testing all 4 senders seemed to read in a similar fashion. Average readings were 17.5psi at 30 psi air and 50.75psi at  57psi air respectively.

All 4 senders exhibited consistent measurements across the 2 measured pressures. All four were consistently inaccurate, under reading by an average of 42% at 30psi and 11% at 57psi.

The time to reach a steady reading was noted to be a lot longer than for either (a) an original sender or (b) another aftermarket sender. Once the sender reached pressure there was no fluctuation over a period of one minute.

Discussion.

The point of measuring oil pressure in an E Type engine is to be made aware that oil pressure has dropped to dangerous levels before the engine fails. A sender that falsely reads a pressure higher than the actual oil pressure may fail to do this. All 4 of the senders tested were inaccurate but all under read the pressure. In a situation where there was a real loss of engine oil pressure these senders would tend to alert the driver earlier rather than later.

2 other senders were also tested; both were previously installed in my cars. One sender read low but was consistent with the URO senders (22 and 53 psi) but the other, a recent aftermarket replacement read high, reading 35psi at 30psi air and deflecting the needle to the far right of the gauge at 57psi. This sender could potentially delay alerting to a fall in oil pressure.

I have removed both these senders and have replaced them with the 2 most accurate ORU senders. I will now drive the cars and see what the longevity of the senders is.

Sources of error in the study include the inability to positively calibrate the Smiths gauge and potential unobserved alterations in supply voltage.  

Maintaining a stable and accurate air pressure with the regulator used was difficult. The range of pressure the regulator is designed for is higher than an average 10 to 40psi pressure range expected from an E Type motor.  It was not possible to maintain a stable pressure of 10psi long enough to allow testing at that pressure. In addition the compressor is positioned under my work bench and getting an accurate parallax free view of the gauge was difficult. That said the pressure readings of 30 and 57 psi of air were stable during the testing.