Guided test for a common rail diesel piezo injector circuit current. The purpose of the test is to check the current characteristics in the injector control circuit.
Great video.. 👍 If a injector connection is mistakenly pulled out while the engine is running, will the shorting of injector terminals before reconnecting will help solve the unforeseen problems.
great video,I just ran captures on 06 Cummins magnetic type injector that was stuck open.voltages on command and supply wires didn't look any different than a known good injector next to it,then I amp ramp with 2 clamps and both injectors looked the same.i couldn't see the pintle hump on neither waveforn.Can u do an amp ramp capture on magnetic type injector?and volt capture on fuel pressure sensor sync with an injector to diagnose a high return injector flow.ive never seen that test anywhere.
Hello Francisco, thank you for the feedback. You most certainly can carry out this same test with magnetic type injectors using both current clamps and voltage probes (Current being the preferred method) The following Guided Test will help with connection if you wish to measure voltage and current simultaneously www.picoauto.com/library/automotive-guided-tests/vag-pd-current-voltage-and-earth/ Should your injector fail mechanically it may well still exhibit normal voltage and current values! The pintle hump you refer too is typically visible with conventional 12 V petrol “port” injectors as the movement of the pintle influences the magnetic field about the injector windings. However this movement is not so influential with diesel “solenoid” injectors based on their construction and operation. Your idea to measure current flow in a solenoid diesel injector whilst monitoring fuel rail pressure is perfect. Use injector for cylinder 1 as your synchronization signal and AC couple the fuel rail pressure sensor signal to link pulsations in the fuel rail to injection events. This test is what you are alluding to but uses a pressure transducer in the fuel return line. www.picoauto.com/library/automotive-guided-tests/common-rail-diesel-injector-back-leakage-testing/ I hope this helps, take care…..Steve
I dont get this. is common rail bosch injectors correct to read out with just looking at the amp like your test. or the voltage up to 100v.. I have tried voltage reading and when cranking i get all injectors reading peaking at the same time.. voltage around 15v.
Hi Tarik, yes current measurement is a standard way of testing an actuator (i.e. injectors of any type, motors, solenoids etc.) circuit. It tells you what the circuit is doing whereas voltage tells you what the ECU/circuit is asking (loosely speaking!). Also, nowadays, many injectors are driven on both sides of their circuits and you have to look at the net voltage between them to understand how they are being driven (i.e. if the injector has two pins you may see varying voltages on each one, rather than, say, a fixed voltage feed on one side and a switched earth voltage on the other). That might explain what you are seeing. Hope that helps.
Hi, we were using a very old breakout lead that we sacrificed to become part of the permanent test setup on this vehicle. All our latest breakout lead can be found here: www.picoauto.com/products/breakout-leads-boxes You will need to find the correct adapter for your specific application so I can't give you the exact specification that you might need for your test. Barns
For a single injectorit seems as if voltage is being applied multiple times.. why does the amplitude increases & decreases continuously ? Thankyou for the video
Hi. That's a very good question. The current ripple on each event does suggest that the voltage is pulsed to some extent. I'm afraid I can't tell you why they would do that. I guess it could be because the piezo element responds better or needs protection. Or, in fact, it could be that it is caused by the response of the piezo element/circuit to a non-pulsed voltage control signal... I'm sorry that I can't give you an answer. Would be great if anyone else could provide an answer, if they know.
A piezo injector is electrically equivalent to about a 4 micro farad capacitor. The high frequency (PWM) pulses are used to control the charge and discharge currents since the injectors are typically switched to about 140 volts from a low impedance source. Some systems use a small amount of series resistance or inductance to limit the rate of rise of the current and dispense with the PWM current limiting.
