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Measurement of cable harness to injectors

Did some measurement of the cable harness and the ECU to recoqnize possible sources of the fault.

Injectors and idle-air output measurements

Measure injector and idle air pins against AANpin37 (that is the flyback pin, same function as EC36pin23 in standard VEMS docs)

** inj cyl1, AANpin17, EC36-pin20, INJ-D -> 12.0 Ohm

** inj cyl2, AANpin16, EC36-pin8, INJ-C -> 12.1 Ohm

** inj cyl3, AANpin36, EC36-pin9, INJ-E -> 12.0 Ohm

** inj cyl4, AANpin35, EC36-pin19, INJ-B -> 11.9 Ohm

** inj cyl5, AANpin34, EC36-pin7, INJ-A -> 11.9 Ohm

By measuring directly on the injectors I got values between 11.9-12.0 Ohm.

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Grounds

Measure that grounds are strongly (max 0.1 Ohm) connected inside the VEMS ECU.

Harness:

** AANpin10 to AANpin19 -> 0.5 Ohm

** AANpin19 to AANpin24 -> 0.6 Ohm

** AANpin24 to AANpin10 -> 0.5 Ohm

** AANpin30 sensor ground -> -

** AANpin48 trigger ground -> -

ECU:

** AANpin10 to AANpin19 -> 0.3 Ohm

** AANpin19 to AANpin24 -> 0.3 Ohm

** AANpin24 to AANpin10 -> 0.3 Ohm

** AANpin30 to AANpin48 -> 0.3 Ohm

Measure ECU pins: verify that all the above grounds are connected inside the ECU.

Measure that first 3 are connected in the harness. AANpin30 (sensor ground) and AANpin48 trigger ground are likely not connected inside the harness.

I used a cheap DVM with a measurement range of 0-200 Ohm, is 0.3 Ohm a to high value on the grounds inside the ECU?

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Internal flyback testing

Found the information about this test here http://megasquirtavr.sourceforge.net/manual/Detailed.Output.Flyback.html

The first test must be performed to ensure that the internal flyback connection is in place and working.

** Make sure the Genboard module is powered off.

** Disconnect the first injector.

** Connect DVM negative/common to injector connector common pin (the wire that runs to EC36-pin23).

** Connect DVM positive to the other injector connector pin.

** Measure voltage drop with DVM (in diode mode).

The measured voltage drop should be approximatly 600-1500mV. Repeat the test for the other injectors.

** injector1 -> 1661 mV

** injector2 -> 1698 mV

** injector3 -> 1698 mV

** injector4 -> 1698 mV

** injector5 -> 1698 mV

When I swapped and measured with DVM positive to the injector common pin and DVM negative to the other injector pin I got these values.

** injector1 -> 1193 mV

** injector2 -> 0 mV

** injector3 -> 0 mV

** injector4 -> 0 mV

** injector5 -> 0 mV

I assume this value should be 0 mV for all injectors. Is the flyback for injector1 inside the ECU broken?

Is 1698 mV a to high value on the other flybacks or is it in the range of what you can expect to get from a new flyback?

G: I think this method is usable if TVS 30V flyback diode is locate outside ECU in the harness attached to EC36 pin23. Are it? If flyback diode is in the ECU, measurements must be infinity in any DVM polarity. Then this measurment must be taken between "flyback pad" inside ecu and injector chanels. Now you must check where is this diode and wiring to pin23. Injector 1 channel have some damage anyway. Shorted inside ecu or fried FET. FET usualy cause fried resistor at gate pin too. Damage of this kind can be two reasons: output shorten to positive or no/open flyback circuit. Probably second. MembersPage/GintsK