Injectors not firing

[PITA_Z]

Hi, I've just come from doing a bunch of testing trying to determine why my injectors aren't firing.

IIRC, there were PW & duty cycle readings in TunerStudio while attempting to start the car, yet no actual injecting.

 

 

 

The injectors are low-impedance (used dropping resistors stock)

I have the PWM stuff installed, but I'm not using it, so my settings were:

 

Injector Open Time: 1.2ms

Battery Voltage Correction: 0.1

PWM Current Limit: 100%

PWM Time Threshold: 25.4ms (edited wrong value)

Injector PWM Period: 40us

 

The unit is an MS2 v3.0 with 3.1.0 extra code.

 

 

I had taken the MS out of the car a while ago, and at the time I tested with an oscilloscope to see if there was actually

a signal to the injectors to fire, but there was nothing at all.

 

Recently, I had my uncle help testing through the MS unit itself, back through into the MS2 CPU and we found,

while using Injector test mode, that the output waveform looked correct inside the MS but the signal was too

weak (0.15V?) to actually turn on the driver.

He said though that the unit seemed fine, but the problem was possibly a code problem.

 

I just reloaded the 3.1.0 firmware onto the board and opened TunerStudio and left it running.

The water temp & injector pulse width suddenly changed (didn't happen during the testing previously).

They would normally sit at 82*C & 0.0ms, but then temp would jump to like -21 & PW to around 0.160

I don't know if that was merely just a result of having no sensors connected, or a problem after reloading the firmware.

 

Any suggestions on what to check/do next?

 

 

Thanks.

Edited June 7, 2011 by PITA_Z

[s30red240z]

try with out resistors this settings on V3.0

 

* PWM Time Threshold to 1.0 msec, and

* PWM Current Limit to 30%

[PITA_Z]

We did try using those values while testing and still no output at the DB37 pins.

[rsicard]

We did try using those values while testing and still no output at the DB37 pins.

 

Need to determine why there is no Pulse output on the injector lines. Put 15 ohm loads on each injector output and I think the other side of the resistor goes to +14 volts supply. Then check with Oscilloscope for pulse outputs on the injector lines from the ECU.

 

Don't understand why using the low impedance injectors??? Adding resistors make NO SENSE at all with LOW IMPEDANCE injectors. That just lessens the current to the injectors. I am puzzled and have 38+ years in electronics and a background in EFI.

[rsicard]

Looked at the Megasquirt schematic. There is a LED hooked up to the Micro Processor that indicates pulses out for Injector drivers but this is WAY UPSTREAM from the injector drivers. If this LED is pulsing on and off then use the Oscope to trace pulse signals from the Micro Processor to the injector drivers. If all is well there, double check the wiring to the injectors.

[PITA_Z]

We were bench testing out of the car. Also I'm assuming Low Impedance is the term, but whatever is the type that uses the resistors, as I said, it used the dropping resistors as stock.

We used a 12V power supply to power the MS and to resistors we placed on the DB37 injector output pins since we didn't have Injectors to hook up (wasn't at home), and didn't see anything. Also last night, I tested again as I pulled & used one of the injectors off the car and used one of my dropping resistors (ARCOL 3.3ohm 50W - one for each bank) , still same result, nothing.

 

We followed the schematics here:

http://www.msextra.com/doc/general/ms2v3schems.html

Tested with O-scope & logic probe back to the CPU from the injector drivers and according to my uncle (This stuff was getting way over my head) the CPU (JP2) was sending a

low rather than a high signal for one of the two signals required, from the CPU to the NAND IC (U2), and that was why he assumed it could be corrupt code or something.