Injectors stuck on after priming pulse
I have two 4 cylinder cars which has developed similar symtoms. Both have Volvo 4 cylinder red engines, both run 1.2.31 firmware, Bosch Motorsport waste fire coil, 60-2 VR trigger. One of the cars did it first with 1.2.20 firmware but continued doing it after upgrading to 1.2.31. The problem manifests itself by leaving one or more injectors on when the ignition is turned on.
Car1 will NOT do it when tested on the bench, or when the prime pulse is not used. This has been a successful workaround. It will also NOT do it when the trigger sensor is disconnected, which probably explain why it doesn't do it on the bench. An injector output is used for the fuel pump relay.
Car2 is a Volvo 240.
The problem doesn't occur when the injectors are not connected when the ignition is turned on. But when the injectors are connected during powerup they will get stuck in an on position.
- this is the key... Very clear indication that it's a HW artifact caused by the injector current. It seems very likely that GND5 jumps above 1V (maybe >2V ?) during the priming pulse when injector currents add up.. Make very strong ground (eg. 5 x 1.23mm2 wires connected 12cm from EC36 receptacles), and if necessary, connect grounds inside ECU (and if it's VR sensor, maybe get a dedicated gnd wire for the VR sensor, from a mainboard GND pad, near the LM1815.I don't think that the problem is found there, the 5X1mm2 grounding has worked on cars with five times the GND5 current. But it's simple to make an internal ground connection to be sure. I think that the actual ground point on the chassi is in an unsuitable location, causing the ECU to reset, it's common to see very strange ground potential problems in Volvos.
This car also leaves the fuel pump on forever when the problem occurs. The fuel pump relay is driven by an ignition output on this car. Removing the prime pulse as a workaround is not tested on this car yet.
http://www.vems.hu/files/MembersPage/JorgenKarlsson/Injectorsstuckon/v3.3_u011245-2016.03.13-15.51.49_1.2.31_injectors%20stuck%20on_Volvo%20240_wastefire_VR_Car2.vemscfg The tune is VERY crude as it was switched over to alpha-N minutes before ending the days tuning.
Possible software issue:
Many cars have some kind of noise during initial powerup. Something in the noise profile on these cars cause the firmware to hang during the prime pulse.
- Can someone check if a trigger interrupt can cause problems during the prime pulse?
- good idea, but it cannot. Thanks for confirming this.
Possible hardware issue:
When all the injectors turn off at the same time after the prime pulse they cause an overvoltage spike resulting in a reset. I have obviously made sure that a good flyback connection is made.
How to test this:
- Check if communication is possible when the injectors are stuck. Find a way to allow testing for longer then a few seconds at a time without risking damaged injectors or fuel everywhere.
- Check if it can be recreated with HiZ? injectors.
- Disconnect all injectors while this is happening to see this unlocks the condition (that would be a hardware reset issue).
- This was tested by the owner tonight with unexpected results. When two injectors were disconnected the fuel pump stopped and the two remaining injectors stopped flowing. The unexpected result is that when connecting the injectors again the pump started again. I wonder if it could be as simple as a bad ground connection between the chassi and battery.
- Scope the fuel pump relay output to see if the pulse is interrupted. (This would indicate a hardware reset.)
- Scope the voltage on the flyback/injector power wire to see if voltage spikes are seen.
- Scope the voltage on pin 25 to see if any anomalies are seen there.
- Scope the trigger input during powerup to see the noise profile.
- Scope an injector output to see if the LoZ? injector PWM is running while the injectors are stuck. They did seem to heat up faster then expected. Are they meant to be pulsed during the prime pulse?
Trigger setup - sounds like VR signal noise (=> fuelpump on; might not explain injout though ) I agree and I will measure the noise levels when it happens, but both cars only have pump run-on when the injectors are stuck. As the idle screw on one car came loose I also know that it does not have pump run-on when it stalls.
- please confirm it has primary trigger VR Confirmed
- DC bias voltage of primary trigger ? I don't expect a problem here but I have considered a stronger pullup as a possible workaround if it's a firmware issue.
- when something weird is thought to happen Hard to do that, with the pumps disabled the injectors heat up fairly quickly if they are left on. I don't want to risk damaging the injectors. With the pumps running it's almost impossible to test more then a few seconds at a time because of the large injector flow.
- at least vemscfg