I have run into this problem again! This time with a Volvo 740 1990. And first gen volvo 5 cyl turbo engine.
Standard installation with Twinshield.
During cranking the trigger is so bad that it does not even fire ignition. See trig logs. Coils and inj unplugged
We have tried the following:
- Added ground: No change
- Polarity switch : no change
- Changed sensor: No change.
- Changed to Volvo B230 sensor with custom bracket. 0.5-3mm tested, marginally better trigger.
- Moved supply and ground for ECU to and from battery, to and from engine block: Minor or no change in trigger.
- Changed starter motor : Much better trigger! To the point that the ECU starts so sync sporadically and fires ignition.
Then we noticed that during cranking the trigger is rubbish, but when you let go of the cranking, the 2-3 last revolutions of the engine the signal clears right up and becomes perfect!
So with patients the car does now start, but its pure luck to its syncs up and start. Maybe 1 out of 20 times.
The funny ting is that when its started it runs perfect! No trig error. But the log still look weird on idle.
And also, the problem seems to get worse when the starter motor and/or cables get warm. Low battery and cold starter seems to make it better. (Then it starts more frequently)
Stock Volvo 740 battery location and cables.
On this above, startermotor on and off short intervals, w/o plugs.
All files located here:
Now my questions:
What causes this? How is the starter-motor picked up in the trigger?
What can be done to prevent this?
I tried to pull down the signal with large resistor, no change in signal.
Can some kind of filter be used, like the ones for radio interference?
We are all out of ideas. But one thing is clear, this problem is common, i have encountered it 4 times now, and here is no solution part from changing to GT101 HALL sensor, that solves the problem. But i would like to get this fixed once and for all.
Suggestion from Mattias :
- Get a cheap Rigol digital scope.
- Try to add +5V pull-up to signal. Not pull-down to ground.
- It looks like the zero-crossing of the signal happens more often than it should. I've had this problem on some Volvo 6 cyl 60-2 trigger wheels where an extra trigger event occurs at the missing teeth at cranking speed, causing a trigger error on every revolution of the engine and no-start.
- The voltage increases just above zero and then drops a few tenths of a Volt below zero, and then goes back up again causing another zero-crossing = trigger event. Raising the voltage with a pull-up resistor lifts this voltage oscillation above ground, causing no zero crossing and no more ghost trigger events.
OLD Post, may or may not be relevant
Volvo 245 with new generation twin VVT volvo T5 engine.
VEMS V3.7, twinshield, simens 875cc, volvo 601 coils.
We have experienced extreme trigger problems during cranking.
Change every singel part inc;
VR sensors, 2 different types.
Flywheel, 2 different types, one solid billet one and one OEM from -97 850 turbo.
What ever we do, there is till always trigger error.
Both less primary, and to many primary.
Wont even fire IGN coils.
We even changed startermotor, and that made the triggerlog much better, but not good enough to start.
Tried everyting, dissconnected everyting but VR trigger, still no good trigger. Moved ground to engine. Moved 12v+ supply. Moved the battery from the trunk back to its original place.
Tried all kinds of settings and polaritys.
Standard trigger wheel brand new sensor
The very best we got. Still not good.
We got this with very low battery, and changed startermotor.
Never seen such a wierd trigger
With jumpercables to antother running car, 13.4 volts
Billet wheel, New type trigger sensor.
All files located here:
I have reviewed your triggerlogs, the log with the standard flywheel looked best but seemed to have swapper VR polarity, could you redo this triggerwheel (stock flywheel if possible), with swapped trigger wires 8-10 seconds cranking without INJ and IGN fuse ? I'll review this new logs we'll work from there.
Best regards, Dave
Unfortunately the customer chose to return his unit to me. :(
I tried polarity change of both wheels, but I didn't name all the logs. All logs are with only VR connected. No INJ nor IGN connected.
Same problem, on all configurations, just varying amount of error.