HELP! - no start, was running before

[jycheung]

Hi there,

Would appreciate your help regarding a no start condition.

During the last race weekend on the first day the car ran great.  The last race was a 40 minute mini enduro, but otherwise started, ran and was good when I turned off the engine.  I let the car sit outside overnight (mildly cold, around 10 degrees outside).  Day 2 of the race weekend the car would crank but not start so I was done for the weekend.

Here are the details

Standalone Link G4+ storm

Crank trigger - reluctor - 12 even space

Cam trigger - reluctor cam pulse x 1

Direct spark with coil packs

Direct fuel injection

I tested injector outputs, they work.  I tested ignition outputs, the spark plugs fire.  I tested triggers 1,2 - no errors on runtime values.

My external oscilloscope on the triggers, the max voltage on cranking for trigger 1 - 0.18V ish.  Trigger 2 is greater than 1 volts.

The link ecu scope tracing does not look good.

Spark plugs look wet after several cranks but no starts. Timing light is not firing when cranking the engine over.  Fuel pressure at rail reads fine

I think I am getting fuel but no spark.  I suspect something with the triggers.

Is the crank trigger dead?  Is it a software programming issue?  Help!

Attached the scope picture and pcl file.  Thank you!

 

 

2016-06-21-S14-Fuse105-RCTS-CLL-MM.pclr

[Adamw]

Something is wrong with the trigger for the voltage to be so low. Most of your Trig 1 amplitude is only about 100mV p2p which is not enough.  Generally you would want a bare minimum of about 0.4V at cranking speeds.  Trigger 2 is not great but might still be usable.

The first thing I would look at is sensor air gap, has something moved? close it up a bit if you can. Check things like end float etc.  If that looks ok the next thing I would do is disconnect the sensor from wiring and connect your standalone scope direct to the sensor and try again.  That will eliminate a short or something in the wiring that could be "pulling it down". 

[jycheung]

Thanks Adam.  The air gap is 0.010'' measured by feeler gauge.  I'll check the standalone scope direct to the sensor and see but I checked my wiring with continuity and it all looks good   With crank mag sensor is it common to see readings at lower voltages with a failure and not complete loss of signal?

I think the sensor is a electromotive one

http://www.racetep.com/manufacturer/electromotive/complete-kits/tec-s/1-2-in-mag-sensor-round-point-w-connector.html

But it was sold by VAC motorsports which I have had poor experiences with.

Joseph

[Adamw]

With crank mag sensor is it common to see readings at lower voltages with a failure and not complete loss of signal?

I don't think it would be a common failure mode but I still wouldn't rule it out yet either.  VR sensors are pretty simple devices, basically just a coil of wire wrapped around a pole so not much to go wrong.  Do the isolated scope test I suggested and also check things that could effect sensor gap like crank end float etc first.  Maybe try another sensor if you find no problems with these.     

[Scott]

I think Adam is correct. The minimum value you can set the reluctor threshold table value to is 200mV, so any signal amplitude below this is going to be regarded as electrical noise.

Scott.

[jycheung]

Hi Scott and Adam,

Checked with external oscilloscope at the mag crank sensor and still get a similar tracing (<200mV amplitude <400mV P2P).  The sensor did not come with a data sheet however I think it is an electromotive crank sensor.  The sensor resistance between signal and ground wire is not within spec of the presumed sensor type.  So I'm going to order a new sensor and see if it fixes the problem.  Will keep the forum posted.

Joseph