Ignition timing

You cannot adjust the ignition timing. Most current model vehicles do not allow any such adjustment as it is up to the engine ECU to manage that, based upon vehicle speed, engine temperature, accelerator pedal position, knock sensor readings, etc.

 

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Hi Patrick,

Do you know the spec for correct timing for cylinder #1 fuel injector and spark? The picture below is of cylinder#1 fuel injector and spark. Notice the fuel injector gets turned on two cylinder strokes prior to the cylinder #1 spark.




Here's an example of an engine that is failing to start the engine. Notice the fuel injector gets turned on at a different time. Any help is appreciated.

 

Timing for the fuel injector pulse is mostly irrelevant- the only thing that matters is that the fuel gets into the cylinder. You have three copies of the same scope capture (why?). All show the injector pulse happening around the beginning of the intake stroke.

Ignition timing is more critical, but without a TDC reference, your scope captures don't tell you much. Really, scantool data would be more useful for that.

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Is there a signal that I can capture with a scope that will show TDC reference?

 

I've attached the autel data for reference.

 

On page 4 of this article you can see some examples of ignion traces combined with a crank position sensor trace.

 

1/31 diagnosis:
Additional diagnosis performed:
- checked fuel pressure again - 50 psi
- checked air suction at throttle body - good hand suction at throttle body when putting palm over throttle body opening
- removed injector connectors from all 4 injectors and added starter fluid through throttle body - car did not stay on. I've been told this would keep the car running as long as I keep injecting starter fluid in the throttle body.
- removed coils and put a screwdriver in it then held screwdriver body about 1/2" away from engine cover to check for strong spark. Strong spark witnessed.


I will generate the same graphs in addition to the camshaft sensor tomorrow (2/3).

 

2/3/22 diagnosis

- I did perform the fuel pressure test during startup. Fuel pressure stays at 50psi.

- Here are the captures I took today from the bad vehicle. I'll have to capture the good one tomorrow.


I offset all data from 0, except spark #1, so you can see everything in one chart more clearly. Per spec, camshaft has three cycles per two crank engine revolution cycles. I'm too zoomed out since the crankshaft should look more sinusoidal.

 

Get a functioning techstream. Then you can post useful data.

 

This is neat, but doesn't provide much info concerning your problem. Yes, cam and crank sync are close - but wouldn't run at all if it was way out and I would expect codes if it was off enough to affect running significantly. I would need to see a known good to know if ignition timing is close or injector on time is normal.

Or you could record and post some scan data. Might be faster that way. Then you can get a direction to investigate which might need your scope.

PS, prius makes lots of EMF noise, you can get a cleaner waveform sometimes by (briefly) shifting the car into neutral- that "turn s off" the inverter.

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what data would you like to see beside the computer data i've already shared above.

 

You have resurrected a 10 year old post and posted alot of meaningless screen grabs. Waste of time.

You do not have any codes the car has thrown. It has thrown many. Techstream or Dr Prius for harvest of OBD codes.

 

Ok as promised here's the data I took

Here's the bad engine - the one that doesn't start.



here's a capture of the known good engine

You're not being productive. Specially when you're asking for codes that I have already posted in full detail in pdf files above. The computer codes or details are no help. I'm down to posting engine timing because I've exhausted all other options.

 

Well, I'm not seeing much difference at all in the ignition timing between bad and good.

I don't have a ready explanation for the difference in injection timing, but as mr_guy_mann suggested in #5, I'm not sure how critical the injection timing is. (Meaning exactly where in the cycle it injects; the duration is critical of course.)

I'm getting around 1260 RPM for the good engine and 960 for the bad one just being cranked; I wonder if the injector timing gets adjusted for that.

 

TDC, I am guessing, would be right at the left edge of cylinder #1 spark (green trace).

I certainly ran out of options at this point of what to look for. The only thing I haven't checked in this new engine is checking engine compression for all cylinders. Any other ideas would be appreciated.

 

Spark is probably several degrees BTDC. If you were really looking to pin down TDC, I think that would take working from the crank sensor.

If there hasn't been a compression or leakdown test, that gap might be worth filling in.

There was another thread just recently where somebody acquired an engine that wouldn't start because it had been apart and reassembled with the valve timing wrong, discovered late in the game because nobody had mentioned it ever being apart.

 

I know engine well. I owned the car the engine came from. No issues with the engine prior to me putting it in this new vehicle. I performed compression testing on this engine as promised. It’s sitting at 53psi. No issues there.


I looked at the spark plugs again and they look dry. I opened the fuel line, during startup, to empty out fuel to a bucket and the flow was not as expected. The purpose of the test was to witness fuel flow. I’m going to setup an external rig to pump in a steady 50 psi of fuel to the engine.

another observation, when the car went to ready I Noticed fuel pressure stayed at 0psi on the fuel gauge. The fuel pressure went to 50 psi only when the car started to crank the engine. I expected the fuel pressure to go to 50 psi when the car went to ready. I also expected the engine to start when I pumped in starter fluid in the throttle body, so what do I know…

 

53 psi compression? Is your gauge accurate? That's way too low. Spec is 128 standard, 99psi minimum. That's at sea level barometric pressure. Higher altitudes will reduce the compression gauge readings proportionally to the drop in baro.

The "compression test" function on a scantool is weird. The ecu spins the engine for 5-6 compression strokes @ 950 RPM (I get 135-140psi at 700ft elevation on my 2006) then does another 5 compression strokes at 200 RPM. Don't know why they did it that way. It's tricky but possible to vent the gauge at the right time and capture the lower speed pulses if you want- I got 90-95 psi for reference.

Also, when I say I would like to see scantool data, I am specifically talking about saving a screenshot or whatever of live data when the engine is running. One capture at about 1000 rpm in park, then another with throttle fully depressed- should go to about 2500. I am not sure how the autel goes about saving live data. There is a "record movie" function, but again I'm not sure how (or if you can) save it and view later.


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