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Trigger errors and misfire


MartinS

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Hi Adam, just got back to work on things today, I've now stepwise plugged in a few more things into plug A. Attached is a scope with all of plug B,  plug A +12, both ECU gnds, both triggers, both signal grounds, and +5V.  As well, everything with +12V power powered up.

https://drive.google.com/file/d/1qytcVx6x3zuoeuWj_-jLldEtc9mZ_A4c/view?usp=sharing 

Still looks ok.  So is something leaking voltage into one of the inputs or outputs?  Is either more likely?  Given your knowledge of the architecture and these problems, are any candidates more likely to be a problem (ie ignition outputs likely, injection unlikely)?  Or are any of the remaining leads equally likely.  Just trying to get a systematic approach to  next steps and do a little less cranking....  

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I think I've exhausted all my hunches already with this one.  When you connected the 5V & siugnal ground wires, where the sensors at the other end of the loom still plugged in - TPS & MAP etc?  If not that is probably the next test I would try.  After that Im a bit lost so I would probably just try for example plug in all analog inputs, then all aux outputs etc.  

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Hi Adam, got down to looking for fault today.  What I had done is remove the 2 ground, 2 sensor ground, 2 triggers, +12V and +5V sockets from plug A and put them directly on their pins.  I also plugged B back in and with this, the crank trigger tracing was normal.

Today, I put all the above sockets back into plug A, plugged A into ECU, normal tracing.  Then removed A, plugged B into ECU, normal tracing.  Next plugged both A and B back into the ECU.  So everything plugged in.  Cranked, engine ran, abnormal tracing.

https://drive.google.com/file/d/1GUZi4WEoJzeOEZMGQNnWDoTOn2knTpj3/view?usp=sharing

Began removing sockets.  First, Inj 1-4 from plug A.  Abnormal tracing.

https://drive.google.com/file/d/1B1lLNabDivWjAYWgoe8KxIwjmU-U518L/view?usp=sharing

Next, Inj 5-8 from pin (Inj 1-8 now removed, everything else connected) NORMAL TRACING!  Pretty sure anyway:

https://drive.google.com/file/d/1KVDCj2OB8RNZN4Z-r7XnIrKW0_YIlB_9/view?usp=sharing

So, I stepwise replaced 8, 7, 6, then 5.  So back to same setup as only Inj 1-4 removed from A as above.  Now the tracing looks normal to me (engine starts half way through screen):

https://drive.google.com/file/d/1CQef2K9CvIt73uVD6jPah3eL9Ir4EUrB/view?usp=sharing 

Am I misinterpreting this?  I hope so because I don't see how it's possible: remove 1-4 and the tracing's abnormal, removing 5-8, normal, then replacing them and the tracing's normal in the same config it was just abnormal in?  I'm lost...

 

Ok, now I look at it more closely, with Inj 1-8, while the toothless trace is now symmetrical, the overall tracing appears to be shifted to +ve voltage. If so, the morphology has normalized but the voltage has shifted.  I can't interpret that.  

Sorry, with Inj 1-8 removed

 

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Been looking closely, the tracing seems to be symmetrical at the toothless zones even though it wasn't with the previous tracing with thee same pins connected/disconnected but it's definitely shifted significantly positive.  I interpret that to mean I need to keep looking...

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It looks to me like possibly injector 5-8 is the problem.  

The last picture were you have repined inj 5-8, the waveform is not bad in the cranking area, but when it starts it has gone all distorted.  I see you have E-throttle relay on inj7 and tacho on inj 8 so try leaving those out.  

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Remove 7 and 8; no change.

Have started to progressively remove 'blocks' of leads (mostly from plug A so far).  Here is a pic with a list of what's removed.  The engine runs surprisingly well on 2 cylinders(!) and I did all this running on cyl 5 and 6.  I then removed 5 and 6 and ran on 3 and 4 just to make sure nothing changed.  So far a pattern has emerged which is shown in the linked pic where the engine starts about 1/3 way through the screen. 

https://drive.google.com/file/d/1KNn0ucexch4_2S_TdGphNE3hhs3E6NwG/view?usp=sharing

With cranking, I have a pretty good tracing.  As soon as it starts, it looks like above pretty consistently.  I have pics at pretty much every step listed on the paper in the photo.  I'm going to go through in more detail but I didn't really notice any changes when doing it.  

Does normal tracing when cranking now and abnormal when running help in any way?  I can't think of the implications....

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These 2 tracings demonstrate what I mean about cranking vs running.  In these, the first pic shows the engine cranking.  Ign and Inj 1-4 are unplugged.  Inj 7 and 8 are unplugged as you suggested, Ign and Inj 5 and 6 are plugged in still.  

First pic shows the cranking and I got excited as I think it looks really good.  Then the engine fired and ran (on cylinders 5 and 6 only...and really ran surprisingly smoothly!) and the tracing in pic 2 shows the trigger tracing running and it's back to looking bad.   

https://drive.google.com/file/d/1RdpsYcZeByufbi4t9bUkrCrPrRP0yD0u/view?usp=sharing

https://drive.google.com/file/d/175_GAYqRoAU2sck4iaLQuuybp8eW2bHf/view?usp=sharing

Anything that can be inferred from this?

 

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The car will run on only 2 cylinders.  Can you tell me the absolute bare minimum I need plugged into the ECU to have it run?  

If it still has an abnormal tracing while running...I don't know.  But if it's then normal, I think it would be better for me to do what you originally suggested and start plugging things back in.  I'm getting to the point where I'm thinking unplugging more things will prevent it running and I can't tell if the tracing is good or bad because it'll be good cranking only.

 

For example, when I disconnected the MAP pin, it would fire but not sustain run.  Enough to see tracing was abnormal though.

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Will a new ECU fix this or is a Link ECU not able to run this setup?  Seems like it should be able to but...I've spent so much time on this one problem and have a significant financial investment in the vehicle.  I really just want to get the engine running and be able to use the vehicle which I thought was going to happen weeks/months ago.  I feel like I need to cut my losses.  With no solution in sight, what's my next best move?

I've spent in the neighbourhood of 20-30 hours on this problem in the last month.  

Should I replace all my ignition modules?  All my injectors?  Have another (3rd) new $180 crank trigger.  New cam position sensor(s)?  Not much else to replace as it's still not a good tracing with nothing else plugged in.  Can't test it at 2000 RPM to see if it still misfires and dies at 2500 RPM because all the e-throttle is disconnected.  I can get another engine for much less than replacing all the electrical items on the engine.  Is that the solution?  

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You can send the ecu in for a test if you like but my intuition is still not feeling much doubt about the ECU yet.  I agree ts definitely an odd one.  You have an acceptable looking waveform when cranking, but not when running.  From an ecu perspective I cant really think of much that changes electronically that could create the distortion only when the engine is running and not when cranking.  The ecu doesnt really do anything different between running and cranking - it is just pulsing injectors and ignition at the same crank angle every cycle.  

How about trying with the alternator belt off in case that is the culprit?

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Since cam position sensors are 12V and grounded to the sensor ground, I wondered if, like some other 12V supplied sensors, this was incorrect and they should be chassis grounded.  Although signal leads disconnected, signal grounds to ECU and 12V power to sensors still connected.  Disconnected the three currently unused sensors and grounded LH intake cam sensor to chassis.  Setup as above, alternator not in circuit.  No change in tracing.

Tested revs by manually opening throttle, hits 'rev limiter' effect around  1500-2000 rpm, much misfiring.  

I'm actually pretty depressed about this Adam.  The finish line, which I thought was in sight in May-June (admittedly delayed by harness and transmission issues as well...those have been solved for some time now), seems to get further away the harder I try to solve this.  Maybe I'm missing something but is there any chance this is going to work out?  

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House batteries have a shunt and are chassis grounded with solar and DC-DC charger.  Batteries in and out of circuit, no change tracing.  All tracings have been with house batteries off.  Have not tried disconnecting DC-DC charger but is connected directly from batteries to +ve post battery, seems unlikely to be an issue.  

Small 600W inverter has been off entire time. Only commonality is same attachment point for ground as strap from transmission.  110V mains only supply socket in living area, used for battery charger for engine battery.  Plugged in or not makes no difference.  

Power supplies for the engine through a series of 5 relays controlled by ignition switch, each one separately: ignition, ecu, fuel pump, e-throttle, and voltage feedback to alternator.  Can't remember which one also has Wideband controller.  Not a complex supply, can take pic of circuit diagram if helpful.  

Starter has a lockout relay which is controlled by a security device.  Circuit only connected to starter solenoid.  

No other circuits associated with engine/ecu.

Bought and installed new socket to plug into crank trigger.  Wired direct from crank trigger to Link wiring loom with new shielded cabe.  Should I run this from trigger sensor directly to the ECU bypassing the Link loom?  

On 11/7/2021 at 2:53 AM, Adamw said:

You have an acceptable looking waveform when cranking, but not when running

Looking more closely at the tracings, whether cranking or running, the voltage is shifted from the zero point to the +ve side by a factor of 1.5 (always 1.5 times more positive than negative).

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2 hours ago, MartinS said:

Bought and installed new socket to plug into crank trigger.  Wired direct from crank trigger to Link wiring loom with new shielded cabe.  Should I run this from trigger sensor directly to the ECU bypassing the Link loom?  

That would be a worth while test too.

I've just bounced some ideas off Simon our head Tech and we both think it is now worth getting this ecu back for a test.  If you email [email protected] with the subject "G4 Xtreme for trigger circuit inspection" and just give them a link to this post so they have some info on the troubleshooting that has been done so far.  They will send you a service form to fill out and instructions on where to ship it.  

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Hi Adam,

Well, it's been mid Nov since I was able to do anything with this.  In that time, the ECU has been shipped to Detroit and tested by your tech team and found to be functioning without fault as you thought.

I have spent a bit of time researching possible solutions and changed my engine and all engine/ECU ancillary equipment to a star grounding system with all grounding through one point on the engine block and back to the battery via welding cable.  

Re-installed ECU today and tested: no change in engine behaviour.  Misfire and trigger error counts starting at around 3000RPM.

Not sure what next.  I did have the engine wiring loom off the engine when I was prepping the engine for install at which time I cleaned and inspected the loom, replaced some plugs, and tidied up with loom tape for re-install.  Do I need to go through it again?

The only sensors I either haven't replaced or run without are the LH intake cam position sensor and the MAP sensors. Should I get a new cam sensor?  New MAP sensor?  

Is there a next step I am not seeing?

Cheers,

Martin 

 

 

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Spent weekend removing engine harness, removing all coverings, cleaning and inspecting all individual wires, and re-covering/insulating. Found a couple of very small nicks in wires and repaired, didn't appear significant though.  

Will re-install and test but strikes me unlikely to have helped.

 

https://drive.google.com/file/d/1UksUG7AmuBffU3bGLmgIVhApd24oDBNo/view?usp=sharing

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