Hard start

[Abomb]

I have a v7 sti and picked my car up from the tuner today. It has a 20g with 850cc injectors and a 255 walbro. It’s not starting well, it’ll crank 5-8 seconds and not start. It’ll also occasionally backfire while cranking. I have -18 vac at idle so there isn’t a leak, is this a timing issue with the starting tune or am I looking at a different problem?

[Adamw]

Can you do a PC log of a startup and attach that and a copy of your tune here.

[Abomb]

Ok, I’ll have to sort out my home laptop for that. I’ll post it when I get home from work. 

[Abomb]

I’m at my tuner. It’s a trigger 2 issue. It’s not telling the engine when to fire correctly as when it won’t fire, there is no sync with trigger 2. 

[Abomb]

Also he’s  had to change it to optical Even though it’s a reluctor.

[Adamw]

Your ecu has a trigger scope, please use it.

[Abomb]

We’ve stopped for the night, I’ll pass on that info for Tuesday. 

[ripspeed]

It will not start if trigger 2 is set to Reluctor as it should be. It will only start if trigger 2 is set as Optical/hall. It is still very intermittent to start even then, but when it wont start it does not see a trigger 2, cycle key of & on a few times & it will then get a trigger 2/sync & it starts?

Pattern is good in trigger scope.

[Adamw]

Please give us a triggerscope.  If you need to change to hall to get it to run then it means the ECU is not happy with the pattern it is receiving when set to reluctor.  AVCS control will be very poor when set to hall.  It could be anything from arming threshold to cam timing to a wiring problem.  The triggerscope will help us determine which of these you need to look at.

[ripspeed]

Car is not here now. I tried to save the trigger patterns in the software but it hasn't saved.

Played with arming thresholds for trigger 2, anywhere from 0.5 up to 2v under crank, no change. It sees trigger 2 when logging it everytime in the logging when switched to reluctor, just wont go?

From memory under crank the peak was approx 1.5-1.8v for trigger 2. 

Change back to optical/hall & it goes, intermittently? Surely it should go at all with it set to Hall/Optical since it is in fact a reluctor sensor?

Car ran fine on stock ECU, no hard start, no miss-fires so I believe that you can rule out a cam timing issue.

When he drops it back on Tuesday I'll have to capture the trigger again. Do you just want a screen shot or is there another way to save it?

.

[Adamw]

No, click the save button, that will save it as a log file.

[Abomb]

Tomorrow before work I will log what you’re asking but it will be strictly to get ripspeed as much info as possible, I’m not willing to risk any of his work due to my ignorance when it comes to making changes or uploading amended files. 

[ripspeed]

Two trigger scope captures & one log attempting to start with it set as to reluctor.

B Knight Trigger 2.llgx B Knight Trigger 3.llgx Trigger as reluctor NO GO Log 2020-05-29 6;20;42 pm.llgx

[Adamw]

Ok the trigger scope looks quite alright.  There is a small 0.2V spike on the cam signal but it looks like arming threshold will take care of that.  

You are on very old firmware so I suspect you are just 360 deg out on your offset (firing on exhaust stroke).  By changing to hall it possibly mis-syncs sometimes and fires on the correct stroke.  This would explain why it doesnt start reliably - with it mis-syncing it will be something like a 50/50 chance of it firing on the correct stroke.

So either update to the latest firmware or add or subtract 360 from your trigger offset and check base timing again.

 

Edited May 29, 2020 by Adamw
spelling

[ripspeed]

Sweet, thank you I'll try that.