Corvair hard start

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Corvair hard start

Postby fatcorvairman » Sat Jan 13, 2018 2:35 pm

Hello all,
I am new to the forum but have searched and used the topics to help me with my MS3 3.57. I have a 1965 2.7L Corvair Corsa with sequential fuel injection, a chrysler IAC, an AEM O2 controller and an AEM EPM puck. I have been able to get the engine running but only after 10's of minutes of cranking and manipulating the throttle. I have made various changes to the IAC crank steps, the cranking pulse width setting , and the afterstart enrichment setting. All of this to no avail. Hot or cold it takes minutes of cranking to kind of start and then I have to manipulate the throttle to keep it running until it "catches". The fixed 10
degree timing lines up perfectly The idle tune works great and I have been driving around trying to autotune different parts of the map. I have not applied over 3psi of boost yet. Is there anyone out there who has worked through this problem on an air cooled engine?
Thanks
John
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CORSAinitial_2018-01-13_12.14.29.msq
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Re: Corvair hard start

Postby billr » Sat Jan 13, 2018 6:16 pm

Post an MSL of a couple of starts.
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Re: Corvair hard start

Postby fatcorvairman » Sun Jan 14, 2018 9:40 am

Here are two attempted starts cold. I lost the battery trying to get it started today or I would have included a hot start attempt.
Thanks
John
Attachments
2018-01-14_08.59.49.msl
(167.87 KiB) Downloaded 1 time
2018-01-14_09.00.49.msl
(104.27 KiB) Downloaded 3 times
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Re: Corvair hard start

Postby billr » Sun Jan 14, 2018 9:49 am

Are the plugs pretty wet with fuel after one of those long (10 sec) crankings?

The MAP is dropping low enough during cranking that I think the engine is starving for air. Either open the throttle stop or increase the cranking IAC steps.
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Re: Corvair hard start

Postby fatcorvairman » Sun Jan 14, 2018 10:00 am

Bill I didn't check them this morning but they have definitely been sooty in the past. I have changed the cranking IAC steps all over the scale and no setting works better than the others for cranking. Opening the throttle helps but it dies immediately afterward. If I pulse the throttle (sometimes) I can keep it running for a few seconds. Usually after 10's of minutes of this the cylinder heads heat up enough (170deg) and it starts.
John
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Re: Corvair hard start

Postby fatcorvairman » Sun Jan 14, 2018 10:20 am

Bill,
I am going to check my IAC setup again. If I remember correctly my A and B coils were wired opposite. I thought I could just set the IAC homing to 'closed' in order to fix this. Though the engine seems to run OK with this configuration, I wonder if it is affecting the cranking steps adjustment somehow.
John
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Re: Corvair hard start

Postby jsmcortina » Sun Jan 14, 2018 10:40 am

Use the idle valve test mode. Make sure that more steps (or duty) gives more RPM.

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Re: Corvair hard start

Postby billr » Sun Jan 14, 2018 5:02 pm

I see your stoich is 13; what fuel is that?

Lower the cranking threshold from the present 500 rpm to just a bit above actual cranking speed; like 250-300 rpm.

I would probably disable the IAC, disconnect the stepper and plug the inlet to it, until things are more stable.

If you disable fuel (kill 12V power to the injectors) and try a start with a quick blast of starting-fluid, does it quickly fire up and run briefly?
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Re: Corvair hard start

Postby fatcorvairman » Mon Jan 15, 2018 9:02 am

I used the IAC test mode with a spare throttle body to check my IAC setup (again). Though I have the idle control homing direction set to 'closed', the idle test mode homing opens the valve all the way. I'm confused. If I use the homing test shouldn't it follow how I set the idle control homing in the settings?
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Re: Corvair hard start

Postby fatcorvairman » Mon Jan 15, 2018 9:05 am

Bill,
I have adjusted stoich to 13 because this corvair is air cooled and runs much better in the 12.5 to 13 range. Thanks for the starter fluid test I will try that this morning
John
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Re: Corvair hard start

Postby billr » Mon Jan 15, 2018 9:59 am

Set the stoich for the correct value, and set the AFR using the AFR table.

Reverse the IAC by swapping the two wires on (only) one coil of the stepper.
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Re: Corvair hard start

Postby fatcorvairman » Mon Jan 15, 2018 10:07 am

Thanks Bill, doing that right now - also readjusting my cranking and warmup steps. IAC was all backward. I will also readjust stoic.
John
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Re: Corvair hard start

Postby fatcorvairman » Mon Jan 15, 2018 10:39 am

IAC is normal (all closed at 0 steps all open at 205 steps), stoic is back to 14.7, new msq and msl's
John
Attachments
CORSAinitial_2018-01-15_10.36.44.msq
(275.41 KiB) Downloaded 3 times
2018-01-15_10.36.01.msl
(120.61 KiB) Downloaded 2 times
2018-01-15_10.36.24.msl
(96.33 KiB) Downloaded 1 time
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Re: Corvair hard start

Postby billr » Mon Jan 15, 2018 11:17 am

You need to recalculate the "req_fuel" now that the stoich is correct. The req_fuel is 19 with the stoich at 14.7, but do you actually have gasoline, or is it the common E10? E10 has a stoich closer to 14.2

Your cranking pulse is now pretty low. It is about 1/3 of what it was before, that is a pretty drastic drop.

Use more homing steps, even double what you think it may need. You want to deliberately stall the IAC motor against the seat when homing, and stalling won't hurt anything.

I suggest using "always on" or "holding" for the IAC current control. It often gives more reliable operation of a stepper.
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Re: Corvair hard start

Postby fatcorvairman » Mon Jan 15, 2018 12:48 pm

Bill,
I am running mostly 10% ethanol. I will re-calc using 14.2
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