Megasquirt Support Forum (MSEXTRA)

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

Post an MSL of a couple of starts.

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

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.

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

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

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

James

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?

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?

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

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.

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

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

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.

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

Still can't make this thing start no matter what I do. I put larger injectors in recently. still no luck. Rapidly burning up my starter and battery. When i adjust cranking pulse width up to 500% the plugs don't even get wet. Its the same old thing- if I feather the throttle and crank for 10's of minutes (between battery charges) eventually it catches and runs (when the head temperatures reach close to 200 degrees (air cooled)). Any suggestions?

Forgive me if I am asking questions already covered:

Has compression been checked when cold?

Do you have spark at all plugs when cold?

Has spark timing been checked (again, when cold)?

Since the plugs seem dry, how about fuel pressure, has that been checked? Has injector pulsing been checked with a meter or noid light? Even better, pull an injector and make sure it is spraying during one of those not-fire episodes.

Have you tried getting it to fire using starting-fluid?

Have you set the idle stop up well-open so there it will idle quite fast, ensuring plenty of air while it is cranking?

Getting an engine to run sweetly throughout it's operating range can be a real challenge; but getting it to fire... not so much. There has to be something very basic that is wrong here.

PS: I don't think it being air-cooled is relevant to getting it to fire cold.

Thanks Bill,
Timing was 30 deg atdc! Still investigating but adjusting the distributor makes it kick over immediately. I successfully set the distributor once before something definitely changed. Thanks for asking me to check that again!
John

Bill,
Thanks for the list of stuff. You most certainly were right... It was something basic. I am perplexed however, as to how the timing changed so radically since I set it up in December. Is it possible for the timing to somehow slip in the MS3?
John

Has the dizzy ever been removed? There is always the possibility of getting it back in a tooth or two off (teeth on the drive gear from the cam). People often chase that by "twisting the dizzy" until the rotor points at the proper cylinder tower in the cap, but that doesn't fix the now-wrong relationship of CMP pulse to crank position. Same thing even if you have a missing-tooth "crank wheel" in the dizzy; you have to get the dizzy back in as intended, or revise the "tooth #1 angle".