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newbie helb with back fires in intake while cranking

Posted: Thu May 28, 2009 2:59 pm
by cricha5
Well, it runs. It runs pretty decent after it is started. Running MS2 3.0 with ms2extra code, wasted spark, 2006 ford duratec I4 engine.

Problem is with starting. First of all, I believe I have the tach signal wires reversed, since I can only get it to start by selecting falling edge rather than rising edge. I searched and have been unable to find if this really makes any difference to anything. Anybody know? I had to lean out the priming pulse and cranking percentage quite a bit, more than I think would be normal, to get it to start. Which I think is strange since I had to richen the ve table quite a bit. When I am cranking, sometimes (usually the first couple cranks), the starter will try and then just stop. Kind of like the timing would be way of and the engine is firing against the starter. Sometimes while cranking I'll get a little back fire into the intake and one of the little vacuum plugs will blow off. Sometimes it starts right up.

From what I can gather, and I'm not positive, the missing tooth is at TDC and the sensor is about 100 degrees BTDC, which is why I have the angle of tooth 1 set at 90 degrees in megatune. I tried changing this to 80 and 100 and could not get it started. I used a timing light for a moment and it seems like this is in the ball park at least.

Another thread said to change the Cranking Trigger from calculated to the other setting.

I will be that out and try swapping the tach wires, but I'm afraid of damaging the starter and the motor, so if anyone has any insight that would get me there quicker than my fumblings, I would greatly appreciate it. Thank you.

Re: newbie helb with back fires in intake while cranking

Posted: Thu May 28, 2009 4:11 pm
by Mad Medicine
From what i learned in school, backfires in the intake usually means you're running lean, or your timming is incorrect. when i started my car for the first time with the edis ignition, i placed the crank sensor at the wrong position (6 teeth after the mark, instead of 6 teeh before the mark)

But that was in my case (timining was very wrong and couldn't get it to start at all) you it appears to be running. You said in your post you leaned out your cranking pulse, i guess that's might be why. maybe somebody else can step in and give you help on this.

backfires in intake (lean)
backfires in exhaust (rich)