Hard Starting and Flooding

[dhegge]

Hello I have a speedpro bank2bank/w wb02 on a 93 LT1 Supercharged Vette running a moderate 5PSI of Boost. I am having a problem with getting the car to start reliably.

When starting cold you have to crank the starter for a good 10 seconds before it starts. I was told that I should add some fuel in the cranking table which I did. It did not seem to make much difference so I added some more... than obviously I had to much because after the car started it was definitely flooded tons of black smoke etc.

Are there other parameters and/or tables that I should be manipulating in addition to the Cranking fuel enrichment table. Also my IAC is still set extremely high around 200 in order to allow the car to Idle properly.

Other than that driveability is good... and WOT is excellent!

BTW, after the car gets warmed up it starts as expected. What am I missing?

Doug

 

[bobc455]

It took me a while to get starting parameters sorted out.

There are two important settings: IAC position during starting (i.e. the amount of air) and injector PW (amount of fuel).

I used the following (rough) procedure:

1) Try to get the ratio right between amount of air and amount of fuel. This is basically trial and error. Pick an IAC setting that seems reasonable (maybe a little more than what you're running at idle?) and set it there- then fiddle with the injector PW until the engine starts easily. I had to go through this once for cold starts, then once for hot starts, then just kinda made a logical curve between the two points. Since your hot-starts seem to be okay, it's probably just the cold settings that you have to futz with. I would start by concentrating on the injector PW rather than the IAC setting- for now just get it to start, then play with IAC later (see step #2).

(A long time ago, someone told me that you need an A:F ratio of about 5:1 for starting cold, and more like 10:1 when hot. But those numbers are kinda irrelevant for doing this, just try to find where the engine likes to start).

2) Once the engine starts consistently, see if the engine surges after starting. For example, if the engine revs up to 2000 RPM just after starting and then settles down to the regular idle RPM, then you have too much air *and* too much fuel- back them down together (proportionally). so that the engine shoots to just 100-200 RPM higher than idle speed.

3) If the engine takes too long to settle down to regular idle speed, there is a setting somewhere for that too (I think it's called after-start decay), but it probably won't be an issue.

Because you have your IAC at 200 just to idle, I wonder if you need a bit more opening of your throttle plate(s), there may be some sort of mechanical adjustment screw for minimum throttle opening? (Kinda like setting the idle speed on a carb, there is a setscrew that limits how far the throttle plates will close). I have my IAC around 30 for idleing (when warmed up), and this is adjusted with the throttle stop.

-Bob Cunningham
bobc@gnttype.org

 

[Craig Smith]

Sounds to me like you definitely need more throttle blade. If your IAC is open that far just to get it to idle, the throttle blade must be all the way closed. It will always be very hard to start that way. I bet if you crack the throttle a little bit it fires right up.

I would recommend that you open the throttle blade until the IAC target position is at about 20 or 30, in park, fully warm.

Craig