coolant temp and/also load. These 2 tables I am looking at in TC $6E and $32B cals. But what conditions do these tables actually get used? IE do they get used during engine crank? Or maybe just after it is started, before it gets warmed up enough for closed loop.

What about PE conditions? There are other tables for PE mode, but I read that these tables are also used.

 

they are used all the time. engines need to run richer cold. yes they affect pe but only when they are used to correct a/f ratio for variying engine temps.

 

Ok got to consider these tables as well for engine crank. I checked my stock '88 bin, and compared the table values to the ARAP in F/A ratio % vs coolant table. My stock bin actually had higher %change numbers overall, and that is with a cold-start injector.

Does anyone think that lowering these % at warm coolant temps would really affect long engine crank times? Of course I have been playing with all the crank fuel tables, even recently changed the bat to help her spin over faster when warm. Still no luck. I got to get some more scan tool data.

Maybe that WB will have to go in sooner than this winter!!

 

The Open Loop Fuel/Air %change vs... tables are only used during open loop engine running. Once in closed loop the commanded AFR is 14.7.

During crank the ECM uses a derived PW based on a couple of tables. The MAF isn't even used during crank, therefore neither are any of the tables associated with it.

If your problem is long crank times with ARAP do a search on 'ARAP' and 'crank'. Should find a post that describes which table to change. It is a table that is crank PW vs DRP pulses or such. ARAP doesn't start to inject crank fuel until a certain numebr of DRPs are counted.

RBob.

 

The Open Loop Fuel/Air %change vs... tables are only used during open loop engine running. Once in closed loop the commanded AFR is 14.7.

This is what I wanted to hear, Rbob. 2 less tables to worry about.

If your problem is long crank times with ARAP do a search on 'ARAP' and 'crank'. Should find a post that describes which table to change. It is a table that is crank PW vs DRP pulses or such. ARAP doesn't start to inject crank fuel until a certain numebr of DRPs are counted.

I have allready been there done that. My problem is long cranks when engine is WARM. When it is cold, or at ambient temp, she fires up in less than a second. After it is warmed up normal, and I go park for an hour, it will crank 3-4sec before firing.

Tonight I lowered the %change to F/A at startup table values at 44C thru 116C to 3.1%. I have been playing with all the crank fuel tables. I have the IAC startup park postion set to 160. I think I need more air and/or less fuel.

I could post all my tables if it helps you.

Need some ideas.

 

Might wanna verify that the fuel press isn't dropping quickly after shut-down. A leaky inj will flood eng and cause a long crank time.
If eng sits long enough, the fuel will evaporate and eng will start normally again.

 

I have a FP gage mounted on fuel rail permanent. It takes about an hour for pressure to fall to 0. My injectors were sent out for cleaning and flowtesting a cupala years ago, so they should be in good shape. I recently replaced the battery and fuel pump relay.

In theroy when you shut off engine, the injectors are shut off immediately. (no pulse width) so there should be no extra fuel in chambers like a carb would have.

If i restart the car after a minute or so while it is warm, it will fire right up.

Also I am getting into the habit of turning key to run for a partial second, then going to start. This gets the fuel pump primed up nicely.

Keep the ideas coming.

 

I'm not aware of an official spec for "fuel press bleed-down rate", but that seems excessive to me, especially if all the fuel is bleeding past the injs (as opposed to leaking past the regulator or back thru the fuel pump).

As a test, you could warm-up eng, shut it off and let stand for 30-60 mins. Remove the fuel inj fuses and try to re-start eng.
If the eng fires a couple of times, the inj/s are leaking into the intake port.

Another test, that might tell you something, would be to warm up eng and kill it by unplugging the fuel pump. That would remove all the fuel press from the system. Let eng sit for 30-60 mins. Reconnect fuel pump (with ign switch off), and try the warm start-up again. A leaky inj can't flood an eng if there's no fuel press.

Are you running a cold start inj? If so, try unplugging it for a warm start.

 

When you mean "excessive", what exactly do you mean? Too long of a time to bleed the pressure down? Or should it be hours to bleed down? I would think that a really bad leaking injector would take only 5-10 minutes to bleed the pressure off.

When I had them cleaned and flowtested in March of 2000, 1 injector was found to be a "dripper" before cleaning. But that was supposedly fixed during cleaning. So maybe that one injector is going bad again.

Now for the tests you mentioned. For the first test, the pressure was about 12psi after 60 min cooldown, coolant about 150. I pulled the 2 injector fuses and cranked it up. It DID fire for about 1sec, then just cranked. So maybe a small leak.

For the 2nd test, I did disable the fuel pump and let the engine die. After about 55min, the coolant was at 155, then I tried cranking again.(with FP connected). It fired up nicely, like it does when it is stone cold!!!

So maybe we are on to something.

I havent run the cold-start injector since 2 years ago.

Lets continue this topic offline, ZZ28, since it is getting off the original topic.

Email me or send me a PM.

Thanks much!

 

I agree. You've got PM!