How'd it go Mr. Fred?

 

I think I've got a pretty good case for the culprit being leaky injectors in combination with high post shutdown fuel rail pressure. I first monitored fuel rail pressure for 1.5 hrs after shutdown and then started the car. Crappy start as usual... took over 2 seconds for the motor to light up. After that, I drove the car around for about 15 minutes to get it completely back up to temperature, shutdown the car, pulled the FPR from the rail to relieve the rail pressure, and then let the car sit for 1.5 hrs again. After reinstalling the FPR into the rail, I started the car. This time it fired up pretty well. It wasn't perfect, but it was worlds better than the previous attempt. Note that in both cases, the coolant temp was around 125 F just before I started the car.

I probably need to repeat the experiment in reverse order to really convince myself that I found the cause. Also would be good to have other people duplicate the experiment.

The first graph shows what happens to fuel rail pressure in my car after shutdown. Note that the car was shutdown for about 5 minutes before I remembered to start the log. The second graph is a follow-on to the first graph and shows crappy startup after sitting for about 1.5 hrs.

The third graph shows rail pressure and coolant temp in the instance where I pulled the FPR from the rail immediately after shutdown. The graph shows rail pressure and coolant temp 1.5 hrs after the car had been shutdown. The last plot shows the startup response after sitting for 1.5 hrs with the fuel rail vented. Note that the starting rail pressure is 0 psi. The car doesn't light off immediately, but it was pretty quick and always going in the right direction.


rail pressure and coolant temp monitored for 1.5 hrs after shutdown


startup response 1.5 hrs after shutdown



rail pressure and coolant temp just before startup after 1.5 hrs with rail vented


startup response 1.5 hrs after shutdown with vented rail during shutdown

 

Nice. Now we have focus point.

Combine leaking injectors with:
e85 vapors dont fire well?
e85 tight spark plug gaps dont help?
small battery reducing crank power?

everything I observed with my car suggests these injectors leak after shutdown.

 

Time to add my stew to the mix...

Installed the ID1000s.

I used the following scaling

Injector scaling 812
3.816
3.144
1.944
1.392
0.984
0.72
0.504

the above values were taken from Rawkus..

Now my car sustains fuel pressure .. approximately 25 psi after shutdown... it will dissipate after about an hour..

The car starts up everytime on the first click when it is cold..
If the car is warm..it struggles slightly , I would say 2 secs of cranking .

Let me know if I can be of any assistance in providing data to you guys.

 

After looking at MrFred's data I think this is a pressure issue. I remember travis saying that one time he relieved his fuel rail pressure and the car started fine. Also, for all I know my flowback check valve in my walbro is leaking and reducing fuel pressure upon shutdown, hence why my car starts fine.

It must be a combination of heat soak on the injector coils reducing the ability to crack open with the fuel pressure in the fuel rail.

 

Yes I did relieve the pressure in the car as well (2) nights ago and the car started much better.....not perfect but acceptable and I too want to do this a few more times to convince myself it worked. I also noticed the same trend as Mrfred about the FP rising after shutdown - doesn't seem to do it all the time but I have witnessed it myself on my FP gauge.

I have (2) ice packs I will be placing over the injectors when i get home from work for 30 min to see how much of a role just temps have in this as well.

Dan I may buy one of those pieces mrfred has for mounting the fuel pressure gauge and change my FP setup a little - if I get one maybe we can swap it in your car some weekend because your car is the one that is fine and to know what it does would be a HUGE help...

 

Did you adjust your ipw startup enrichment table (now called "first pulse") at all?

Also your FP situation seems normal - when I shut down im anywhere from 28-32 psi and in about 30ish min its to zero most times I believe (will confirm). My original FPR bled down much faster than the new one I installed when I originally thought it was the FPR causing issues.

 

No I did not adjust the IPW start up values..
The only things that I changed were the scalings and battery latencies...

I can get some more accurate FP information for you , as I have an electrical FP guage in the car.

p.s ROM ID is 94170015 and it is virgin... no tephra mods, or anything else.
Oh and I am on 92 octane as well.

 

Sounds good travis, but remember the car is going into winter storage soon.

I think the evo might heat soak the coils a lot more than any other application and that combined with high fuel pressure upon shut down (due to fuel expansion) might cause some issues when the injectors are trying to open.

 

Have you guys seen this quote from the service manual?
looks like the ecu intentionally raises fuel pressure via the solenoid on the FPR vacuum line during warm starts. I wonder what else it's doing when it does that?

 

Yes I've left my fuel pressure solenoid installed. I'm assuming that's the first thing anyone would try if they had warm starting problems, re-installing it if it had been removed.

 

yup tried it....was the second thing I tried, mine is installed still - I tried unplugging it and hooking the FPR direct to the IM but it made no difference.

 

Nice find. The increased fuel pressure can be seen in my startup logs.

 

Travman,
Did you see my post about cooling the fuel injectors? I did that already... it helped. Still not perfect. Check out the video compared to the day before's start

 

Yea i know - still like to experience things for myself. Also seems you did a bunch of other stuff as well at the same time. I am going to isolate the situation to temp only for my own peace of mind...