Very difficult Starting

[Isofouet]

Hi,

I have a starting issue with my S15.
It's very hard to start, cold or warm. I have to crank durng a long time, and open the throttle a little bit during the cranking to make it start.

My mods are :
- Z32 AFM
- Nismo 740 cc
- Tomei M7960 turbo
- Tomei 260 cams
- Nistune remap

When the car is started, it runs quite good. The AFR are ok (I have a wideband), throttle response is good, closed loop is working.
When driving, I just have a problem with the idle on deceleration : I stall when I release the throttle. But, if I manage to keep the engine alive, it idles right.

I tried basically to put a base map, change the injectors and AFM, and of course tick the boxes "adjust cranking tables"
When it has started, I set the K constant, this is OK... but I still have difficulties to start. Here is a video :

https://drive.google.com/file/d/0B_F4FH ... sp=sharing

I assumed there were to much fuel, as I have to throttle and as I find fuel on the plugs after a failed attempt.
I tried to remove fuel from the crank enrich table, but it was worse.
I tried to change the engine cranking pulse offset. It was a bit better by adding fuel, that's weird...

Here is my test map :
https://drive.google.com/file/d/0B_F4FH ... sp=sharing
The fuel map is not the good one, it was a specific map for cranking tests

I looked at the injectors. They don't leak. The spray seems to be quite important, but I don't really know if it's normal or not.

The spark plugs are not very nice, but not completly dark. The sparks occurs, I checked the 4 of them :
https://drive.google.com/file/d/0B_F4FH ... sp=sharing
The starting was a bit better when I cleaned the tips of the plugs with fine sand paper.
I will change them anyway.

Right now, I'm out of ideas... I'll try to put back the oem injectors and AFM... we'll see...

Thank you

 

[spoonman]

you mentioned it was a bit better when you added fuel after altering the pulse, and your plugs are not a burnt mild brown more towards black as in your mixture is rich??..... basic question, since you are using the afm have you checked the recirc line and BOV, for air exiting and not making it back to the pre turbo intake and in turn causing your mixture to run rich when you lift your foot off.

 

[Isofouet]

The plugs are a bit dark, but not covered by black burnt fuel... But, maybe they aren't in a good shape...
The AFR are ok when the engine is running, the problem is only during the cranking...
I have an HKS dump valve, so no recirculation

 

[tooley]

You really need to get it compression tested! what you have described sounds compression related.

 

[Auss15]

Has the Nistune been tuned for non recirculation of blow off valve (dump valve) air ?

 

[Isofouet]

What parameters do you change for a BOV ?
Anyway, it should have minor effect on cranking...

I have to test the compressions... The engine has a brand new rebuild 400km ago... but who knows what could have happened during the running in.
Especially, I had a major oil leak on the road, and lost about 2L of oil (luckily, I have a bigger oilpan)... I hope it hasn't burned my rings... because I could start easier before...

 

[Auss15]

If you are venting the BOV to the atmosphere you have to change the AFR's on closed throttle as that air is measured as returned if you are recirculating, it's over fueling to compensate for the lost air...