Rebuilt CA18DET Problem Starting When Hot (Only sometimes)

[tatsurou]

So I have my Ca18 fully forged and it runs well. Barely broken in, done only 30miles with it. It starts fine when cold, when you shut it down and turn back on it starts normally. However, sometimes, it will not start once it warmed up, it just barks and proceeds to crank like there is no spark at all for ages (spark present) and smells of fuel. Then after 20 minutes of cooling down it will start hesitant, but when cold it will start like nothing ever happened. It happens sometimes as other times it works just fine. I replaced Coolant temp sensor, idle seems adjusted, compression ok, headgasket new, head is rebuilt. Hot Air Solenoid is disconnected at the moment, no Carbon Vapour Tank. New spark plugs. No power mods, so far rebuilt T25 - so pretty much stock powers until it breaks in. Things I haven't checked yet - CAS? Ignition Box? Coils? What else to look for?

[pointz]

Sounds as though its flooding, was the cylinder head reconditioned st the same time?

[tatsurou]

Yeah it was. Tested, skimmed, new valve seals, valves seated etc. I also replaced the second coolant sensor - the two pin one. 5 times it started no problem, although when it starts the rpms drop to like 400 for 10 seconds then they go back up to normal. What I noticed is that when it doesnt start it barks off for 1 second then that rpm drop makes it die. Then you can just keep cranking forever. I'll try swapping a FPR and see if that makes any difference. Also forgot to mention - I got Walbro 255 and stock FPR

[green_rs13]

next time it does not want to start whip the spark plugs out and see if they are soaked in fuel.

[tatsurou]

next time it does not want to start whip the spark plugs out and see if they are soaked in fuel.

Yeah I did. A little bit flooded, yea. I noticed that temp sensor and aac valve plugs were swapped. I have one more thing in my mind that will try to address today and see what happens. I am also getting some misfiring when hot, so will try to check the injectors too / run some injector cleaner fluid before that.

[tatsurou]

Alright boys, fixed now! Turned out to be an array of things. The temp sensor I replaced was dead, and I thought it's working - checked it again this morning with a multimeter - resistance was stuck at 7.5k. Due to that it cracked a spark plug, hence the misfire, and also the IACV and Temp sensor plugs were plugged in wrong places. So three things at the same time caused an absolute nightmare. Thanks for help!

[pointz]

Glad you resolved it and thanks for posting what caused your problems

[R3K1355]

Hats off to Nissan for using the same plug for two completely different sensors, close to each other.