I will combine 2 threads into 1 to save space. Firstly, my car is hard to start when it's hot, seems to crank over abit slower, pulling spark plug number 1 shows it has spark (slightly weak) while cranking. Fuel pressure is good, PTU is a S2 (about 2 yrs old) and relocated to the side of the engine bay, no error codes when cranking. Starts ok when it's had time to cool down. It was on the dyno yesterday for 3 or 4 hours so the CAS was pretty hot by the end of it. Swapped to another CAS that we knew was working and still no luck. The car can be push started ok and ignition under load is good, making good power and no missfires on boost. I'll probably get a new CAS anyway to replace the 20yr old part but I don't think that's the problem. The tuner thinks it could be the starter motor getting hot near the dump pipe (there is plenty of clearance and I do have the heat shields on the starter motor). Could the current draw from the starter be higher when it gets warm/hot which reduces the spark? Is there anything else I could be checking? Some of you might know that myself and Chris converted my car from a NA to TT over the last few months (it took us about 7 weeks, working on it on weekends). We had it running about a month ago, and it finally hit the dyno yesterday. Some details: Engine was from Andrew in WA (ex PZP motor) http://www.aus300zx.com/forum/showthread.php?t=311074 . I've only added Z1 adjustable exh cam gears to this. Turbos: Z1 GT600R (GT28R), UAS OEM ported manis, 3" split dump (i think these are alloytoyz), czp AVS/ARC intercoolers. exhaust reduces to 2.5" after the dumps, into 2 metalcats, UAS centre muffler, magnaflow rear mufflers, blitz DSBC-R dual solenoid boost controller. fuel: sard 650CC in OEM rail. Turbosmart FPR1200 regulator and new OEM tt fuel pump. ignition: BKR7E copper spark plugs, gapped up to 1.0mm. near new S2 OEM coilpacks, S2 ptu. tuned by Trent at chequered tuning (aka Status tuning) using Nistune on a hub dyno. The tune isn't really finished yet, there is still more left in it. We haven't touched the Exh cam timing yet (still set to 0degrees). Trent says there is another 15-20kw if I replace the rear mufflers (I never really realised but the 4" tips on the magnaflows have a 1.5" reducer behind them which is really choking the flow, we measured the exh back pressure to double check). Haven't adjusted base fuel pressure either and I think we can still put more boost into it (it's on 19psi at the moment). I'm happy with the way the car drives at the moment, feels responsive and it should be even better when it's fully tuned.
Had a simi;lar situation with an Opel, would not fire if you cranked it but would push start evry time when hot. it was due to a bad earth to the motor . Try putting a jumper lead from the battery earth to the plenum area/motor and then try. Heated cables cause high resistance in cables. Good luck.
Have a look at your cranking voltage. Ive noticed that these things dont start well if the cranking voltages drop much below 10v. Even if they seem to wind over reliably. Its a fair call regarding the starter. Heat certainly can affect the starter and if its a "lazy" starter to begin with then this compounds the problem. I suspect the cranking voltage readings, both hot and cold, will reveal something. l8r E
also if your battery terminals are corroded or contact is poor heat again increases resistance and can prevent sufficient cranking amps being drawn
Nice work I'm also about to finish a TT swap on mine. What's the specs of the motor and heads? Another quick question regarding your a/c what did you do with the hardlines could you bend the n/a ones to take the TT condenser and turbo pipeing?
your power chart stops at 5800rpm why? detonation or spark blowing out 1.0 is way to big . you should be looking at 0.8 / 0.7 maximum also hard starting when hot can be caused by fuel leaks, a faulty cas or poor cold/hot start timing enrichment
Check your ECU water temp sensor (2 pin plug) when the terminals corrode, the ECU gets an engine cold reading and overfuels for a cold start but because it's warm or hot, it soaks the plugs... Good luck! Sam
Thanks, will try running some more grounds off the battery and see if that helps. I've just checked cranking voltage when hot. Battery was at 13.7V, dropping to 11.5-11.7V when cranking (seems to be cranking over at normal speed but still no start). I'll check the cold cranking voltage later today or tomorrow morning. thanks, Will clean batter terminals and have another go. thanks, specs on the motor are in the link in first post. I found someone selling all the TT A/C stuff so used that. my understanding is that you should use the biggest spark plug gap you can get away with without blowing out spark on boost. the car doesn't misfire on boost, the coilpacks are only a few years old. most people who have 20yr old coilpacks will need to drop the plug gap since it can't jump the larger gap on boost. the red line that stopped early was one where the tuner backed out early. i don't think it's fuel injector leaks, will try the cas. on the dyno we tried to restart the car on the car's original run in tune but no luck but that might have the same hot start issue as the new tune. I'll give this a shot tomorrow, I checked it a few weeks back using datascan and it follows the external temp gauge i've got so I think it should still be ok. thanks chad, how is your car going?
update: have tried a few things - new/more grounds off the battery, didn't really make any difference. - another battery (made starting a bit easier, old one was struggling) - another CAS, no change - coolant temp sensor checked ok, temp is same as my other gauge have noticed that if you give the car a bit of throttle while cranking it starts easily, hot or cold. without throttle it struggles when hot but will start (not as easily as when you give it throttle). where does the engine get air while trying to start (with the throttle closed)? is it through the IACV or do i need to look at how my throttle bodies are adjusted?
I just read that you say the coolant temp sensor is o.k because temp is the same as your other guage ?. This makes me believe that you are checking the wrong sensor as the guage operates off the single wire sensor which is a different sensor to the 2 wire e.c.u sensor ( unless you are reading of e.c.u talk ? ). Cheers Dave
drop your plug gap down to. 7-.8 like simmo said. What heat range are your plugs. Check your plenum earths are good and maybe do a hot compression test And check your tps is set correct Edit sorry didn't read bkr7e plugs
any update yet .. i think your over fueling on startup even when hot . it starts when cold , because ecu is in cold start mode to much fuel presser will not help you in any case, check tps while ignition is on ( not engine running just ignition.) it need to be of ( on the consult ) , but when you tap your accelerator ( just a tap) it will turn on ( on/of will be seen on the bottom of consult). ( use consult ) tps setting 3.8 closed but at WOT 4.3, if you get 3.8 at (of) and you don't get over 4.3 at WOT , adjust the screw on the manifold in the middle of the T/B's make sure tps is OF on just ignition and on idle. your value may change . it might see 3.9 close it might see 4.0 close . max WOT should be good at 4.3 or 4.4 . check butterflies in T/b that they are both opening at the same time ( just a crack ) . you can see this without taking the front pipes of , if you do adjust your T/B you will have to do your tps again. once all done reset tps ( 5 or 10 seconds )then re check . if your still having problems bring it over.
