Hot Start Issue

[Hanaldo]

Hey all,

I did a bit of a search but couldn't find anything similar to my issue.

The problem: When I crank the car after the engine has been running for a bit, it doesn't really want to fire. Sometimes it will crank for a bit longer than usual and then fire, sometimes it will crank and I can hear it trying to fire but it dies if I don't give it some throttle, other times it will just crank and crank and crank and refuse to fire even if I give it throttle, and sometimes it just starts normally. There is no problem at all on cold start, it always fires instantly when I turn the key.

The background: I've had a slight hot start problem ever since I had my injectors (and turbo, but that seems unlikely to be related) installed and the car retuned. However it was never so bad that it refused to fire or required any throttle, it just made a strange sound when I cranked it and took a bit longer to start than it did when cold. It has since gotten worse after I relocated my battery to the boot, though I'm not sure if it is likely to be related or not. I had it at my tuner last week trying to sort out another issue, and I did ask him to take a look at the hot start but he said when he tried to have a look it fired normally so wasn't sure what the issue was.

The question: My first guess is that this is most likely the hot start mixtures? Is there anything else it could be, eg. electrical problem or failing sensor?

[GTRNUR]

What kind of ecu are you using?

Have a look at your starting ignition values. RB's like up to 45 degrees ignition advance for cranking.

All ecu's work a little differently, but cranking ignition (below 300 RPM or so) should be 45 advanced, after which it will switch to the base ignition map + corrections for temp etc. Its not needed when its cold (15 degrees will do), but definatly is needed when the engine is hot and heat soaked.

Sometimes a little extra fuel in the cranking values for the hot temp (80 degrees area), will also help wet the manifold and prevent a momentary lean condition after starting.... Again different ecu's different startup options...

[Hanaldo]

Using NIStune...

[SiR_RB]

had the exact same problem with my car, running nistune too

had abit of fuel taken out of the hot start mixtures and all is good now

before that was done i changed fuel regs, air temp sensor, coolant temp sensor, battery etc lol

[STATUS]

sometimes the temp comp gets a bit screwy on them during (maybe 1%) read and writing and it it may have been overlooked sometimes the values go to 255, just do a compare against the values and the std binary.

[Hanaldo]

Ok so I'm still waiting on my users license for the NIStune software, unfortunately someone removed the part number sticker on my ECU so it's a pain the ass to get the license.

But, I just went and filmed this video of my car:

http://www.youtube.com/embed/Kvt3O58w_Ak

This is not even the worst it has been, sometimes it will just do this over and over and over and I can sit there for 10 minutes and it just won't start. And randomly, I actually started the car just before I filmed this video and it started first shot, no issue.

Does the video change anyone's opinion of what the issue could be?

*EDIT* damn thing won't embed

Edited August 29, 2011 by Hanaldo

[Hanaldo]

Should also mention this video was taken after the car had been sitting for about 2 hours. You can see at the start of the video, the water temp gauge (on the left) was showing about 60 degrees and the oil temp was below 40. So it's not HOT hot, but it's still a bit warm. When I start the car for the first time after it has been sitting all night (so fully cooled off) it will start as soon as I turn the key.

[femno]

Cranking injector ms values.

Also if you used cable too thin for the battery relo that will make it crank slower, and higher initial starter motor in rush current could even starve the ecu of the voltage it needs to operate, therefore harder to start.

[Room42]

I tried changing injector lag time, cranking ms again, ignition dwell, timing in the cranking cell, fuel in the cranking cell. None of it had a huge difference really. I watched a chart of the injector duty cycle whilst turning the key to start it and it basically went on a gentle slope till it started. Even when adding lots of fuel to the cranking ms all it did was a slope then a spike before settling on 1% duty cycle at idle. Changing the dwell a little bit just made it start with less of a rev and less misfiring. My car used to crank for 3 seconds or so when it was at its worst and now it starts a lot quicker. It would make sense that the injectors would be doing what they are told immediately rather than there being a slope in the duty cycle chart....My lag time was advertised as 0.058. I have it at 0.08 now and it idled richer and started better. I wonder if a new battery is in order tho? I have noticed rather high voltages being shown. That is usually a sign of a stuffed battery.

[Hanaldo]

Cranking injector ms values.

Also if you used cable too thin for the battery relo that will make it crank slower, and higher initial starter motor in rush current could even starve the ecu of the voltage it needs to operate, therefore harder to start.

Yeh I used 00 (or -1 if you prefer) gauge wire, it should be plenty thick for that distance and amperage.

[wolverine]

The stagea is prone to being hard to start and it has had a PowerFC and now has Nistune. So I don't think it is necessarily a Nistune based issue.

[Hanaldo]

Right, I got my key-code from Matt today, so I can start using the NIStune software.

I'm slowly reading through all the documentation to learn how to use the software properly, but this problem has become a huge headache and I was hoping to sort it out asap. I've synced my image on the ECU with my laptop, so I've spent a good hour or so looking around trying to familiarize myself, but am still a bit lost. Could anyone tell me where I can find the things I should be checking on NIStune? And what their values should be? I tried comparing my image with the base R34 image, but there's a number of base images that came with NIStune so I'm not sure which one to use.

For example, GTRNUR said to check the cranking ignition values. In NIStune, I'm guessing this would be the Cranking Timing Advance BTDC? I had a look at that and it is set to 10 degrees (timing) up until 90 degrees (temp), then at 100 degrees it drops down to 8 and 110 is 6, etc. Is that correct?

As for the enrichment tables, which of those should I be looking at?

[GTRNUR]

I honestly dont have a clue about the Nistune. I would be listening very closely to what Trent (Status) says about fuel temp compensations.

For all I know the ignition settings you are looking at may be corrections applied to a base figure that you havent found or can't change, they might not be the actual values that represent delivered ignition advance when cranking.

What I said before still stands though, and for hot starts especially. 40-45 degrees ignition advance when cranking (RPM below 300). Then when it fires it switches to the ignition base map value between 15-20 degrees from 300Rpm to 950 at idle. An RB will still start with 10 degrees ignition when its cold, but it is a lot harder to get it to start when its hot and heat soaked with that same ignition advance.

You could check your cranking ignition values by measuring and marking additional timing marks on your balancer with a white paint pen or liquid paper, and checking the ignition with a timing light with the injectors all unplugged. Have someone else crank the engine while you watch the strobe on the balancer.

Also having a wideband AFR meter plugged into your exhaust will give you some idea as to if it is fuel or not. When it does start (or tries to start) if it is immediately lean you would be inclined to think that its not enough fuel. Which could be temp compensation for the current engine temps affecting cranking values, or the cranking fuel values directly. Typically an engine responds well after starting with an AFR in the high 13's.

As you can see its getting complicated at this point and requires some tools you may not have. So if any of this is beyond your understanding or capability, having a professional look at the car is your best bet to a fast solution.

[Hanaldo]

Yeh, have tried to get it looked at but of course the car behaved when it was there. I don't exactly live close to my tuner, and he is always extremely busy so If I can work out how to fix it myself then it would be the easiest option. If I can't work it out then I'll have to take it back to him, but I might as well give it a go.

My wideband kit should be arriving in the mail any day now, so I'll get that installed as well. I could use my mates timing light as well, but that's probably getting too difficult. If it's not something I can correct in the tune then I'll get it looked at professionally.

Thanks for your help mate.

[Hanaldo]

You know what's really f**king awesome? Getting stuck at a petrol station 100kms away from home because your f**king car won't start. I love this shit, it's becoming a favorite past time of mine.

[bubba]

[GTRNUR]

If you happen to still be there and are stuck, try unplugging your coil pack loom. Then crank it for 5 seconds, then plug it in again and try to start it again. In theory this may wet your intake manifold enough to get it to start, that is provided the issue is that your still staving for fuel when its hot.

Or get a can of aerostart and spray it into your intake when someone else is cranking. It will take a bit to get that to work though as it really needs to go into the engine at the throttle body. I don't know if it will even work to be honest. Ive never tried it.

[Hanaldo]

Thanks mate, gave those a go but still not starting. Will have to wait a few hours for it to cool down I guess.

[SiR_RB]

This is how i got it started when I got stick somewhere before I fixed the problem

Take out fuel pump fuse, crank car, it should go to start but cough and die, then put the fuse back in and restart the car...should start

[GTRNUR]

One other idea is to unplug the coolant temp sensor, which is the 2 wire sensor on the pipe that is connected to your top radiator hose. With after market ecu's this will send the ecu to an off-scale temperature, so it thinks it is starting in a sub zero climate.

If it works, and starts, then plug it back in again once its running again.

Never tried that with a nistune or even a stock ecu for that matter though...