K11 Starting Issues - Ideas Appreciated!

[AdamR]

Morning all,

New to Micras but not new to tinkering with cars! Already had a good look around the forum and found some really useful info, thank you - it's a brilliant resource.

Anyway, I picked up a 1.0 K11 (2001, coil-on-plug version) Micra last week and been gradually going over it sorting a few bits. The car has done ~19,000 miles and still has 3 of the original tyres on it (new ones been ordered!), plus the original aux and alternator belts (now been swapped), and came with a free indoor swimming pool (now been drained).

It looks to have had reasonable use in the last few years (~6k miles in the last 2 years) but had been stood for a bit before I picked it up. Despite this it fired into life perfectly first time, ran beautifully, and subsequently did so for the next half a dozen times - but wasn't warmed up fully after doing so, so I assumed it had the 'cold flooding' issue.

I pulled the plugs out to find they were sopping wet, so left them out over the weekend. Battery is good (holding a solid 12.5v and cranks the engine nicely), I've fitted a new fuel filter (which is the right way round ), treated it to half a tank of V-Power, and it's been cranked quite a bit with the plugs out and fuel pump fuse pulled to prime the oil and fuel system (edit - just realised that won't be priming the fuel system then will it, ha! Perhaps it just needs more cranking to get fuel to the injectors). I also hoped this would get rid of some of the excess fuel in the cylinders.

The immobiliser light on the dash flashes as normal when ignition is turned off, with the ignition on and the car cranking it goes it - which I assume is normal.

I had soldered a resistor in parallel with the ECU water temp sensor to try and prevent the cold start problems in future, but in case this was cocking things up I have subsequently removed it to return things back to standard.

Trouble I'm having is that the little bugger won't start. As I've said it cranks well, and appears to be getting fuel (the new plugs have got wet too). I need to enlist the help of a friend to check for spark (the coil sticks are 'spring loaded' so the plugs fall out if you're not holding them in), but other than that I am out of ideas.

Anything else I should be checking?

Thanks in advance!
Adam

 

[vexorg]

Have you checked the plugs are sparking?

 

[AdamR]

Thanks - I've now had chance to do that, yep. Nice strong spark.

... and it runs! I just needed to crank it for longer with the throttle fully depressed, it then started to cough and splutter into life. Obviously it died once the unburnt fuel had been used up, but after sticking the 15A fuel pump fuse back in, all was well. Plenty of white smoke initially but that's now gone.

So I guess the moral of the story is... just keep trying Thanks again.

Time to bodge that resistor back in to try and prevent this from happening again...

 

[MattInARedMicra]

They do flood, typically happens when you start it and turn it off without driving it anywhere (or only moving it a short distance like moving carparking spaces) and then leave it overnight in winter

To get it going again you did the right thing, pull the fuel pump fuse, turn it over for a minute, leave it alone for an hour or so, maybe charge the battery if it's been standing for a while or use a jumpstart pack to give the battery some extra cold cranking amps, then fuel pump fuse back in and keep cranking until it starts, once it does give it some revs to clear everything through

I've had this happen twice, I stopped doing journeys shorter than a mile now in winter, just not worth the risk that I'll be stood outside stranded in the cold. If I have to repark it I'll drive around for 10 minutes and come back and then let it idle for 30 seconds before shutting it off.

 

[AdamR]

Thanks for confirming my thoughts Matt!


I ended up putting a 7.5k resistor in parallel with the ECU temp sender to try and stop this happening again. I know the official Nissan fix is 15k, but I had read others sticking a second sensor in the loop (which would read around 2.5k at 10 degrees C) so figured anywhere in between those two would work...

Looking at the graphs in Paul / @pollyp 's thread it looks like a 7.5k will fool the ECU into thinking it's about 10 degrees warmer at startup (ie. ECU thinks it's 20 degrees when it's actually 10), and make virtually no difference when the car is fully warmed up: https://www.micra.org.uk/threads/pollymobiles-rebuild.35251/page-119#post-704079

With the standard sensor reading 2.5k at 10 degrees C, with a 7.5k across it in parallel that will then be 1.875k, and thus the ECU will 'see' ~20 degrees. The Nissan 15k resistor would make the car see around 17 degrees, and a second temp sender around 35 degrees C.

Fully warmed up the difference is really minimal - 0.3k Ohms at 90 degrees C becomes 0.288k with the 7.5k resistor in there, so the ECU will see something like 92 degrees. Guess the fan may come on a few degrees earlier than standard, but I can live with that.

Depends exactly how Nissan have mapped the cold start enrichment, but based upon previous experience I would estimate it's putting 10-20% less fuel in now. So we'll see if that does the job - should do if the Nissan 'fix' worked! It certainly still starts, idles and runs perfectly at all temperatures so far.

Got a few other bits on the car done today and got tax and insurance sorted out so I could finally drive it - surprisingly nippy at lower speeds considering the modest power output, and it's a nice place to be. Love how the little engine gets more and more perky the closer to the limiter it gets!

Perhaps needs a couple of handling tweaks asap as it is a little understeery right now, and I plan to take it to Oulton Park on Saturday