X trail hard to start when cold. Out of ideas :(

On 08/02/2014 19:53, Tim

Main earth strap has already been changed, it runs from battery to chassis and then onto the engine..

9v at the battery terminals themselves (and the same across the clamps, which are clean and tight) and 8.5v at the ECM main power terminals when cranking, this is with yet another new battery. (ECM voltage is 11.5 when not cranking and 14.4 when the engine is running - measured with a (trusted) DMM at the ECM power relay adjacent to the ECM) Starter has been examined by a local specialist and pronounced fit, not surprised since both starters do exactly the same thing... Engine doesn't feel excessively 'tight' when turning by hand, (feels the same as the other one) and when it cranks it is at a fairly even speed.

It seems completely obvious that it is the starter, but the one which works perfectly on the comparison vehicle still exhibits the same symptoms on this one.

What is Battery or ECU feed voltage doing during cranking, and also -ve verses battery -ve on the block and at ecu? Is the ECU ground good? Obviously the current draw of the starter is upsetting something.

I would be 'scoping the battery feed under cranking to see if a dodgy starter is spiking the ecu with EMF, or the rail pressure sensor signal line.

IME, a problem with the suction valves creates a bad rattle, lack of power and copious blue smoke, rather than a no-start.

Tim..

Autodata says it has, but it hasn't. The Nissan service manual shows an external "fuel transport pump" which pumps fuel between the two U-shaped sections of the tank. It's not easy to get at but I guess I should eliminate that as well, even though it should in theory have no bearing on the problem.

On 22/02/2014 17:13, Tim What is Battery or ECU feed voltage doing during cranking, and also -ve

The voltage at the ECM power relay is 8.5v when cranking,(9v at batt)

11.5 (11.9 at batt) in Ign on, engine off and 14.4v (14.4 at batt) with engine running. About the same as the ECM reports over ODB.

Not sure where it's dropping that 0.5v, if you run a thick patch cable from the battery to the relay then the 0.5v drop disappears but it doesn't make any difference to the behaviour. ECM ground is good, it's bolted directly to the chassis anyway. DC waveform at the ECM is a little spikey when cranking, but it doesn't look any worse to me than other vehicles I've checked. Maybe this one is more sensitive - I'll have to think about decoupling it with something suitable.

why not leave the onboard battery to run the ecu and connect a spare battery directly to run the starter, if it is then starting and running ok then you will know it is a power problem

Exactly what I was going to try, later :)

Lee

I was about to say the same thing. 8.5v at the ecu is just not enough. It needs to generate ~80v to fire the injectors...

Power the ECU directly from a separate battery via some good quality jump leads / patch cable and try again.

Tim..

replying to Lee, Mmeldrum29 wrote: Hi. Did u get to the bottom of this problem. I imagine having exact same symptoms with mine

Yes, but the actual final cause will certainly not be relevant to your issue. (it was an incorrect part than had been previously fitted)

Obviously you need to have checked all all the usual suspects, ie injectors/temp sensors/maf/ crank and cam sensors etc

Wear in the chain can cause poor cold starting (as I found out)

What I found useful was viewing the timing correlation of the crankshaft and camshaft sensors on a 2 channel oscilloscope. The correlation varied too much between hot and cold and pointed to the (new) chain being badly out of spec.

What problem? The crap web site you are using links your question into a post about gear changing problem on a fiat punto that was posted 12 years ago!