re #447 starting cranking problems

[leigh]

Hi, Iam a new subscriber to DIY_EFI and have read with great
interest the last couple of issues.
First off internal combustion petrol engines use atomised fuel not vapour.
Vapour is whats left in the tank when you run out of petrol. The
terminoligy of COLD/HOT starts is techincally Incorrect but most people no
that COLD is ambiant temp which can change drastically from locations
		 and HOT is operting temp ie aprox 85 to 100 C
on late model high pressure cooling systems. I think we get
blinded by technology to ofter and forget the basics.
As far as start / crank injection timing goes you need to set paramters for
varied ambiant & coolant temps. Most
factory systems fire one block of all injectors on the first crank pulse
then consective pulses while engine speed is below a predeturmand leval.
This pulse can be changed large amounts ie between 4ms to 20 + ms depending
on air & coolant temprature, cold, warm or hot start.
On a rpm signal above the predturmand leval they then switch to idle run
fuel blocks and muck lower pulse rates.
I have had recent experiance with a engine that had hot
start problemsdue to the ecu not returning to start mode
and only pulsing injectors for 5 ms, idle volume, when the fuel hit the
valve head it vapourized and would not start.
The pulse timing for hot start should have been around
15 ms.
Iam still waiting for the injectors flow rate to work out
the fuel volume per cyliner size to get a base start line.
 
regards    Leigh Turner