Extended cranking time cold start

[blitzracing]

The big thing here is it fires on Easy start (or like) straight away that would discount anything nasty mechanically. The thing about the HT voltage is it only rises until the arc starts- as this is effectively a short circuit at the plug tip once the arc is burning. So if you have an HT coil with its output in free air, the voltage will keep rising to typically about 30kv as there is no arc. Same will happen if you have HT leads with breaks in them, or plug extenders that are faulty- the voltage has to rise to a point it can overcome the break and ignite the spark. In a good system you wont see the HT rise that far as it only takes 5-15 k to jump the plug gap and start the arc. This diagram shows it quite nicely- voltage rises to 14kv- arc starts and the burns at 3kv

Edited by blitzracing on Sunday 13th May 20:44

[Ozstyle]

So checked spark plugs, all good, gap right, no heavy deposits on electrodes, colour fine as expected.
Cleaned stepper motor and housing, but as expected clean anyway.
Checked base idle, little high, adjusted down.
Absolutely no change still extended cranking when fired from cold.

I have not checked compression in recent times, but as it fires with just 1 squirt of starter fluid at present I'm ruling this out.
Car runs absolutely spot on, no stalling, no hesitation or misfire at any speed, accelerating or decelerating, idles fine.

I still have not tried my spare ECU will try this weekend.
I'll also check ohms across each injector bank at ECU plug

[Ozstyle]

so,
changed the ECU coolant temp sensor for my spare good one,
reset ECU by disconnecting battery for 5 minutes,
checked ignition timing, bumped up a degree as touch retarded.
gave the battery, which is good, a full trickle charge for 5 hours

engine spins over like a top, but no change still extended cranking time from cold, 6+ seconds before it splutters into life

one thing I have noticed if I turn over for a couple of seconds, stop wait a couple of seconds and turn over again, straight away it splutters into life, just thinking this may be giving time for any fuel droplets in the system to vaporise

still not tried my spare ECU yet

[Ozstyle]

just to close this thread off,
the extended cranking has resolved itself,
no idea what the issues was, all that I did since the problem occurred was add a bottle of fuel injector cleaner, a couple of long runs (2+ hours) and a few tanks of fuel . Assumed I just had some crap fuel causing the issue, but who knows. Cranking time back to about 2 seconds before it fires.

[David Beer]

Ozstyle said:

just to close this thread off,
the extended cranking has resolved itself,
no idea what the issues was, all that I did since the problem occurred was add a bottle of fuel injector cleaner, a couple of long runs (2+ hours) and a few tanks of fuel . Assumed I just had some crap fuel causing the issue, but who knows. Cranking time back to about 2 seconds before it fires.

My mower was a devil to start after the winter lay up, told by the service people, petrol only lasts 3 months . The ethanol separates, becomes a thick gunge at the bottom of the tank. Now mix with a additive to stop it. Maybe !