Slow starting.

DaveEFI · Post by **DaveEFI** » Sun May 31, 2015 11:27 am

My SD1 3.5 is a bit slower to start than I'd like. Takes about 5 seconds of churning. Then starts and idles just fine.
Running an MS2 and EDIS. A log when starting shows it is seeing a tach signal as soon as the engine turns over (by the battery volts dropping) so it's not that.

I've a feeling it is something to do with fuel evaporation when parked up.

If I do a cold start then stop the engine - not something I like to do - it will then start much more quickly the next day from cold. But of course the norm is it is fully hot when stopping the night before.

I've tried running the pump for much longer than the MS priming second or so before attempting a start to make sure there is actual petrol at the injectors, but it makes no difference.

Anything I'm missing? Could there still be 'air' in the fuel rail even with prolonged running of the pump?

DEVONMAN · Post by **DEVONMAN** » Sun May 31, 2015 12:00 pm

Is it possible to make the cold start setting a little richer with the MS.

Worth a try.

Regards Denis

DaveEFI · Post by **DaveEFI** » Sun May 31, 2015 12:30 pm

DEVONMAN wrote:Is it possible to make the cold start setting a little richer with the MS.

Worth a try.

Regards Denis

Oh yes. You can alter the priming pulse (squirt at switch on to clear air from the rail) cranking pulse width and after start enrichment. I'm fairly certain these are all (near) optimal having played with them over the years. When it does 'catch' it does so instantly. If the cranking fuelling was wrong I'd expect it falter slightly?

It's also much the same on a very cold - or mild - day.

stevieturbo · Post by **stevieturbo** » Sun May 31, 2015 4:02 pm

The chances of it being heat or fuel rails etc...is almost zero.

Run the engine til warm and remove all starting enrichments.

Then add enrichments until it starts quickly. Also ensure the engine has sufficient air to start, so if using any sort of air bypass make sure it is open enough to allow starting ( assuming throttle blade may be closed )

But yes most engines will like an initial squirt of fuel to the engine over and above normal cranking enrichment for easy starting.
But it wont matter how much fuel you dump in, if the engine hasnt got any air.

DaveEFI · Post by **DaveEFI** » Sun May 31, 2015 5:48 pm

It has the standard SD1 EFI extra air valve. That is bi-metal so opens entirely with temperature. Fast idle is what I'd expect.

Last time I played with increasing the cranking pulsewidth, it was worse.

stevieturbo · Post by **stevieturbo** » Sun May 31, 2015 6:15 pm

DaveEFI wrote:It has the standard SD1 EFI extra air valve. That is bi-metal so opens entirely with temperature. Fast idle is what I'd expect.

Last time I played with increasing the cranking pulsewidth, it was worse.

Increasing from what though ?

As I said, start with zero enrichment. That way there is only one way to go when testing.

A hot engine really should need little additional help to start.

DaveEFI · Post by **DaveEFI** » Tue Jun 02, 2015 9:45 am

As I said I've played with the cranking pulse width enough over the years to be fairly certain it's as close as makes no difference. It's also much the same as others use on a standard Vitesse unit.

Did you read the bit that if you stop the engine before it warms up, it will then start much more quickly on the next cold start - even if that is the next day or longer?

FWIW, it was never an instant starter even with the standard injection and ignition.

Must admit to wondering about the fuel rail design. On the flapper, it is a ring. On the later hotwire, larger diameter with an in and out at either end - no ring. So I'm wondering if 'air' gets trapped somewhere.
Other difference too is I no longer have a cold start injector.

stevieturbo · Post by **stevieturbo** » Tue Jun 02, 2015 11:15 am

I would never go by what others are doing, I go by what each engine wants.

IMO if it's taking 5 seconds to start, something is very wrong.

I'm not saying you'll always get an instant start same as OEM, as they go to great lengths to get that again for emissions reasons.

But it should easily start within 1-2 seconds...not that a few seconds cranking is a bad thing either as it can get oil circulating.

As for air in the rails, I just cant see it.

I've had my primary injectors both in dead end rails for several years and never had starting problems hot or cold.
An initial key on pulse, or initial cranking pulse should easily expel any air in milliseconds, if air somehow got in there.

If playing with the various settings doesnt get it working, there may be some sort of trigger issue, or as said the engine simply needs more air during cranking.

DaveEFI · Post by **DaveEFI** » Tue Jun 02, 2015 11:59 am

I didn't go by what others used. Arrived at my own settings. But have seen what others have arrived at too.

The very first thing I'd check anyway is that MS is seeing a tach signal as soon as possible when cranking commences. As it won't inject without one.

And it is - a log shows the tach signal present as soon as the battery volts drop under the influence of the starter.