Sports: Re: {Disarmed} [DucatiST] ST4s Wont start

The fuel pump should turn on for about 3 seconds at switch on to pressurise the fuel line. If it doesn't do so the relay is the most likely culprit. However, for the engine to run, even briefly, there has to be some pressure in the line which suggests the switch on priming is occurring.

When the engine is turning, either on the starter or by self-propulsion, the crank position sensor (rpm sensor or engine position sensor, whatever you want to call it) sends pulses to the ECU. On sensing these pulses the ECU switches the pump relay back on and keeps it on as long as the engine is turning. It also uses the pulses to work out the spark and injector timing.

So, if the CPS fails the pump won't turn back and stay on to keep the engine running. The trouble with this diagnosis that if the CPS fails there is usually no spark nor injection either. I wouldn't rule it out though.

Derek
'03 ST4s abs
Scotland

From: Nick Vale <nickvale@bettertest.co.uk>
Reply-To: st2_owners <st2_owners@yahoogroups.com>
Date: Thu, 07 Apr 2011 09:43:06 +0100
To: st2_owners <st2_owners@yahoogroups.com>
Subject: Re: {Disarmed} [DucatiST] ST4s Wont start - Any ideas?

Fuel pump relay perhaps - did you get the fuel pump hum when turning on? If not try switching the two relays under the seat (the other is the fan, so not as crucial). Any other symptoms? Otherwise might be the dodgy ecu problem - other people here have suffered it in the past, I'm sure they'll be able to provide more info

Cheers - Nick

See the face, admire the bikes, yawn at the holiday snaps...  http://www.worldwidewobble.com

On 07/04/2011 08:27, Paul wrote:

Out on it today and all well, stopped at a mates for a coffee and it turns over then starts/catches for half a second and then dies and repeats this until battery flat. It had fuel and battery was OK. On centre stand so not sidestand cutout.

What would allow it to almost start and then stop?

All suggestions welcome.

Paul

UK.

No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1209 / Virus Database: 1500/3553 - Release Date: 04/05/11