MHD intermittent starting problems

[Larsson]

Hello,

Just wanted to check if someone had any ideas on possible solutions to starting problems with the 451 MHD.

Whether hot or cold my smart has issues starting, sometimes I have to turn the key 2-3 times before it finally stumbles and fires up.
I get the feeling that the starter-alternator turns more slowly than usual and it has gotten worse over the last few weeks.
There are no issues with the alternator charging voltage.

• I have replaced the battery with a new AGM unit.
• No error codes presented.
• Checked and cleaned battery and starter connections / cables.
• The Poly V-belt is new and not slipping.

Anyone have a suggestion before I take the engine out and replace the rather expensive Valeo alternator-starter unit?

Thanks in advance!

/Alex

[Thrumbleux]

[*]I have replaced the battery with a new AGM unit.

Straightforward replacement or with some other (eg, coding) work?

Don't know if it applies to MHDs or not (it's more a stop/start system than actual hybrid) but some hybrids require some dealer recoding when a battery is replaced. The charging rate alters over the battery's life (intended) and needs to be recalibrated for the new one apparently.

[Larsson]

The ECU was reset prior to installing the replacement battery, charging voltage seems OK but I haven't measured the current.

[Thrumbleux]

.

Whether hot or cold my smart has issues starting, sometimes I have to turn the key 2-3 times before it finally stumbles and fires up.
I get the feeling that the starter-alternator turns more slowly than usual and it has gotten worse over the last few weeks.

Forgive me if I've got it wrong, but I thought the MHD started with conventional starter motor from cold, the combined alt/starter only being deployed when/if the engine is at operating temperature. If so, then either both starter motors are failing it or the problem lies elsewhere eg, duff ignition components, stale fuel, etc.
Any misfires under load point to ignition failings. In this case though, is it not exhibiting the signs of a failing cam position sensor? - but without codes.

[Larsson]

The MHD only have the belt driven alt/starter unit. The curious thing is that it runs great when it eventually starts, spark plugs where recently replaced as well and the emission values are good.
I will check the cam pos sensor. Thanks.

[Thrumbleux]

I think there are some recent threads on this forum re cam position sensors.