Slow crank issue

[stephenhughes]

Hi all, I have a 2007 mercedes saloon E280 CDI. When cold starting it takes 1 long attempt to start and sounds a bit slow cranking. After driving a few miles it starts first time and the cranking is a lot quicker. I tested the battery before an overnight start and it tested 11.5v after running the car a few miles the battery shows 12v on a tester. I've put the battery on charge after a 3 mile run after a cold start and it says 50% charged. Is this a battery issue or an injector problem on a cold start please. I've been told it's probably an injector problem by a mercedes specialist as it's common for a slow start. I've noticed the heater plug light stays on longer before a cold start but when warm goes off almost immediately.
Thanks ste

 

[alecmascot]

tested the battery before an overnight start and it tested 11.5v after running the car a few miles the battery shows 12v on a tester.

The battery is shot. It should be well over 12v after standing all night.
When the egine is running you should see 14.4v or the alternator is suspect. It's probably the brushes.

 

[markmifsud]

at 11.5v your battery is almost dead, hence the slow crank speed.

At reast it should really be at least 12.5. Put your meter on the battery with the car running, it should show around 13.5v to 14.3v. If this is the case then your charging system seems to be OK, if not then perhaps the battery isnt ever getting fully charged, but I would sustpect the battery

 

[W1ghty]

What is the battery date on the terminal ? But either way , as above it’s had it at those volts

 

[TeddyRuxpin]

Glow plug relay module if not battery

 

[stephenhughes]

Thankyou everyone, I'll update after I've charged the battery up and see if it cranks and starts as normal

 

[W1ghty]

Thankyou everyone, I'll update after I've charged the battery up and see if it cranks and starts as normal

If it’s the original gp relay it’s probably worth changing at some point anyway , my E320cdi struggled with slow start a couple of years or so ago , as part of bringing it up to date I changed the battery , plugs and relay . It has started on the button since

 

[johnsco]

Thankyou everyone, I'll update after I've charged the battery up and see if it cranks and starts as normal

I think the message is that your battery is at the end of its life.
It needs mending with a new one.

 

[Petrol Pete]

Hello and welcome . Buy a good quality new battery . Winter is coming , you won't regret it.

 

[stephenhughes]

Morning all, it was my battery, after charging it up it was reading 12.7v, I have now ordered another one, thankyou very much to all of you who replied to my issue.

 

[alecmascot]

Morning all, it was my battery, after charging it up it was reading 12.7v, I have now ordered another one, thankyou very much to all of you who replied to my issue.

Are you getting 14.4v or so from the alternator when the engine is running ?