T6 Sluggish / slow start

[Jenky212]

Hi there, 2018 t6 with 64k miles it has a sluggish start, more notable 1st start but is always abit sluggish. It turns over as if the battery is low, turns a couple of times slow then fires right up. It’s got a new battery, which is testing good with a battery tester. I’ve tested volt drop on positive and earth cables which is ok. I’ve checked current draw on starter cable which is around 200-250 which I think is ok, but this might be the problem the 2nd smaller positive cable off the battery battery has about 500amps draw so both cables together is 700-750 which is as much as the battery. could anyone please check theirs and see what theirs is drawing on start up or if anyone has any advise it would be greatly appreciated. Many thanks

 

[mmi]

I’ve checked current draw on starter cable which is around 200-250 which I think is ok, but this might be the problem the 2nd smaller positive cable off the battery battery has about 500amps draw so both cables together is 700-750

For how long? Average of 3 seconds, or just a peak for a microsecond?

Post in thread 'Which Jump Starter?'

21 Oct 2018

And off course jump starting.... now needed it on our vans yet.... but used numerous times to help out others.

So that's in the real world. But in theory?

T6 diesel engine start-up

Measurements were done using a VCDS cable, achieved time resolution 130 ms.​

Timeline of events :

• Timestamp 3.5 sec: Initiate starting by turning key to position start
  
  Preglow, power up of ECU+other modules, lights, etc​
• Timestamp 5.2 – 6.0 sec Engine cranking, drain from battery peaks at 400 A for 0.3 sec
  
  Afterglow​
  ...

• mmi

• 

 

[Dellmassive]

Got a video clip of it starting?

Drop it on YouTube, it a link to your online album here.

What can spec?

Is it using oil?

Slow start could be,

Poor battery health,
Corroded main engine Earth,
Poor glow plug heating,
Dirty injectors,
Low fuel rail pressure,
Leaking injector,
Etc etc etc

 

[Jenky212]

the numbers are peak using an amps clamp on the cables on the first cranks of the engine. I would have thought 500amp is a lot for the smaller cable but don’t know what runs of that circuit. I thought 200-250 amp on the starter cable was ok? So don’t think it’s the starter. But 700-750 amps is nearly double your graph which is why I’m guessing I have a slow start.

I will try and get video up loaded
In regards to oil, it’s genuine oil and does not use any.
All starter wires/engine earths ok as no volt drop
Injectors glow plugs ect no fault codes, and it doesn’t turn over for a long periods before it starts, it just turns over very slowly, but starts after about 2-3turns

 

[mmi]

the numbers are peak using an amps clamp on the cables

What's the make/model of the clamp? Asking because it's essential to know the clamps peak measurement time because the measurement in this case is a transient current for a stationary electic motor - which is essentially a short circuit. To get more "meaningful" figure need to "average" for 100 ms or so (my graph used 130 ms integration/averaging time). Many current clamps can use as low as 1 ms for capturing transients.

700-750 which is as much as the battery. could

(Cold) Cranking Amps CCA/CA on battery label is specification for 30 seconds draw. They do much more

I would have thought 500amp is a lot for the smaller cable but don’t know what runs of that circuit.

The thicker 35 mm² cable is the starter alone. The 25 mm² is for the rest of the van's electrics so during cranking mainly glow-plugs and ECU.

I thought 200-250 amp on the starter cable was ok? So don’t think it’s the starter.

Well, we possibly are not comparing apples to apples with you 200-250 Amps and my graph. Unfortunately I don't have a gadget to capture such a huge currents at very high rate to compare.

I would try to measure the current when engine is cranking - the 200-250 Amps possibly as in-rush current doesn't seem to be a lot.

 

[andymcvw1]

Probably a just a lazy starter. It'll die suddenly.

 

[Jenky212]

What's the make/model of the clamp?

It’s a Lucas ywb233 amps clamp. I don’t see how any ecus relays ect should pull 500amps combined on that smaller wire. I’m going to try and test another van if I can fine one.

Probably a just a lazy starter. It'll die suddenly.

That could be my next port of call if I can’t test another van to just eliminate it.

 

[mmi]

t’s a Lucas ywb233 amps clamp.

Interestingly Google can't find anything relevant.