Caterham 7 K series starting problem

[Sumpplug]

I've owned my Caterham 7 for about a year now, its a K series R300 with roller barrel throttle bodies. It's always been difficult to start from cold. It'll take three attempts before it fires then it runs really rough. If you try and blip the throttle it'll die instantly and then won't start at all until it's been left for about an hour. If you let it splutter for about 15 seconds then blip it the engine will clear and run normally. The number 4 spark plug is always black but the other three are normal. It'll coke up after as little as 15 miles of normal driving.

I thought I might have a leaking injector that was flooding the cylinder but I've pulled them out and had them bench tested by a specialist and I've been told they are fine. Any other K series owners experienced anything similar?

[Rozzers]

Assuming you’ve a reliable spark - have these got 4 coil packs?- it might be the ECU that initially is sending garbage pulses to the injector until it gets going and the voltage comes up.

[Krikkit]

Rozzers said:

Assuming you’ve a reliable spark - have these got 4 coil packs?- it might be the ECU that initially is sending garbage pulses to the injector until it gets going and the voltage comes up.

Agree with this, either sounds like a bad coil (swap them to other cylinders if you can) or garbage from the ECU on cold start.

[Sumpplug]

Thanks for the replies. It's a 2005 car and I don't think it's got coil packs, just the usual H/T leads. I'll double check Thanks

[Thomasaspin]

Hi mate it does have a coil pack it has two coil packs and two ht leads sounds like there’s a fueling issue , could be a dodgy remap ?

[DVandrews]

I would also check the balance of the TBs, they should be drawing around 5,5kg/hr on each barrel, if the rear one is drawing less air then the rear two cylinders will be rich, this will be exacerbated when cold. If you have the means I would also check the throttle pot alignment.

Dave

[Sumpplug]

Thanks for everyone who chipped in. Dave was right on the money. The front two throttle barrels had slight gap at the bottom with the throttle closed but the two rear most barrels were completely shut. I checked them with an old carb flow meter and the fronts were flowing 5Kg at idle but the others were flowing 3Kg. With some help I reset the balance via the grub screw and locknut on the shaft between the two ITB's which was incredibly fiddly but eventually we got them all flowing the same. Car now starts and idles way better than before. Thanks mate. Hope this helps anyone else with similar problems