Poor starting from cold

[whitesnake]

Hi all,
I am experiencing difficult cold starting at the moment and would consider all advice, my car 1970 4.2 ots triple carbs, petronix ignition , high torque starter, ballast resistor. From cold with full choke it will catch if I do short bursts on the starter, it seems to get higher current as I switch off starter and it will fire, I have fitted test lights to the plugs and this shows on cranking a poor light then as I stop starter and engine fires it has a brilliant spark. I was just thinking is this to do with the ballast resistor not being compatable with my setup. Car was originally LHD with Strombergs and ignition setup is as original with ballast resistor. If I just keep cranking on full choke it will not fire and flood hence my short bursts on starter.
Any thoughts ?
Steve.

[christopher storey]

The phenomenon you describe is known as " coil robbing" . There are several possible causes . The first aspect I would check is battery voltage during cranking. If this drops below perhaps 11.8 volts ( others may suggest different figures) then it suggests that the battery has insufficient cranking capacity - usually something in excess of 600 amps CCA is suggested for the XK engine - and you might try assisting it with a jump start from a running engine . If that is not the problem the next thing I would do is to substitute for your present coil a known good coil of a suitable type for your pertronix set up and see if that improves the visible spark quality/duration

These engines are not great starters from cold unless they are used daily. One of the reasons for this is that the inlet tract is so long that to " refill" it with mixture after a period of disuse takes quite a lot of cranking- certainly on all my XK engined cars I would say that I need at least 5 15 seconds bursts on the starter even to get a kick out of it - so perseverance is a virtue !

PS a failed ballast resistor will also produce the effect which you are experiencing

[whitesnake]

Christopher,
Thanks for reply, I did wonder if the coil is correct, it is the one supplied with car from US so could be suspect, also could replace resistor to try that. Battery is fairly new and for e type so think that is not an issue.
If you crank in short bursts the same as I am doing it sounds as though it is a peculiarity of the XK engine.
Regards Steve.

[christopher storey]

Steve : another thought. I have found when confronted by this problem that cooking the plugs in an oven at say 100C for 1 hour can make a surprising difference ( and yes we are still married after 53 years ! )

[whitesnake]

Christopher,
Yes , interesting thought, I actually used to do that ( well warmed plugs on an hotplate ) on an old ford van we had on the farm because it had low compression and was a pig to start in the cold. On my present problem I have been reading up about the pertronix distributor and they recommend fitting a 3.0 0hm coil and removing the ballast resistor so I shall try this. It will be the last adjustment I should need to do to remove the remnants of US spec that my car suffered.
Regards Steve.

[mgcjag]

Hi Steve....i would also check that you choke mechanism is adjusted correctly....Steve

[whitesnake]

Thanks Steve,
Yes that was my first port of call but all is working fine with regards to choke and cables.
Steve.

[gtjoey]

Steve, if you have pertronix, BYPASS THE BALLAST.......YOU WILL DESTROY THE PERTRONIX.
Your not getting full 12 volts.
Good luck
Just jump the wire......

[whitesnake]

gtjoey,
Hi just an update on this post, I have now fitted petronix 3ohm coil and removed the ballast resistor and she starts like a dream, full choke one small blip on starter and she fired straight up, brilliant.
Instructions for pertronix state remove ballast resistor on this system, but previous owner had left it in the system, so now all good, really chuffed, best starting ever.
Steve

[mgcjag]

Hi Steve...great that your now working ok......however for anyone else searching a Pertronix can be used on Ballast systems...you need to wire it as per the instructions....Steve

[whitesnake]

Steve, This is so confusing as my pertronix instructions for a D177600 distributor states compatable coils are3.0 ohm and adds note: Remove or bypass external ballast resistor or resistance wire when installing the recommended flamethrower or HV E-Core coil.
I do note the instructions you show are for a 1.5 ohm coil so all I can go by is my set of instructions and the way the car is starting with my setup which so far is absolutely brilliant, starting from cold on the button every time. The moral here is I think , check which coil you are using.
Best regards Steve

[mgcjag]

Hi Steve...i see the problem....there are different "Pertronix".....the complete distributor unit......and the points replacement unit that fits in a standard distributor(Ignitor)......so different instructions depending what "Pertronix" your useing......Steve

[gtjoey]

This is why the Forum is so great!
The owners as well.....
With the 4 billion ive done or helped, overall for a replacement unit .
Using a 3.0 coil, no ballast in a series 2 and non copper spark plug wires.
Along with ngk plugs pre gapped 30-32ish.
Im in the camp that the 1-2-3 set up blows away the pertronix but if your comfortable with it.
The above set up is the most reliable and compatible
HAPPY YOUR CAR IS RUNNING SO SWEET, PLEASE RETIME THE ENGINE AND GET THE PLUGS, IT WILL TRANSFORM THE CAR!
GOOD LUCK
GTJOEY1314
P.S. THOSE directions are a little old,they have proven you need a FULL 12VOLTS or the unit strains and burns out.
The 3.0 gives enough resistance without burning the unit out with too much with the 1.5
3.0 overall is the best choice.