Voltage drop

[montypsx]

Hi all. how can I check what power my starter is pulling when cranking. If it’s cold I’m not getting 12v to the coil if it’s warm then it starts ok with only a very slight drop to the coil. It seems to only have happened since I’ve done a few mods to the engine e.g 1641 jugs, full flow, 110 cam, twin 34 carbs, ported heads. Any advice would be brill. Thank you

 

[67panel]

The volts will drop to 10 on cold crank giving you a week spark, best thing is to fit a ballasted coil. using a relay fed by the starter crank feed you will get a good voltage at the coil. It will be a 10v coil with the voltage dropped by the ballast , when ballast is bypassed you should still get 10v to the coil. I know easy for me to say (and do) but depends what you are like with leccy stuff.

 

[montypsx]

thanks for the reply, I’m ok with electrics I’ll have a google to see how to do it

 

[naskeet]

The volts will drop to 10 on cold crank giving you a week spark, best thing is to fit a ballasted coil. using a relay fed by the starter crank feed you will get a good voltage at the coil. It will be a 10v coil with the voltage dropped by the ballast , when ballast is bypassed you should still get 10v to the coil. I know easy for me to say (and do) but depends what you are like with leccy stuff.

In cold weather, it's advisable to depress the clutch-pedal whilst operating the starter-motor. This reduces the load on the starter-motor. Likewise using something like 75W/90 transmission oil in the transaxle, also contributes to reducing the load.

Some ballasted coils are rated at circa 6V or 9V, which is why they need to be matched to the appropriate ballast resistance.

https://www.thesamba.com/vw/archives/lit/sparkrite.php

https://www.thesamba.com/vw/archives/lit/microdynamics.php

 

[67panel]

I swear by the Bosch red, ran one on my 5.5L v8 drag car with MSD and same one the beetle drag car . Beetle was a pia to start from cold and kept fouling plugs till I changed coil.