Voltage drop and slow cranking

[cheshired5]

Originally Posted by pphilpot

Yup, I have the undertray, and I removed and refitted the positive cables to the starter a month or so ago when I cleaned the turbo control valve.

The very first crank sounds slightly laboured but not in a way that would concern me at all and then I think it turns quite nicely.
If you're getting that, low sub 0.5 voltage on your earth cable during starting, I wouldn't worry.

[KBB]

A battery pulling down to 10.8 is ok but the may be voltage drop on either the supply cable to the starter or the engine to chassis ground. Where the battery is in the boot I would test as follows:

For supply side first connect meter across battery pos and negative crank and note the pull down voltage as you did above. Move to the starter motor and place red probe on the starter terminal stud (not the cable eyelet) black probe on the engine to chassis ground terminal at the chassis, crank the engine and note the pull down voltage. Subtract this voltage from the one obtained at the battery the difference between the two is the voltage drop on the supply side and should be below .25v

Ground side test place red probe on engine block, black probe on the the engine to chassis ground cable eyelet crank again and note the voltage on the meter. No move to the battery connect red to the battery ground cable termination point on the chassis and the black to the battery negative terminal (centre of the negative terminal and not the actual connector) crank again and note the voltage. Add the two voltage obtained on the negative side and they should be below .25v giving a total starter circuit permissible voltage drop of 0.5 v or less.
HTH

[pphilpot]

Thanks KBB, I'll try that tomorrow.