Groundhogs 1, 2, 3, 4

[Mr Cerbera]

Hi Team,

Sorry to be The Numpty again

BUT

Have been running BlackBeauty© quite a while now, alternating between two batteries when necessary.
It dawned on me lately that, although they each have a charge of 12+ volts, they both have problems turning the motor over when it is cold.

Do you think that I have a dodgy earth or can you suggest another problem that I may be suffering ?

Many thanks,

PJ

[Byker28i]

The earth cable to the engine is easy to see. It goes from battery negative to the chassis and then from that point onto the engine.
When mine was frayed it caused all sorts of weird electrical issues as it was making and breaking as the engine moved, which was really annoying as it was returned to me like that after the new engine went in - for the sake of £30 of new earth cables...

[TwinKam]

An easy way to check the efficacy of your earth cables is to temporarily connect a GOOD QUALITY, HEAVY DUTY COPPER jumpstart lead direct from the battery negative to the engine block (or, better still, the body of starter motor). If that instantly improves the cranking speed, you've proved something....

[Mr Cerbera]

Cheers Guys,

Most appreciated

(Now I'll just have to nip over to our local Church's Roof!)

[Penelope Stopit]

Remove fuel pump fuse or relay

Connect voltmeter between battery negative and engine block

Crank engine over

Voltage on meter should be no more than 0.25 of a volt

Quarter of a volt volt drop is the max acceptable for the earth side

---

Remove fuel pump fuse or relay

Connect voltmeter between battery positive and starter positive

Crank engine over

Voltage on meter should be no more than 0.75 of a volt

Three quarters of a volt volt drop is the max acceptable for the live side

---

Battery voltage should not drop below 9.6 volts when cranking

[gruffalo]

Mr Cerbera said:

Hi Team,

Sorry to be The Numpty again

BUT

Have been running BlackBeauty© quite a while now, alternating between two batteries when necessary.
It dawned on me lately that, although they each have a charge of 12+ volts, they both have problems turning the motor over when it is cold.

Do you think that I have a dodgy earth or can you suggest another problem that I may be suffering ?

Many thanks,

PJ

If you have been using these batteries for a while they could well show 12volts but are no longer able to deliver the required current, the tests suggested by Penelope will show this up, if the Battery voltage drops below 10volts when cranking then I suggest you need to invest in a new Battery.