Intermittent power loss (battery) on starting

[kernelFergus]

Hi,

A couple of days ago, we started to have a very intermittent fault, wherein upon starting the engine, there is a click, then nothing. All power is lost and turning back the key does nothing.

 

The first time, I rolled the car back out of the garage and did a very small push start (barely enough to turn it over once) and everything suddenly came back to life.

The second time, simply closing the passenger door brought back the power and the car started as normal. Aside from this, it drives perfectly and has started fine at least 20 times between these incidents.

 

Any advice would be greatly appreciated.

[m1tch]

When there is an issue do you see a red light flashing quickly on the dash? It might be that the immobiliser is coming on if the fob battery is going/the pick up ring around the key is going.

Have you checked that the battery is tightly connected?

[Tdci-Peter]

On 17/08/2016 at 2:26 PM, kernelFergus said:

there is a click, then nothing. All power is lost

I would check the main power leads (the fat ones) from the battery to the starter. Including the earth connections, one from battery to body, and one to the engine, usually near the starter motor. Check tightness of the bolts, and feel the wire near the crimp terminals. It can break inside the insulation, it will feel floppy or bendy compared to a good one. Including the battery connections, of course.

Sounds like any vibration (door, car movement) gets the connection working again. If it only happens after the click, then the fat leads are the prime suspect, as they carry the starter motor current.

[kernelFergus]

Despite being subscribed by email, I didn't get a notification that somebody replied :/

Regardless, I tightened the main battery leads (didn't seem that loose to me) and it's not done it since, so it looks like problem solved.

[Tdci-Peter]

6 hours ago, kernelFergus said:

I tightened the main battery leads (didn't seem that loose to me)

Corrosion can build up inside the connectors, and they can seem tight, but there is an insulating layer. It does not need much, the contact resistance has to be very low.

If it happens again, remove the terminals, clean gently but thoroughly with fine sandpaper (both parts), smear liberally with petroleum jelly (Vaseline), and re-fit. Be careful not to over tighten, it could damage the terminal or battery.

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