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[horsecow]

Bit strange but here goes. Car starts first go every morning and once it has been sitting for a while but once it has been running for a while it doesn't start. Once it has been driven for a while, I can turn it off and then try to start again but it doesn't even try to turn over. Its like the battery is dead but once the I turn the key back I can turn all the electrics, on and leave them going for ages so I presume its not a dead battery I have. The car starts immediately from a jump or even the slightest push when hot. Is it possible I have a bad connection somewhere, the battery terminals all look good and don't seem to be heating up? Could it be a starter fault? I'd like to get this sorted at the weekend so any help on what to look for and where would be much appreciated. Someone also mentioned a bad earth connection could cause this??

I know I need to get some voltage readings so will pick up a multimeter tomorrow or friday. Is there any particular type or model of multimeter I should try to get or are they all the same?

[Kevin Wood]

Are you saying the dash lights come on but the starter doesn't run?

Do the lights go dim at all when you turn it to the start position?
Do you get a click from the stater solenoid?
Does it help if you waggle the gear selector with the key held in the start position or start in "N" instead of "P" position (assuming it's an auto)?

[horsecow]

When car is cold everything works as normal. I've just done a bit of a test this evening. Car hasn't been started since yesterday evening, went out and started fine, drive for about 2 minutes, switched it off and then it started again perfectly. Did this 5 times in a row then went for a half hr drive switched off and no start. The dash lights all come on as normal but when I turn the key on round to start it tries to turn over once and then all the dash lights go out and the radio is now in safe mode. If I use the jump leads or a booster pack the car will start instantly. It seems to be pointing towards a knackered battery but I'm confused as to how it always starts when cold but not once it has been driven for a while.

Oh and its a manual.

[Kevin Wood]

Frequently, an engine turns over more easily when cold due to dry bores meaning the compression isn't as strong. Heat also increases the resistance in the starter motor windings.

My first check would be the security of all connections in the starter circuit. Battery terminals often suffer where the large starter cable is crimped into the terminal. If these work loose there can be high resistance here which eventually causes problems. Often, the battery terminal will get hot when running in this case. Look also at the connections from battery negative to chassis and engine block (under the air con pump, IIRC.)

If nothing's obvious, this guide may help:

http://www.omegaowners.com/forum/index.php?topic=90619.0

[horsecow]

Thanks for coming back to me Kevin. Got fed up with it at the weekend and went for a new battery. Whilst swapping them over noticed that the earth connection (engine block to sub frame) had frayed almost completely through so replaced that as well. All connections around the battery look and feel to be in perfect condition although I didn't get time to check connections round the starter. Hasn't missed a beat since the new battery went in so hopefully that's cured it. Fingers crossed, I'll be back if it starts again.

[Keith ABS]

  it would have been the frayed earth strap causing it
keith B

[albitz]

Definitely. I had exactly the same with my Cavalier about 6 mnths ago.

[horsecow]

Hmmmm possibly. I had a bit of a wait on the new earth strap coming from town so I fitted the new battery and was talking to a mate who said that the earth strap was pretty pointless anyway so I decided to see if it would start without it and it did!?!?!? Started every time without fail so I'm not totally sold but either way I've got a new battery and earth strap and its working fine since  . (Didn't like to leave the earth strap off as it was only £3 and it obviously serves some purpose)

[Andy H]

Something has to carry 150 amps from the starter to the battery when the engine is cranking.

If the earth strap is frayed or missing then other cables that are not suitable may take the load instead (throttle cable, earth lead to ECU perhaps)

It isn't as big a problem as it used to be because many things are now rubber mounted (throttle cable for example). In the good old days the throttle cable could get red hot and boil the petrol in the carburettor