schematics and diagrams: Intermittent starting issues on Volvo 760?

In this case the volvo was sitting for few years.After that the customer replaced the battery.But now the volvo will not turn over first,then suddenly start after few hours.
It does not want to turn over and will not start but either later that day or maybe the next morning it will start....sporatically, not always.

It sounds as if your starter motor is failing. Just to double check that, Pull the gear stick out of park and try starting vehicle in Neutral. if it will start in neutral everytime then it is most likely the park/neutral safety switch. If placing it in neutral makes no difference, then grab yourself a 12 volt test light. Pull the small wire off the starter solenoid and see if you have power at the starter solenoid when trying to crank the vehicle. This will be easier if you can get another person in the car while you check for power on the small starter solenoid wire. if you don't have power to the starter solenoid when cranking then I'd say the ignition switch was bad, However, thats not the most likely culprit. If you do have power to the solenoid wire when cranking but the vehicle doesn't crank then I'd replace the starter motor.

BUT IF IT CRANKS EVERYTIME AND NOT TURNS OVER EVEYTIME.
IN THAT CASE THE PROBLEM IS DIFFERENT>

If it does "crank" It just won't start then? A cranking issue is when the engine won't spin. A starting issue is when engine will spin when hitting the key but won't start. Is the check engine light on by chance? Very well could be the fuel pump relay. Or suppresion relay. Over by the over flow tank on the passenger inner fender well. See if you have 2 black relays clipped to the overflow tank. If you do, try swapping them from connector to connector. One is for cooling fan, other for fuel injectors. see if it fires up then.

Also go through this additional details too ...........

That cause a no start condition on your vehicle are the fuel pump relay and the crank sensor.

LOCATION:-- The crank sensor bolts to the back of the engine near the transmission bellhousing and the harnesses are bad to get frayed.

LOCATION:-- Also the fuel pump relay behind the ashtray on the relay block are known problems.

You can inspect the crank sensor wiring harness with a flashlight and if its frayed at all replace it. If it has a yellow stripe around the harness near the connector its original and I'd replace it.

The fuel pump relay is behind the ashtray on the relay block back towards the left and they are known problems. It will have a date code on it. If its original I'd try another one. You can pull the dual relay out of its protective cover and look at the solder joints on the printed circuit board. If you see a solder joint cracked you might get lucky and resolder it. Or if your not handy with a soldering Iron I'd just replace it.

This details will help.
Thanks.

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