i had a mitsubishi pajero io, smaller brother of pajro. it had almost similar issue. but it would start but didn't rev up. the problem was in electronic accelerator pedal. after waiting for a fem minutes or just jigling that throttle pedal i herd that ticking sound from the glove box area (where were relays positioned) and after that it would start and rev up. well besides all that wiring problem, it might be also key problem...

 

Do you only have one key? This is a bad in itself ... but that is another issue. Does it happen with both keys if you do have both?

The reason people are speaking of beepers or buzzers .. is ... when you get a strange problem like this you have more that one system to check at the same time.

While this is a pain ... you need to make up a test lead with a small 12v bulb connected to the relay control. When you go to start the car this will light when the signal is sent to the relay -- if it does not light --- then you know that the low current control is the problem.

You can also do the same with the high current side - but you will need to disconnect it after the test as the power is always going to this circuit and you don't want the light "on" all the time ... Obviously if the light is out at any time it is connected you have a problem with the high amp feed to the starter. Unfortunately , you could have a problem with this side and still have the bulb light as the current to light the bulb is much less than the what is required to turn the starter. Also -- the new starter could be a problem -- I have had this happen.

You have spoken of testing and checking the grounds -- what people have spoken of is the positive feed coming from the battery that goes through the intermediate bulkhead in the engine compartment on the right side of the car .... this is a known problem area and can cause just the problem you are having .... many ....not familiar with the x308 do not even know about it as it is covered by a rubber boot and just looks like a pass through grommet. Check this area again .. make sure it is clean ... and tight.

 

the bmc is above the pass feet,behind glove box

 

As steveinfrance says "no power to the starter." My problem was the loose nut under the cover on the passenger side where the feed line comes from the battery thru the firewall and is attached to that threaded rod terminal that goes thru to the other "out side" threaded terminal post down to the starter… Removed the rubber boots, tighten nuts on both sides. Haven't had a problem for two weeks.