T595 Not Starting

Cheers guys. So yes have cleaned the starter switch properly and it does give a better contact but not cured the fault.
Battery drops to 12.6v and holds and yes fully charged from new.
I'm hoping taking the starter out is a last resort mainly as i' m trying to find why the start button won't activate the solenoid. When the bike was running it always turned over kind of slowly anyway. I presumed all T595s did.
After studying the wiring diagram I'm thinking the main power relay could be at fault giving the low circuit voltage. Turns out I replaced the light inhibiting relay before.
This is Hella 4RA 940 010-71but guess what? Can't get them new so now I'm stumped yet again. Should I go for a used one?
Sorry if I don't always give specific results guys. I get little time at it and am so far out of my comfort zone and have no internet at the mo as have moved house too.

 

Not sure how to take that Sprinter

Right now I would bite your hand off if you offered me a grand for it.
I found a replacement relay that isn't Hella but has the same contact layout and rating so should have it in a few days. I'll be cleaning all plugs and earth points before I fit it. The problem with that is I would never know the real culprit if the issue disappears.
As always many thanks for all input

 

True.
Just been back out to Check the voltage at the power relay socket.
Ignition off = 13.4v at battery.
Ignition on = 12.4v across battery and 12.2v at Power relay socket.
So power relay probably not at fault.
Next job full contact clean up. Fingers crossed

 

Ah that's interesting. I may as well try that while it's all apart.
Although thinking about it I do have a loop of thick wire with an inline fuse coming out of the loom. I thought this was because the holder in the fuse box was u/s but it could be that mod. I'll try to post a pic today. Cheers Biglad

 

I have a feeling its 12.2v but I'll double check. As stated it's a brand new sealed battery with around 100 miles on it and it's been on trickle charge when not in use so I'll be well pissed off if it's fooked.
I will test with a car battery and post the results asap. Thanks again...

 

Hi guys here's the latest.
I connected a leisure battery with 13.4v via jump leads. With ignition on it dropped to 12.4v in a few seconds. With the jump leads disconnected and ignition off the bike battery gradually rose to 13v. So the battery is healthy.
I then connected jump leads from my running car and 14.4v to bike battery. With ignition on it showed 13.4v at battery and 12.4v at start button.
Then connected direct to the bike leads (not connected to bike battery) showed 14.4v to earth lead at the frame. 13.4v at Power relay and 12.4v at start button.
There is only 0.2v at the fuel pump connector. So now thinking the fuel pump relay maybe faulty or does it only go live with the engine turning over? One side of the start button is connected to the coil in the relay which then connects to the ecu..
Head throbbing now.....
.