I've posted a separate thread in General aswell as I need urgent help. I've changed the fuel pump and fuel filter, started the engine and it's running really badly, no throttle and it's saying "Engine failsafe prog".

Can anyone help me as I'm stuck now.

Could be the pump hasn't primed correctly and still has some air in it - turn the ignition on so the lights are on dash, but don't start - leave for 30 seconds, off, then do again, and then on the third time start it. Current Fleet:-
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Tried that earlier, made no difference. If I put it in Drive, it stops hunting and revs at about 1000rpm but still has no throttle. I can push it down to the floor and it does nothing. I've even switched it over to run on LPG and it's exactly the same !

Tried disconnecting the MAF and then starting. Would you believe it starts and runs perfectly, normal throttle response and no engine failsafe warning. Does this mean the MAF is knackered then??

So after all my issues, replaced the fuel pump and filter. Cleaner the Maf and inlet etc which resulted in it running fine last night. Started it this morning and I have the same problem still, took about 10 seconds of cranking before it coughed and spluttered before firing up !!

Not a good start after it appeared that you had cured it!. Have you checked the Schrader value to ensure that you still have pressure & that the return valve isn't playing up.
Possible next step is a new return valve & sensor, that way you can pretty well eliminate the fuel side of things.

Keep at it you must be close.

So I've now replaced the fuel pump, fuel filter and a new Bosch Maf sensor and I still have the original problem with it struggling to start from cold. If it's only left 3 or 4 hours for example it starts up fine but when left all day or overnight it cranks over for a lot longer and when it fires up it's not on all cylinders for a second or two.

it sounds like the pressure or fuel is bleeding back out of the rail over night.

there is a filter/ pressure regulator located on the outside of the tank on the passenger side, looks like an in line fuel pump.

have you checked this is not leaking/working OK. There is nothing that can't be fixed with a hammer😜😜
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Yep, replaced the fuel filter at the same time as the new fuel pump.

Unfortunately I'm still suffering with this issue of it not starting properly. What I've noticed after it being parked up for 4 days is that it fires up straight away exactly as it should. I'm thinking that something is leaking into the cylinders overnight causing the starting issue in the mornings, when it's left for a few days whatever is in the cylinders has cleared, either Petrol, lpg or coolant. I have been losing some coolant over the last few weeks which I've found was some hoses at the back of the engine. I haven't used it enough since to monitor any coolant loss.

What can I do from here to try and pinpoint what's causing this frustrating issue ?

Had similar problems, pulled the Maf and Plenham intake off (also splutters if the intake is on loose) and cleaned the butterfly, front and back - you can twist it and get it with a wet wipe (they were handy got me a one yr old lad!) - DON'T drop anything in!!

Nice free check- it was black before cleaning.