I have a 2008 Range Rover Sport 51000 miles and the engine failed shells turned on the crank . Had a new engine fitted but the garage cannot get it to run for more than 4 minuits. The fuel pressure drops in the fuel rail . Has anyone any ideas please at my witts end .

they havnt kinked a fuel line when refitting engine have they,i take it you have fitted new fuel filter,when it is running does it rev up properly silverRRS 2.7 TDV6 22"WHEELS FULL COLOUR CODE,STEPS,REMAP..gone
Rimini red rrs 2.7 tdv6 steps. Full c code. Recon engine!!loved but!gone ,thank god !!
Gone rr sport supercharged. Loved but 11mpg !!!
current,triumph stag mk2...current bmw 325 sport convertible

What engine are we talking about? V6, V8. Petrol or diesel? 2x TDV6. SE and HSE. Both returned to sender with issues👀
TDV8 Sport HSE...... Gone. Loved it but it didn't love me!!
Now rolling in MY10 Fullfat TDV8 Vogue. Slammed it to go round corners🙈
Cruising daily #56 mph in a Volvo V8. 😱
Lots of other toys in the cupboard...😜

The OP has a 2008 2.7 TDV6. 2014 L405 SDV8 RR Autobiography

2012 RRS SDV6 HSE -Orkney Grey with A/B bodykit - Now Gone
2007 RRS TDV6 HSE - Zermatt Silver - Gone

Sounds like a coding issue.......and a job done by those that don't know what they were doing  2x TDV6. SE and HSE. Both returned to sender with issues👀
TDV8 Sport HSE...... Gone. Loved it but it didn't love me!!
Now rolling in MY10 Fullfat TDV8 Vogue. Slammed it to go round corners🙈
Cruising daily #56 mph in a Volvo V8. 😱
Lots of other toys in the cupboard...😜

If it was coding, I would expect the car not to start at all.

Any there is nothing that should need coded after replacing an engine. Have done plenty of them, and never even had to do as much as clear fault codes to get them up and running.

It sounds as though it is running out of fuel. Maybe the pickup filter in the tank is blocked, or even a slight leak in the HP side of the fuel system, causing it to loose pressure, and stop running.

A bit more info on how it runs, and how they get it to run again would be nice to help further diagnose

Your presuming that everything was fitted as removed from old engine.
We had a Disco brought to us that wouldn't run correctly and after much head scratching, and several calls to a grown up, it transpired that injectors had been mixed up and were re-programmed which solved the problem. 2x TDV6. SE and HSE. Both returned to sender with issues👀
TDV8 Sport HSE...... Gone. Loved it but it didn't love me!!
Now rolling in MY10 Fullfat TDV8 Vogue. Slammed it to go round corners🙈
Cruising daily #56 mph in a Volvo V8. 😱
Lots of other toys in the cupboard...😜

I will assume you are refering to a TD5 Disco. These do need the injectors coded, and programmed into the ECU.

However, a TDV6/TDV8 engine does not

I assume that you have fitted a Euro 4 Engine, not a Euro 3. In Spain - 2018 F Pace - Frightened away from the Sports due to crank failures
Gone - A couple of RRS, A couple of Disco's. However thinking of another Sport.

Basic engines between EU3 + EU4 are the same, but most parts bolted onto it are different.

Most important will be the fuel system. The EU3 wiring loom will not reach the necessary parts of the EU4 HPFP + fuel rails, and vice versa, so I think this can be ruled out

hi did you get it running if so what was it as i cant get mine to run  silverRRS 2.7 TDV6 22"WHEELS FULL COLOUR CODE,STEPS,REMAP..gone
Rimini red rrs 2.7 tdv6 steps. Full c code. Recon engine!!loved but!gone ,thank god !!
Gone rr sport supercharged. Loved but 11mpg !!!
current,triumph stag mk2...current bmw 325 sport convertible