I'm having problems with my 10P TD5 and I think it looks like a high fuel pressure issue. It's having trouble starting and when it does it sounds like only one cylinder firing and there's lots of white smoke out of the back. With time and a bit of revving it gradually improves until it's somewhat normal except the throttle response is pretty bad.

A few months ago it needed the fuel tank removing to get some welding done for the MOT. When they put it back together the fuel pump was broken and the garage later told me they'd since learnt that they should have priced in a new pump because they apparently always break when the tank is lowered (they made me pay for a new pump but labour was free (I'm not sure how much truth there was to this claim)).

I started having problems a while after that and I'd put it down to maybe dodgy glow plugs as it was getting colder. Most of them were broken but replacing them didn't change anything. Then I suspected the fuel return hose was blocked (I'd assumed something got dislodged while changing the pump) so I when to remove the valve and the fuel filter assembly dissolved so I had to replace that whole thing. I thought that would be the solution but it's still not any better. I'm not going to take it back to the garage because we didn't part on god terms. I'm thinking now I need to be doing one of the following:
1. Removing the fuel system hose in different places and running the purge cycle to try and isolate the problem.
2. Checking out the fuel pressure regulator (apparently I can't check fuel pressure here, what does the electrical connector do then?).
3. Removing the fuel tank to check out the pump (I have no idea what I'm doing here or how feasible this is).

The pump tends to whine a bit when started up but then tails off to a quieter, more consistent, sound. I was going to check the fuel pressure regulator next but searching for this most people only seem to have problems with it leaking rather than seizing up, which I'd suspected.

Can anyone share any experience?

Okay, I remembered I have an endoscope camera so I’m going to look at the fuel pump. I think looking at other things may just be wishful thinking, I’m probably just going to have to get to the fuel pump.

They can break off the pipes, when they forget to disconnect them, as the tank comes off...

For the sake of £20, you can get a fuel pressure tester delivered in a week. Remove the temp sensor on the FPR, and screw it in. You should get 4 bar, whilst the pump is running. Much cheaper than throwing a parts cannon at it, and you can use it again and again to diagnose fuel issues.

Ebay Fuel Tester

Bumping this because I finally got hold of a fuel pressure tester kit. I plugged it into the sensor and just ran the fuel pump rather than turning the engine on.

Since I thought the fuel pressure regulator was stuck closed I was expecting the fuel pressure gauge to shoot up and go way beyond 4 bar. In fact what happened was the pressure gauge shot up to nearly 4 bar, something like 3.7, then as soon as the fuel pump turned off it dropped right down to 0, like the needle couldn't drop any faster. Does this mean the fuel pressure regulator is actually stuck open? I don't appear to be leaking diesel anywhere.

The other symptom is that the fuel pump makes a rather loud whining sound when it starts up which soon disappears. If the regulator is stuck open then could it mean that all the fuel is draining out of the system and the pump is starting dry?

If I need to replace the regulator does anyone know the part number for that bit inside the regulator part inside the assembly? The bit that looks like this but without the thing sticking out of it:

I do believe the sticky out thing is just a drain if it fails.
I repaired two with a repair kit and both have been successful, no idea if it's your problem, ours were leaking but drove ok.
Fuel pumps do whine in general in my experience.

Mine's okay once it's warmed up and on a motorway but it's not starting well and and it's weak at lower revs and has poor throttle response.

How about injector seals and washer?
Injector loom been replaced recently?
Oil in the red plug on the ecu?
Any codes been read or live data?

The cylinder head was replaced a few years ago and I swapped all the injector seals and o-rings and I replaced the injector harness as well. I checked out the red ECU plug and there's nothing in there and I haven't seen an engine warning light but I've not plugged it in to check for codes. The new regulator just arrived earlier but I don't think I'll have time to replace it until Tuesday, maybe Thursday. We'll see then. I'm hoping I can get to it without having to remove the whole regulator assembly, looks like it's just a circlip holding it in.

Also replace the red rubber duck lip seal, at the fuel filter. Its there to stop the entire fuel pipe draining back into the tank when you turn off. It acts as a one way valve.

DA3950​

I replaced the fuel filter assembly. It’s in there isn’t it?

Yes it is....