I have recently bought a poorly Tdv8 which cranks for about 10-15 seconds before starting, the starter spins the engine over quickly so the battery is good although I suspect the alternator maybe suspect due to an "f field" fault code.
When it starts I get messages for engine system fault, hdc and special programs off etc, I removed the fuel tank as it had been filled with red diesel so I wanted to clean it out anyway, I replaced the pump in the tank and cleaned the sock as it was well clogged up I also replaced the fuel filter and purged the fuel all the way to the hp pump, now I have nice clean white fuel getting up to the engine I have checked the pressure at the schrader valve and I'm only getting 5psi which seems awfully low but I can't find any data for the low pressure feed but I would expect it to be 45-60 psi? I have also checked dtc's and have faults for fuel pressure being to high and to low but I want to be sure the low side is good before I move on so any help would be greatfully received

Last edited by Sharpy1980 on Sat Apr 15 2017 7:42pm. Edited 1 time in total

Hi does anyone know where I can find the correct fuel pressure specs for the tdv8, I have searched and searched but cannot find anything for this engine, I was thinking of registering for topix but was wondering if there was anything else available like the old rave software which doesn't seem to cover this engine?
For anyone that's interested I'm getting .3 bar at the bleed valve when the ignition is switched on but that drops off when cranking, on the rail I'm getting 220-230 bar at idle and 350 bar at 1500rpm.
I have cleaned the tank replaced the pump in the tank cleaned the sock and replaced the fuel filter but I'm still not happy with the low pressure from the tank, has anyone had any issues with the small regulator in the tank?
Cheers
Lee

LP = 0.5 bar
HP = 1700 bar

The in tank pump is exactly the same as the TDV6, which should give 0.6-0.7bar of pressure, with the ignition on only

One other thing to check is the injector leak-off rate. I believe that if they are worn they allow too much fuel out of the leak return pipe. This (i think) causes the fuel to empty from the injector piping, so you have to crank it a bit, before there is actually fuel at the injectors, allowing it to start.

Obviously you can tell I'm no expert here , and maybe a more knowledgeable forum member will be along soon, or a bit of internet rummaging might reveal a bit more.

Thank you all for your replies, one thing than seems to be certain is the lp is too low as the best has been .3 bar so i reckon I need to address that first so it looks like I need to drop the tank again and replace the pump as a complete assy, they do say if you it right you do it once
@ Erickwan are those pressures you stated that max poss pressures for each system?
@ Disco_Mikey on the tdv6 would it be normal for the pressure to drop off on the lp side around 10 seconds after turning the ignition on even if you release the pressure on the schrader valve?
@CornishRob expert or not I think you may we'll be onto something with the injectors as it does seem to start really well if it has been standing for more than a few hours which if the injectors were sticking open and then slowly closing it would certainly explain that although I'm gonna try and make the lp side right first and the main reason for that is I'm not looking forward to the leak off test as it looks like it will be a pig so I don't want to do it twice lol.
Thanks once again for all you replies
Lee

No tolerance numbers were quoted.

Thanks that's the first printed specs I've seen for the Tdv8 despite searching high and low, my new theory based on that info is the regulator is blocked with the same crud that was blocking the sock on the pump so not only am I not getting .5 bar I think the flow is much below 70l an hour which is why the pressure drops as soon as the engine turns over

If the lip is low, you say in your first post that you've already change the pump in the tank, what with, a 2/h part ? But the pressure is still low ? Did you use a gen filter not a cheap one just asking as was cort out with a TDCI's defender. Owner had fitted a new filter but still had the same symptoms, anyhow to cut a long storey turned out the filter was faulty fitted gen car went like a good un.
Other things to check would be kinked pipes, faulty filter head, correctly fitted pipes after the tank removal.. 2008 G4 RRSport TDV8 current
2009 TDCi 90 current
2018 Discovery 5 HSE lux current
1994 Dakar current

Sharpy1980 wrote:

Thanks that's the first printed specs I've seen for the Tdv8 despite searching high and low, my new theory based on that info is the regulator is blocked with the same crud that was blocking the sock on the pump so not only am I not getting .5 bar I think the flow is much below 70l an hour which is why the pressure drops as soon as the engine turns over

Hi I thanks for the replies,
@Camelrock it was a new pump but only the pump not the complete module so I think the regulator maybe causing the problem but I have a new complete module being delivered tomorrow, it wasn't a gem filter but a mahle which are usually spot on but I will keep it in mind if the lp is still not right after the new pump module👍
@erickwan the only problem with my .3 bar is it drops to zero as soon as I start cranking so I suspect the regulator is blocked or faulty which is reducing the flow to maintain the.3 bar, I am also worried about the house side which is why I only replaced the pump part of the module first but tbh I'm happy I have got the new module coming as I'd happily chuck a hp pump & 8 injectors at it to make it right if need be but I'd hate to change them if it don't need em. luckily labour is free when I can spare the time, tfrom memory the codes were p0191 with p0088 & p0087 and I'm hoping the reason I'm getting high and low rail pressure codes is because the pcv is trying to compensate for the lack of supply??
Cheers
Lee

Yes that's great cheers, especially the p0191 bit which returns after each start up the other 2 only come back when trying to use the car but I am hoping they are being caused by the fluctuation in the lp, the new module arrived today but sadly I was too busy to fit it and it looks like it'll be crazy tomorrow too 😪

Do not discount the fact that all you might need is to bleed out the fuel system.

I used a clear hose attached to the schrader valve and purged the system till there were no more bubbles before starting it so hopefully that should do the trick?
I finally got round to fitting the new tank pump module today which was fairly straight forward except for finding a spare pipe in the tank that I didn't notice last time lol.
After fitting the pump and purging the air from the system I had a steady 5.5 psi with ignition on then 5 psi when cranking and 4 psi at idle so I'm fairly happy with the lp side now although 7 psi would have been nicer, the only trouble is it didn't cure the long cranking or the p0191 code.
Now the lp is good I'm moving on to the hp and hope to check the injectors first the question is how can I do a leak of check on this system with stripping to much off the engine so I can still start it?
Cheers in advance