Member Since: 08 Jun 2022
Location: South
Posts: 16
How best to bleed the air in those pipes? This is getting beyond my knowledge! I bled air from the LPFP side but considering the time we had the system open I would have expected more air to come out… Wiring seems okay from what I can test, fuses intact.
7th Jan 2024 5:20 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4678
A long crank period should do it, (10 to 15 secs) if everything else is OK. To confirm there's fuel at the injectors you could loosen the pipes to each injector and crank until they are wet. A word of caution here though, this is extremely high pressure so stay well away from the engine while it's being cranked. If you get hit by the spray it will hurt you, and can be serious!
Allow 30 secs for the pressure to fall back before investigating for diesel. Make sure the battery is full before you begin. 12.8v.
Check again for codes.yµ (idµ - eAµ) ψ=mψ
7th Jan 2024 5:50 pm
ds23man
Member Since: 19 Jan 2013
Location: Ainum
Posts: 227
Loosen the pipe at one injector at each bank. Crank for ten seconds with nobody in the vicinity of the engine bay. Thighten the pipes and see what happens. Had to do this after my HPFP replacement.Citroen DS23IE
Audi A6 2.4 V6 Avant Quatro (1998)
Audi 80 2.6 v6 Cabriolet (1996)
John Deere 4240S
McCormick 323
7th Jan 2024 6:24 pm
StillBasilisk
Member Since: 08 Jun 2022
Location: South
Posts: 16
Hi both, so I have been away from the car since the weekend so not had a chance to crack the injectors yet, my father in law is there and has been doing various things - he got it to start with some easy start at the intake, it would idle but wouldn’t rev on throttle. I’m intending on bleeding the injectors when I’m there but does this sound like it’s air in the system? My pessimism leans towards the pump or something we have broken but I hope it is just air… thanks for your help; as ever, appreciated.
9th Jan 2024 7:10 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4678
Not an air issue if it's running, but there should be codes there now. Not revving could be a duff hpfp or an EGR issue.
Check the codes.yµ (idµ - eAµ) ψ=mψ
9th Jan 2024 7:15 pm
StillBasilisk
Member Since: 08 Jun 2022
Location: South
Posts: 16
I have the reader here so he can’t check the codes. Didn’t think to take it out my bag! Thinking about it, when I tried cranking earlier I took this photo. This implies there is no pressure in the rail to me? Which implies a leak, surely if it was an enclosed circuit it would build pressure even slowly? Sorry for the roundabouts, and I know I just need to read the codes when I’m down there, it’s just driving me crazy why I can’t figure it out!
9th Jan 2024 11:13 pm
StillBasilisk
Member Since: 08 Jun 2022
Location: South
Posts: 16
I have the reader here so he can’t check the codes. Didn’t think to take it out my bag! Thinking about it, when I tried cranking earlier I took this photo. This implies there is no pressure in the rail to me? Which implies a leak, surely if it was an enclosed circuit it would build pressure even slowly? Sorry for the roundabouts, and I know I just need to read the codes when I’m down there, it’s just driving me crazy why I can’t figure it out!
Click image to enlarge
9th Jan 2024 11:14 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4678
Yeah that pressure is way too low, you need a minimum of 150 Bar (15000 kPa) just to get it to fire! At idle you should expect to see around 275 Bar (27500 kPa)
Looking at the VCV and PCV they seem to be struggling for fuel. (At idle they'd be reading 21.5 and 13.5 respectively!)
If there was a leak you'd surely see it?yµ (idµ - eAµ) ψ=mψ
10th Jan 2024 12:46 am
StillBasilisk
Member Since: 08 Jun 2022
Location: South
Posts: 16
I’d like to think I’d see it, if the valves in the HPP are starving that implies the leak would be before the HPP, or within it? The valve at the back of the engine has a solid flow of fuel (I can check the pressure when I am down there) so I’d suggest the low pressure side is working. So to me that rules out a leak before the pump, assuming pressure is correct. 110kpa isn’t far off atmosphere so the leak must be enough that I’d see it at that point, if it can’t build pressure at all. This whole debarkle is driving me insane, it’s like a break up!
10th Jan 2024 9:53 am
StillBasilisk
Member Since: 08 Jun 2022
Location: South
Posts: 16
So I have ventured down to the car this weekend, to read the codes and to have another crack at diagnosis. Applicable (I think?) codes below:
Click image to enlarge
I had let the battery die down last week whilst cranking so there are some faults relating to that. With that said, I set up for a leak-off test (some of those clips are tough!), cranked the engine: nothing. No fuel whatsoever flowing through the leak off set up. Cranked it a couple of times and no fuel. I took the nut off the fuel rail at first injector on the left bank and cranked the engine, I can only describe it as low pressure, fuel bubbling out of the open rail. Certainly not dangerous high pressure as I understand it is supposed to be.
My thoughts at this stage:
1. If fuel were only to enter the leak off pipe when the engine was running, surely pressure would be building up in the system, unless the injectors are still firing but at a much lower pressure?
2. When I started the car after first changing the HPFP and it ran for the duration it did, I assume the pump was working initially as the car drove and reversed, therefore pressure must have been in the system as I can’t start the car with no pressure.
3. Everything at this stage is persuading me that the HPFP has gone kaput during the initial operation, rather than something as a result of the install.
4. One of the injectors doesn’t seem as dry around the main injector as the others, but this is located under the coolant hose I disconnected during install so I’m leaning towards it being coolant, regardless that is only 1 injector which would still allow pressure on the other rail?
Tomorrow I think I will have to take the HPFP out and send it back under warranty. Thoughts welcome and appreciated as ever!
13th Jan 2024 8:27 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4678
The fault codes are telling you that either you have a fuel leak or the HPFP is malfunctioning. But make sure you diagnose correctly before condemning the HPFP.
The leak off pipes are mainly the return for the unused excess fuel from a running engine. There is no meaningful pressure there as such, as this fuel is returned to the tank. But, if you suspect an injector is leaking this will kill the pressure for all injectors, as both fuel rails are connected at the diverter rail. This will cause the HPFP to struggle in building pressure it obviously can't. So check it's not diesel at that injector instead of coolant. Remember you need a minimum of 150Bar just to fire the injectors, and
the entire fuel rail only holds around 34cc's of fuel, so a tiny leak is a critical one as well as dangerous.
Speaking of which, the danger you refer to is mostly when the engine is running. However, if you already have an injector line open the rail can't build pressure, so there is no danger from pressure in that scenario and fuel is just a dribble. It's when the closed system is or has been operating, and you attempt to open a high pressure line. The risk here is being hit with fuel spray at 27000 bar, and that will do a very serious or even life threatening injury. It is depleted pretty quickly though after the engine has been switched off, and totally safe after 30 secs. As a side note, don't be tempted to unplug an injector while the engine is running, if it remains open it will be walloped by the piston on it's return resulting in damage.
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