Member Since: 12 May 2021
Location: Durham
Posts: 18
Fuel pressure issues
Hi all, first post and should say amazing forum that has already helped me with my central locking and sunroof drains and lots of other bits. Great members and support on here.
I have an issue and I have read lots of posts with similar issues but looking for support as I can’t seem to sort this!
Had low fuel pressure issues with the car occasionally dropping to limp mode with engine fault messages. Following advice from others on the forum I have an obd11 that I bought which is great and showed up the injector pressure low, fuel pressure low errors one ending 22090 from memory.
I had 4.5 psi pressure at the schrader and not much fuel flow so dropped the tank and put a replacement low pressure pump in the tank (complete new unit with sender etc). Great news it sorted the problem (only had 5psi at the schrader valve) but car ran perfectly, (sorry new fuel filter aswell)I went out for a day off roading in it and was running great all day up until I got stuck in a boggy piece of land (full permission to use land etc). The car then idled for a while as was trying to winch out but cut out. Got winched out, there was air at the schrader valve but bled through and back up and running.. but then has started to drop into limp constantly and can’t get the car above 10mph without it cutting out and dropping into limp mode.
So dropped the tank again, all appeared fine, replaced the pump element of the in tank system again in case a faulty unit.. car ran fine on startup and appeared improved. But dropping into limp mode again. 5psi at the schrader and no air just looses power. Another brand new genuine filter on, still exactly the same and same errors coming up.
My thoughts are I’ve done something wrong but it’s all pretty straightforward so don’t think I have, or it’s a different fault.
Using the obd tool shows the car fuel pressure builds as you accelerate and then starts dropping hence then going into limp mode.. car starts fine. Really confused with this as it was running great a few days prior.. any help really appreciated.
Also if I put a gauge on the schrader valve when I Rev the car the pressure drops to 0 at high revs and wondering if this indicates a problem on the low pressure side but it’s had 2 new pumps and not even done 3 miles on the new one!
Hoping someone can help, my thoughts are is the high pressure pump playing up and needs replacing or is it an issue with something on the low pressure side as reading on here I should be getting 7psi and I’m not even on 2 new pumps..
12th May 2021 1:27 pm
aja4x4
Member Since: 14 Apr 2019
Location: Westbury
Posts: 2463
Are you replacing the whole pump unit with a genuine one or just replacing the fuel pump itselfAndrew
D3 2.7tdv6 2005
D4 3.0 SDV6 Commercial died and gone to LR heaven
D5 3.0 SDV6 HSE
12th May 2021 2:51 pm
Rossi84
Member Since: 12 May 2021
Location: Durham
Posts: 18
Hi, I replaced the whole unit first time which resolved the issues for most of a day but then the issue got much worse.
Second time I have used the original housing where it was still working fine for most of
The time but with a new walbro pump in it.
Thanks
12th May 2021 3:25 pm
aja4x4
Member Since: 14 Apr 2019
Location: Westbury
Posts: 2463
If you replaced the whole unit with a geniune one it has a 2 year garantee, the seperate pumps only last a few months.
If you fitted a genuine one and the problem got worse its got to be something else thats causing your issue, dod you use a genuine filter?Andrew
D3 2.7tdv6 2005
D4 3.0 SDV6 Commercial died and gone to LR heaven
D5 3.0 SDV6 HSE
12th May 2021 5:38 pm
Rossi84
Member Since: 12 May 2021
Location: Durham
Posts: 18
Hi Andrew, I didn’t use a genuine filter and have just replaced it with a Bosch filter. I am thinking my issue is something else but not certain especially when I read on here that there should be 7psi of pressure at the valve but I haven’t ever got that. Seem to get 5 max
12th May 2021 8:31 pm
aja4x4
Member Since: 14 Apr 2019
Location: Westbury
Posts: 2463
You may need to check the voltage at the pump you could have a corroded connector or a faulty relay.
The other reason i ask about you fitting a genuine pump unit is it has a pressure regulator built in, if your just replacing the pump it could be the regulator at faultAndrew
D3 2.7tdv6 2005
D4 3.0 SDV6 Commercial died and gone to LR heaven
D5 3.0 SDV6 HSE
12th May 2021 9:07 pm
BradC
Member Since: 29 Apr 2019
Location: Perth
Posts: 119
Do you gave a GAP IID or similar? Log the volume control valve, pressure control valve and fuel rail pressure.
It's sounding like an issue with the high pressure pump.
13th May 2021 5:57 am
Rossi84
Member Since: 12 May 2021
Location: Durham
Posts: 18
I’ll do this tonight as I have got a gap tool. I’ll get some measurements and post them. When I drive it with it in live view on pressure it starts building with revs then suddenly dips which is when it goes into limp mode. On another run it started building but while still accelerating starts dropping while throttle still down then again goes into limp mode. I’ll post up later after checking the values you have said. Thanks and really appreciate all the help
Last night I was checking the current drawn across the fuse for the in tank pump and was holding around 9 amps, did spike on start and lowest was 8 amps. Fuel pressure at the schrader never got above 5.5 psi though. I did think I heard the pump sound to spin faster and saw a slight spike in pressure this was all while bridging the relay.
Thanks again for all the help and hopefully will get this sorted
13th May 2021 12:55 pm
Rossi84
Member Since: 12 May 2021
Location: Durham
Posts: 18
Hi really appreciate the help, I’ve added the photos from the gap tool of
The sensors although one doesn’t have a reading. There as below but not sure what this shows or if normal or not! Was raving up ok while this was being done.
16th May 2021 2:13 pm
aja4x4
Member Since: 14 Apr 2019
Location: Westbury
Posts: 2463
Dont worry there is no reading from the pressure sensor you will find it under somthing like rail pressureAndrew
D3 2.7tdv6 2005
D4 3.0 SDV6 Commercial died and gone to LR heaven
D5 3.0 SDV6 HSE
16th May 2021 2:22 pm
Rossi84
Member Since: 12 May 2021
Location: Durham
Posts: 18
Yeah I can see the pressure starts off around 4500 then was hitting about 13000 before dropping and going into limp and was hitting 18000 early before hitting limp mode think it just hit 19000 one one try aswell. As soon as I go full throttle and it accelerates it goes into limp every time. Feels like it’s pulling fine but just constantly dropping into limp mode
16th May 2021 3:50 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 5049
Test ideally should be done under load for this type of fault, but the fuel pressure should never drop whilst you are placing load on the engine. The VCV will initially read higher than the PCV, but as the power curve increases the PCV should catch up and eventually pass out the VCV reading. At idle, you should be seeing fuel pressure of around 23,500 kPa to 25,000 kPa (fluctuating!) and the VCV and PCV at around 20% and 14% respectively.
On hard acceleration (load) the the fuel pressure will continuously rise from 24,000k kPa to around 160,000 kPa if you keep pushing! Looking at your screen shots there seems to be nothing wrong with those values, but they should be recorded under load until the fault is triggered. In any case, you will need to eliminate any possible issue with the low pressure side. A pressure gauge on the schrader valve will quickly tell you if the hpfp is being starved, indicating either a problem with the lpfp, the filter, or both. Again, under load whilst driving if you can monitor the gauge!
Ignore the "fuel rail pressure sensor" in IID and select "fuel pressure" instead. Also, if you have a look in the Wiki/maintenance there is a diagnosis provided by Robbie which will take you through each step in the diagnostic testing process. yµ (idµ - eAµ) ψ=mψ
16th May 2021 10:48 pm
Rossi84
Member Since: 12 May 2021
Location: Durham
Posts: 18
Thanks for all your help, got this sorted was the HPFP, fitted a new low pressure pump aswell as there was brass in the tank from the pump failing, all replaced and good at the moment, really appreciate all the help.
Only problem now is I have a strange slight either burning oil or coolant smell in the cabin at times from the vents and can’t figure out where it’s coming from as can’t find any leaks!
11th Sep 2021 9:57 pm
Luan9944
Member Since: 10 Dec 2023
Location: Brazil
Posts: 4
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