Friend plugged this up and it came up with p0088 fault code. To high pressure in fuel rail. Sensor gone bad? Bad batch of fuel upset it? Would prove the hpfp belt isn’t at fault.
10th Jul 2022 3:58 pm
Voxx
Member Since: 09 Jul 2022
Location: Kent
Posts: 6
Update on this, toothed pulley on the pump taper shaft was loose. Nut had loosened to the point of being able to undo it by hand! Any one seen this before?
14th Jul 2022 7:16 pm
Iknutis
Member Since: 22 May 2022
Location: Molde
Posts: 11
Final update from me, after about 8months with this issue.
Read the guide here, measured 2.5psi on the schrader so figured it had to be something wrong with the LP-system.
Changed the filter, the in-tank pump twice, the filter bracket, the return-line, but never got above 4psi on the schrader.
In-tank pump has never drawn above 3A, not even when connected directly to a battery on the floor next to the tank.
After all this, I thought it had to be on the HP-system, even tho the guide stated otherwise.
So I changed the hpfp, and that made coldstarts much much easier. Still same p0087-00 error tho. Ok when cold, frequently when warm.
Changed the fuel rail pressure sensor, although nothing in the live values or error codes pointed toward it.
Now the car runs great, with 4psi on schrader at idle and barely positive pressure when revving.
So dont’t let the numbers from Robbie fool you, not all Discos have the same numbers.
It’s a great guide for understanding how the lp-system works, but your car may never get above 4psi on the schrader like mine.
20th Sep 2022 9:29 pm
PerthDisco
Member Since: 21 Jun 2010
Location: Perth
Posts: 85
Just to confirm some values here with the group;
With engine off and jumping the relay I get the following;
Ive swapped the relays around and still get this at engine idle.
Should it not be at 6.6psi which I can replicate when jumping the relay?
Thanks
5th Mar 2023 1:29 am
bensla
Member Since: 02 May 2023
Location: Trowbridge
Posts: 138
I’ve just been testing my LP pump at the schrader valve. It’s about 6.2psi during the ignition priming stage but then drops to about 4.8psi at idle. Does this suggest an issue? I’m getting low fuel rail pressure codes and full limp mode - even under light load.
12th Sep 2023 9:27 pm
jenseneverest
Member Since: 12 Jun 2017
Location: somewhere
Posts: 760
from robbies guide
Quote:
If the needle is unsteady then the pump may be struggling or even missing some impellers. If the pressure drops significantly when the throttle is pressed then you know the LP system is finding it difficult to cope with the demands of the HPFP, which runs at scary pressures
13th Sep 2023 11:18 am
bensla
Member Since: 02 May 2023
Location: Trowbridge
Posts: 138
I guess the question is how much is too much, especially just at idle. Also is there any logic in the assumption that if the pressure is ok at priming stage but not at idle then the issue might be more to do with restricted flow than the LPFP itself? I think there are some mesh filters somewhere near the pump in addition to the actual filter that might be worth checking is that right?
13th Sep 2023 11:47 am
jenseneverest
Member Since: 12 Jun 2017
Location: somewhere
Posts: 760
I would expect the pressure to drop once you move from priming to engine running, dose it struggle to maintain 4psi when you rev it up ? Genuine fuel filter is a must IMO, have had issues in the past with cheap ones..... sadly my diesel is going next week, im currently rebuilding a v8 petrol
14th Sep 2023 12:41 am
bensla
Member Since: 02 May 2023
Location: Trowbridge
Posts: 138
Just jumped the relay and collected the fuel through the schrader. 280ml in 60 seconds. Think that explains the issue right?! If it was doing this for ages it might also explain why it had a HPFP replaced recently if it’s been fighting against this poor flow.
14th Sep 2023 9:24 am
bensla
Member Since: 02 May 2023
Location: Trowbridge
Posts: 138
In case anyone was wondering, I ended up dropping the tank with the expectation of replacing the low pressure pump. I tested the flow at the hose out of the tank - no issues at all 750ml in 20 seconds.
I hooked it all back up and tested again at the schrader valve but this time instead of using a bike pump hose on the valve I disconnected the connector to the side of the valve and pushed a hose onto the end of the line. Same high flow here too. So a lot of wasted time just because I was using the schrader valve and bike pump hose to measure flow.
The valve or bike pump connector must not be allowing sufficient flow to test it! Hopefully this will stop someone else making the same mistake. At least I’m pretty confident it’s an issue on the high pressure side.
20th Sep 2023 7:36 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4618
Yes on a low pressure system such as this the schrader valve needs to be removed using the same tool as you would for a tyre valve! You then just slip a fuel line over the stub and clamp it with a jubilee!
But I guess you know that now. yµ (idµ - eAµ) ψ=mψ
20th Sep 2023 8:04 pm
bensla
Member Since: 02 May 2023
Location: Trowbridge
Posts: 138
Heh yeah all good learning experience eh!
20th Sep 2023 8:08 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4618
What is your fuel flow? (lt/min)yµ (idµ - eAµ) ψ=mψ
20th Sep 2023 8:22 pm
bensla
Member Since: 02 May 2023
Location: Trowbridge
Posts: 138
I haven’t done a full minute and only very crudely guessing based on marks on a milk bottle but it’s about 300ml in 10s.
20th Sep 2023 8:34 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4618
You need to see at least 1.5 l/min as a baseline measurement, it can still run on very slightly less but I'd replace the pump if it's below 1.5 l/min.
In another of your posts elsewhere, I did suggest to you that if you pull the fuse on the lpfp the car should still drive ok if the lp side is working properly. A successful test drive in this condition could also be taken as an indication of a healthy HPFP!yµ (idµ - eAµ) ψ=mψ
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