Member Since: 07 Mar 2022
Location: Feldkirch
Posts: 12
Fuel rail pressure
Hi everyone,
I'm dealing with a strange fuel rail pressure issue on my 2.4 Puma Defender and would really appreciate your input.
Problem: When idling – mostly when cold, but also sometimes when warm – the accelerator seems to stay slightly engaged on its own. The revs don’t drop cleanly, and it feels like the throttle hangs a little, even without touching the pedal.
Observation: I connected diagnostics and recorded the fuel rail pressure. You can see it in the screenshot below.
Most of the time during idle, the pressure fluctuates heavily. There’s a lot of instability in the values, which seems unusual for idle.
⚠️ Note: The high peak (226.8 bar) was caused by a short acceleration – not during idle.
What I suspect:
VCV (Volume Control Valve) not regulating properly?
Or a faulty fuel rail pressure sensor giving erratic readings?
Additional info:
More noticeable when the engine is cold.
Vehicle is stock, no remap, except EGR
My questions:
Do the pressure fluctuations at idle look abnormal to you?
Can a bad VCV cause throttle-hang without a fault code?
Should I begin by cleaning/replacing the VCV or swap the pressure sensor first?
Thanks a lot in advance – looking forward to hearing your thoughts or similar experiences!
Cheers,
Benjamin
Click image to enlarge
15th Apr 2025 11:04am
andy63
Member Since: 30 Jun 2023
Location: north east
Posts: 707
My 2.2 fuel rail pressure fluctuates but 200 t 400 psi or more at idle if i remember correctly.. 3200 to 3700psi ish.. that's tick over..
On a cold start the rail pressure couldn't be up to 4500 psi ish dropping as the engine warms up..
15th Apr 2025 11:27am
blackwolf
Member Since: 03 Nov 2009
Location: South West England
Posts: 17729
The VCV on a 2.4 can cause all of those symptoms and all without DTCs. The VCV is notoriously fragile, is not serviceable, and is much more likely to be at fault than the sensor.
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15th Apr 2025 11:27am
