 | Home > Puma (Tdci) > Loss of Power - VCV or Fuel Pressure Regulator |
 
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Fuel Pressure Regulator...per the picture attached. Thought great easy fix I hope....cleared the code and issue is still there but the code has not appeared again. Popped the hood (bonnet) to look at the fuel rail and noticed a ton of wet diesel soot on the intake manifold. No idea if this is related. Pics attached too. Not sure what to look at to diagnose the issue - any recommendations?
| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 21044  
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I was wondering if it was the Pressure Relief Valve, which is VCV associated, but I’m unsure if it would run at all if that had gone.
Blackwolf on here, may possibly be along with some details on these type of faults, but if the PRV goes, you can only but replace it. But it isn’t that common. Did you replace the VCV or just presumed? have you checked around the injectors that they aren’t wet?  ____\We|Will|Win/___
____/🇬🇧🇺🇸\____ _//*⛽️🛢️⚙️🧰*\\_ Last edited by custom90 on 8th Oct 2025 6:27pm. Edited 1 time in total |
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7th Oct 2025 8:20pm |
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| irishhawk11 Member Since: 07 Mar 2022 Location: In the Pub crying due to defender issues Posts: 36  
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Strange picture, as the suit is all around the air intake manifold.
I don't believe it is the VCV or PRV as it is clean but anyways, have a closer look at the PRV. As mentioned this needs replacement when it was triggered, bit again this has a fuel return line and shouldn't spray fuel. I would also recommend to look around the injectors. |
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8th Oct 2025 8:02am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 18058 
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On a 2.4 the VCV is the fuel rail pressure regulator, there is no other way to modulate rail pressure.
Do not confuse the pressure release valve on the rail with a regulator, the PRV is simply there to protect the injectors etc from excessive rail pressure in the even of VCV malfunction. The PRV is a non-resettable valve, once popped it must be replaced (although it is not unknown for them to leak). |
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8th Oct 2025 9:26am |
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| MGRGPGBG Member Since: 19 Dec 2017 Location: New York Posts: 74  
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I have not changed the VCV - I did put a new one in about 30k miles ago when I built my truck.
Will pull cover and check injectors - they should be OK as I had new seals and washers installed at a service last winter. Any idea on the soot issue?
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9th Oct 2025 12:27pm |
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| MGRGPGBG Member Since: 19 Dec 2017 Location: New York Posts: 74
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If the PRV did pop, would the error code come back after I cleared it? I have been driving a few days and the issue persists but no codes on my reader now.
Also noted that this happens only when the engine is at running temperature. I get a puff of white smoke out of the exhaust when I feather the throttle to get it out of this loss of power condition, or if I can get enough RPM's to shift up and then back to normal running.
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9th Oct 2025 12:31pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 18058
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If the PRV had popped you would permanently experience extremely low fuel rail pressure and would not be able to drive normally. It is less certain that you'd get a DTC, since the 2.4 fuel system is very poorly covered by diagnostics.
If the PRV was leaking you may still get reasonable running but with incorrect rail pressures. You oily gunk looks to me more like it might indicate a leak in a boost pipe, which is unloading oily induction air over the manifold. It doesn't look to me like a fuel leak from above. Probably 90% of 2.4 Puma fuel-related problems are due to the VCV malfunctioning. Generally any kind of misfire, erratic idle, lack of power. or poor performance particularly when sudden changes in engine demand are made, especially if there are no DTCs, will be down to the VCV. There also seems to be a growing and disturbing trend for new VCVs straight out of the box to be defective. Bearing in mind how (relatively) cheap the VCV is, it is usually a sensible first step to change it, since in most cases - but not all - it will the problem. |
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9th Oct 2025 2:02pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 21044
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I think the most likely DTC that would be logged would be fuel rail related due to low pressure malfunction, provided it got to at or below the threshold that it would kick in to trigger logging the code.
Check the Turbo vanes are free and the actuator is working as it should too, yes, again a big malfunction would create a DTC for this, but it doesn’t always get to the stage of triggering a DTC. White smoke iirc means slightly on the lean side on fuelling, blue tends to be oil burning which is not good at all! Black, rich on fuel. You do get more steam in cold / wet weather as well, on cold starts in very cold weather a little more smoke, but will soon clear. You really could do with seeing live rail pressure, but you’d need the expected parameters to compare against. I expect you can find this on here or online. ____\We|Will|Win/___ ____/🇬🇧🇺🇸\____ _//*⛽️🛢️⚙️🧰*\\_ |
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9th Oct 2025 9:00pm |
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| MK Member Since: 28 Aug 2008 Location: Santiago Posts: 2512  
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White and smelly smoke indicates excesive/unburnt diesel. Puma 110" SW
............................................................. Earth first. Other planets later |
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9th Oct 2025 9:14pm |
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| MGRGPGBG Member Since: 19 Dec 2017 Location: New York Posts: 74
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Update on this post - the issue has gone away for a while now. I am wondering if I filled up with a bad batch of Diesel and after three tanks that it cleared out the bad fuel? I did run my tank down pretty low on the last fill up and perhaps that is all it was. Next service will swap out the fuel filter to be safe. Opinions / experiences? |
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29th Oct 2025 12:29pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 21044
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Unfortunately that’s how the VCV can act, then it can and does come back, seems fine for a bit but can start again.
How do you find power in 5th gear? Based on the pics you posted there is a minor boost leak there too, on the intake manifold. In the WSM you can find the torque settings Ti ensure the fixings are tightened to spec if they’ve slightly loosened. If that doesn’t do the trick then may need taking apart and refitting, but the manifold bolts can loosen over time, I’ve had that and will result in a minor boost leak and oily deposits around there. Just one fixing will do it. ____\We|Will|Win/___ ____/🇬🇧🇺🇸\____ _//*⛽️🛢️⚙️🧰*\\_ |
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29th Oct 2025 5:50pm |
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| MGRGPGBG Member Since: 19 Dec 2017 Location: New York Posts: 74
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5th gear power good / normal. I had this happen maybe 2 years ago and when I swapped out the fuel filter the issue went away. Very odd for sure. Thanks on the leak tips - will start hunting that one down next. |
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29th Oct 2025 6:18pm |
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| Linds Hanson Member Since: 16 Jan 2021 Location: Cornwall Posts: 540
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The 2.4 doesn't seem to log a fuel pressure fault even when the vehicle is undriveable! We seem to have more vehicles turning up with restricted flow from the tank either from diesel algae or general filth in the fuel blocking the pickup intermittently. Also the plastic filter head can become blocked or cracked allowing air into the system.
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29th Oct 2025 6:38pm |
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| MGRGPGBG Member Since: 19 Dec 2017 Location: New York Posts: 74
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Thank you - will look into the fuel filter head too.
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29th Oct 2025 7:00pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 21044
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I’d recommend sticking only to Genuine LR fuel filters too, others can be problematic.
Plus prime them, I.e. fully fill with diesel before fitting. If you get air in there Pumas can be a pain in the backside. ____\We|Will|Win/___ ____/🇬🇧🇺🇸\____ _//*⛽️🛢️⚙️🧰*\\_ |
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30th Oct 2025 5:18pm |
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