P0087 means fuel pressure in the rail is below what the engine computer asked for. It is most common on diesels, and it usually shows up as lost power or limp mode under load rather than as a rough idle. Get it checked before driving far. Indicative UK repair cost is £80 to £900.
On a common-rail diesel the pressures involved are well over a thousand bar, and the system is built in two halves: a low-pressure side that lifts fuel out of the tank and through the filter, and a high-pressure pump that squeezes it up to rail pressure. P0087 says the rail did not reach the figure asked for. It does not say which half is at fault, and the difference between the two is most of the money.
Can I drive with P0087?
Get it checked before driving far. Limp mode is the car protecting itself and it is worth respecting. The specific risk on a common-rail diesel is that a high-pressure pump which is wearing internally sends metal debris downstream, and once that has been through the rail and the injectors the job stops being a pump and becomes a pump, pipes, rail and injectors. If the car has gone soft on power, do not keep working it hard to get the miles done.
What P0087 means for your MOT
The fuel system items in the MOT are about leaks and security rather than pressure, so low rail pressure is not a defect in itself. The warning light is. For a diesel first used on or after 1 July 2008 the lamp is checked under section 8.2.2.2 of the DVSA MOT inspection manual, and for a petrol car first used on or after 1 July 2003 under 8.2.1.2. Either way, a lamp indicating a malfunction is a major defect.
Two things worth knowing that nobody tends to mention. A diesel short of fuel pressure usually smokes less than a healthy one, not more, so it can pass the opacity test comfortably and still fail on the lamp. And the smoke test needs the engine revved freely to its governed speed, which a car locked in limp mode may not manage, in which case the test cannot be completed at all.
What usually causes it
- A weak lift pump or in-tank pump. The low-pressure side. A high-pressure pump cannot make pressure out of fuel it is not being handed in the first place.
- A clogged fuel filter. The cheapest thing on the list and the most common on a car with an unknown service history, or one that has had a bad tank of fuel.
- A leaking pressure regulator. The metering or regulating valve on the high-pressure pump is supposed to hold the rail where it is told. A worn one bleeds pressure back to the tank instead.
- An injector leaking back internally. A single injector can dump enough fuel into the return line to stop the rail ever reaching target, and it will do it without obviously misfiring.
What it costs to fix in the UK
£80 to £900. A filter and the labour to fit it is the bottom of the range. A regulating valve sits in the middle. A high-pressure pump or a set of injectors is the top, and if debris has already been through the system the real figure goes above it, because everything downstream has to be replaced or cleaned.
Because the spread here is so wide, paying for a proper diagnosis first is the cheapest decision available. Our guide to what a car diagnostic costs in the UK gives you the going rate to compare against.
These are indicative UK ranges for guidance only. Actual causes and prices vary by vehicle, and a stored code points to a system, not always the exact part.
What to check first
- Change the fuel filter and inspect the old one. Cut it open if you can get at the media. Fine glittery metal in there means the high-pressure pump is coming apart, and that single observation changes the whole job.
- Compare actual rail pressure against commanded, at idle and under load. A rail that builds at idle and then collapses when you ask for power is a supply or regulator problem. One that never gets near target at all points further up the list.
- Test injector back-leak. Measuring the return from each injector individually names the one that is leaking. It needs a workshop and a set of test pipes, and it is the only honest way to avoid replacing a full set on suspicion.
- Look for air getting into the supply. A weeping filter housing seal, a perished rubber line or a loose hand-primer will let air in, and an engine drawing air gives these exact symptoms with every component in good order.
Related codes
- P0300, random or multiple cylinder misfire. On a petrol engine, fuel starvation across all cylinders shows up as a random misfire rather than as this code.
- P0299, turbocharger underboost. The other common reason a diesel loses power and drops into limp mode, and the two are regularly confused by symptom alone.
- P2002, diesel particulate filter efficiency low. The third code diesel owners see most, and one that can be blocked from clearing while this fault is stored.
Get it narrowed down before you spend
A stored code tells you which system is unhappy, not which part has failed. If you want it narrowed down before you spend anything, send the code and your symptoms and a mechanic will read them personally. Quick Diagnosis is £20, and if we can't help, you don't pay.
Written by the First Diagnostic mechanic. Over a decade in the trade: a VW-only workshop running diagnostics and electrical repair, then BMW-only through to full engine rebuilds. Now an independent all-makes workshop, plus building and wiring drift cars for competition, including trackside work as head mechanic. More about who reads your codes.