Low pressure in fuel rail??

[tester10]

Hi. My 2013 E-class CDI (99000 miles) went into 'limp mode' - only 5 gears - and the EML came on. Took it for a scan, which said "low pressure fuel rail". It was still performing quite well, other than the restriction of only having five gears. That day I was due to tow a light trailer on a 250 mile round trip, which I did with no performance issues. Could it be that the pressure sensor is faulty and telling 'porkies'? I would expect to have performance problems if the fuel pressure was actually low as indicated. Any suggestions?

 

[Stratman]

I'd say the next step is to have the fuel rail pressure measured. Take it to a good independent with the appropriate equipment, the pressures involved are very high (4,000 to 5,000 psi). The sensor itself could be faulty as could the pressure regulator. Both are simple replacements but it could also be an early symptom of impending pump failure. Unlikely, but an hour in the garage will work out cheaper in the long term than throwing parts at it.

 

[mersum1es]

Low rail pressure won't usually put it limp, it will cut out engine. Unless it is not plugged or giving implausible reading and it is ignored (thus fault code). Read a live data, or get is scanned by proper intrument (SDS)

 

[tester10]

I'd say the next step is to have the fuel rail pressure measured. Take it to a good independent with the appropriate equipment, the pressures involved are very high (4,000 to 5,000 psi). The sensor itself could be faulty as could the pressure regulator. Both are simple replacements but it could also be an early symptom of impending pump failure. Unlikely, but an hour in the garage will work out cheaper in the long term than throwing parts at it.

Thanks. I will try to get the pressure tested and get back to you.