Low MPG

[ZerokoolRCZ]

OMG this engine, seems like every week I'm reporting something on here,
The other week I had come on here with engine light due to P0087 High Pressure fuel circuit pressure (pressure to low) was able to clear code with Carly, but has come back, now both fuel pumps got changed 2 years ago, so don't know if could be a fuel filter issue? but have seen that you have to drop fuel tank to get to it

Since this fault I have seen the MPG go down, even after deleting the code, I normally get around 40mpg on average going to work, now its down to 28mpg, any idea as to what could be the issue? I have read that a faulty MAF sensor can be a reason.

Any ideas?

Thanks

 

[EddieJ]

Only throwing a few thoughts out there.

OBD based,
Take a reading of your fuel pressure to know what it is actually at, if it’s stable, low or high etc. about 700+ psi is decent.
(nb: recon pumps have been mentioned on here as having 10-15k mile lifespans, don’t know if you went new or refurb).
Read the long term and short term fuel trims, and the stoichemetric value to see if the lambda sensors are working effectively and they near match each other. If all over the place as if they are trying to matching to something could be a sign of injector issue or incorrect fuelling ratios.

Visual and physical checks.
Check for vacuum leaks, vac solenoid is at the rear of the engine below the inlet manifold and follow the pipes as best as possible.
Also check for air intake air leaks, charge air cooler etc that may be getting in unmetered, the pipe as it meets the turbo from the air box has a tendency to split over time/age.

 

[ZerokoolRCZ]

Hi Eddie,

thanks for the reply,

ref the pump, replaced both and the high pressure one was new at £600,

I will be doing the water crossover pipe soon so will check the solenoid when I take the inlet manifold off, will check other parts for leaks at the weekend,

Engine light came back on tonight

 

[ZerokoolRCZ]

Hi, so did a test with the Carly at lunch
At idle, 728 psi, at 1600rpm it was 712 psi, so looks ok there, I may try at higher rpm

 

[EddieJ]

Don’t know if you can record a log with your Carly device but if not a passenger watching could keep an eye on it and take the car for a good run through smooth and spirited to see if the psi drops away, a couple of miles should do it. When you do boot on it will drop off but will quickly recover. It would be good to rule that out, especially having only changed them. You can also physically measure the outside of the hpfp to see if it has dropped its fluid level, search the forum for the actual numbers but I think it’s 27mm on its worst with 11-13 good and 15mm+ may be over filled which can leave no room for temperature related expansion. Measurement is taken down the centre of the round ‘doughnut’ on the pump. There are also a few good YouTube vids about on refurbishing that go through the numbers, measuring, resealing and refilling.

 

[ZerokoolRCZ]

Don’t know if you can record a log with your Carly device but if not a passenger watching could keep an eye on it and take the car for a good run through smooth and spirited to see if the psi drops away, a couple of miles should do it. When you do boot on it will drop off but will quickly recover. It would be good to rule that out, especially having only changed them. You can also physically measure the outside of the hpfp to see if it has dropped its fluid level, search the forum for the actual numbers but I think it’s 27mm on its worst with 11-13 good and 15mm+ may be over filled which can leave no room for temperature related expansion. Measurement is taken down the centre of the round ‘doughnut’ on the pump. There are also a few good YouTube vids about on refurbishing that go through the numbers, measuring, resealing and refilling.

Thanks again Eddie