For some time now, I've had a throttle that was less than smooth. Unless I would apply the throttle very gingerly, the engine response was jerky, almost as if the butterflies were opening slowly, then suddenly opened a large amount. It made driving difficult, especially around town or in traffic when transitioning from small throttle opening to moderate. The power at WOT seemed OK, though. I chalked it up to similar reports on this board following the ECU reflash campaign (to correct a problem with the ability of the ECU to communicate with certain smog checking equipment), and/or the US throttle map, which people suspected had less than optimal mixture spots in it as compared to its EU counterpart. Basically, then, I was resigned to live with it. It was not "bucking bronco" bad, mind you, just not fun to drive. Perhaps on a lighter car the effect would be worse, but the M5 is fairly heavy and has a refined drivetrain, which probably ameliorated the issue to some extent.
Fast forward to last month. As my odometer turned past 114k miles, I started to worry about my fuel pump giving out and stranding me unexpectedly. I use my car as a daily driver and I wanted to minimize the chances of this happening to me. I have seen reported failures of fuel pump on this board happening around the 100k mark, so I figured I was on borrowed time.
I thus had the fuel pump changed recently. This is no small expense. The part itself is quite expensive and there is obviously some labor involved. I did not want to do this myself due to the inevitable fuel spillage and fire risk.
To my surprise, there was an immediate improvement in driveability. Throttle inputs now are smooth, no matter how quickly or slowly I open the throttle. There is more seat-of-the-pants feeling mid-range torque. The engine responds smoothly, more strongly, and has returned to being a pleasure to drive. I theorize that my old fuel pump, while it had not gone bad as in non-functional, had been marginally performing and possibly erratically delivering pressure or providing low or less than optimal pressure.
I had a similar experience with my M3, a far newer car which exhibited similar, though greatly worse symptoms that my tech could not track down at first. Like that car, there were no codes thrown, but the driveability definitely suffered. Having eliminated all the other possible causes, I insisted my tech/dealer change the fuel pump. Even though the car at the time was still under warranty, I offered to pay for the job if the swap did not solve the problem. Turns out I was right; a pump swap solved the problem. To their credit, though I suggested the fix, the dealer insisted they would pay for the work even if it turned out I was wrong.
Like the other car, my M5 did not exhibit any symptoms other than the less than smooth throttle response. It threw no codes. It started fine and ran fine, and accelerated strongly at WOT. If you are experiencing driveability issues and have high mileage, consider a fuel pump change. BTW, I changed the fuel filter not all that long ago (15-20k miles ago, maybe), but swapped in a new one anyway with the fuel pump change. I doubt the improved throttle response was due to the filter change alone. I hope reporting this experience helps others. If you experience similar problems and results, please post them. :M5launch:
Fast forward to last month. As my odometer turned past 114k miles, I started to worry about my fuel pump giving out and stranding me unexpectedly. I use my car as a daily driver and I wanted to minimize the chances of this happening to me. I have seen reported failures of fuel pump on this board happening around the 100k mark, so I figured I was on borrowed time.
I thus had the fuel pump changed recently. This is no small expense. The part itself is quite expensive and there is obviously some labor involved. I did not want to do this myself due to the inevitable fuel spillage and fire risk.
To my surprise, there was an immediate improvement in driveability. Throttle inputs now are smooth, no matter how quickly or slowly I open the throttle. There is more seat-of-the-pants feeling mid-range torque. The engine responds smoothly, more strongly, and has returned to being a pleasure to drive. I theorize that my old fuel pump, while it had not gone bad as in non-functional, had been marginally performing and possibly erratically delivering pressure or providing low or less than optimal pressure.
I had a similar experience with my M3, a far newer car which exhibited similar, though greatly worse symptoms that my tech could not track down at first. Like that car, there were no codes thrown, but the driveability definitely suffered. Having eliminated all the other possible causes, I insisted my tech/dealer change the fuel pump. Even though the car at the time was still under warranty, I offered to pay for the job if the swap did not solve the problem. Turns out I was right; a pump swap solved the problem. To their credit, though I suggested the fix, the dealer insisted they would pay for the work even if it turned out I was wrong.
Like the other car, my M5 did not exhibit any symptoms other than the less than smooth throttle response. It threw no codes. It started fine and ran fine, and accelerated strongly at WOT. If you are experiencing driveability issues and have high mileage, consider a fuel pump change. BTW, I changed the fuel filter not all that long ago (15-20k miles ago, maybe), but swapped in a new one anyway with the fuel pump change. I doubt the improved throttle response was due to the filter change alone. I hope reporting this experience helps others. If you experience similar problems and results, please post them. :M5launch:
showed it to be likely down to a fuel supply issue, somewhere. I therefore resolved to revamp the fuel system, and did : fuel pump (uprated Walbro 255, it did benefit that car over standard when going up in power), fuel pump power supply fix (taking the power feed for the pump from an alternative direct 12V feed, that meant the pump actually got a full 12V feed), reconditioned injectors, showing an even, proper flow over all 5, fuel filter, fuel pump relay, just in case, and a couple of wiring mods where things could go Pete Tong, especially the 'yellow' connector... I had all the hosing checked and connections remade but there was nothing to note.
