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Does this sound like a dying fuel pump?

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  • Does this sound like a dying fuel pump?

    Morning gents. I need to properly update my project thread soon, but life has been a bit mental and I’m now working mon to fri away from home. My A4 is waiting for a lurch so I had to get the CQ20v back on the road quickly. I did that about a week ago because I needed a car to do the 450km drive each way.
    So on Sunday evening I did the drive. The car has a number of things I need to sort out but they’re almost all forgivable for now. The thing that made the drive a bit tense is a load of juddering. It feels to me like fuel isn’t getting through at times. Most of the time when I was cruising at 80 to 120km/h it was ok, and when I overtook at higher speeds it was mostly ok, although the car didn’t have as much power as it should have. The real problem was when I had to slow down and then accelerate again. Trying to accelerate without high revs often resulted in hesitation, like juddering. Erm. Like the power was coming on-off-on-off-on-off. The car definitely did not like trying to accelerate with low revs and didn’t like me trying to drive at 60km/h (40mph) in 5th (its a 5 speed box).
    Occasionally while cruising I would feel a flicker of life, like a hint of the car’s proper power. It still did the 4.5 hour drive and got me here. It wasn’t ideal though.
    I’m confident I have a spare fuel pump at home and my missies is looking for it to post down to me so I can fit it before grading back up on Friday evening. I’d really appreciate some input though to find out if this really does sound like a pump issues
    cheers
    --------------------------------------------------------------------
    1990 CQ20v
    2001 3.0 B6 A4 Avant Quattro Sport

  • #2
    Morning Fella. I hate to say it dose not sound like fuel pump to me. If the pump had a loose wire then maybe it would act in this way. Can you see if the pump is loosing power when your driving. Dose the car have an alarm fitted and how old is it. Check loose contact to fuel pump relay. Have you had a look at the injectors wires. Not much help but I hope you get to the bottom off it. regards Lynn

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    • #3
      Fuel delivery is fairly easy to check. You are looking for a certain quantity in a certain time and your fuel pressure regulator takes care of the pressure. From memory it is a case of disconnecting the fuel delivery line at the fuel rail and directing that into a plastic bottle/measuring jug. Get a jumper wire in the fuse box to make the pump run and see how much fuel comes out. Run the pump for 15 seconds and hope more than 600ml of fuel.comes out.

      My Cq20v did have a problem with the power supply to the pump, that was never traced but I fixed it by running a new wire from the relay in the fuse box, under the carpet to the pump. Loads easier than trying to find the break in the loom!

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      • #4
        Is the fuel filter new?
        This is the exact symptoms when my tractor fuel filter is getting blocked!

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        • #5
          Knock sensors?

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          • #6
            Thanks lads
            Originally posted by LSG View Post
            Morning Fella. I hate to say it dose not sound like fuel pump to me. If the pump had a loose wire then maybe it would act in this way. Can you see if the pump is loosing power when your driving. Dose the car have an alarm fitted and how old is it. Check loose contact to fuel pump relay. Have you had a look at the injectors wires. Not much help but I hope you get to the bottom off it. regards Lynn
            How would I check if it's losing power while I'm driving mate?
            No alarm. Had an old immobilizer ages ago but that was removed when I bought the car.
            I'll check the relay. Hopefully the fuse box isn't labeled in French (car was originally French)
            I'll also check the injector wires, cheers.
            My gut feeling is that it isn't an electrical connection issue because the issue ie related to how much welly i'm giving it and how high the revs are relative to how fast i'm trying to go (problems doing slow speed in 5th for example)

            Originally posted by steve briance View Post
            Fuel delivery is fairly easy to check. You are looking for a certain quantity in a certain time and your fuel pressure regulator takes care of the pressure. From memory it is a case of disconnecting the fuel delivery line at the fuel rail and directing that into a plastic bottle/measuring jug. Get a jumper wire in the fuse box to make the pump run and see how much fuel comes out. Run the pump for 15 seconds and hope more than 600ml of fuel.comes out.

            My Cq20v did have a problem with the power supply to the pump, that was never traced but I fixed it by running a new wire from the relay in the fuse box, under the carpet to the pump. Loads easier than trying to find the break in the loom!
            I'll give that a bash too. cheers. Again, I wonder if it could be that though when it's not fully "random"?

            Originally posted by Tractor Dave View Post
            Is the fuel filter new?
            This is the exact symptoms when my tractor fuel filter is getting blocked!
            It was new a couple of years ago but i've barely driven the car since. I think I ran out of petrol at one point but can't recall if that was before or after the filter change. Might be worth changing the filter again anyway, just in case.

            Originally posted by Bowie69 View Post
            Knock sensors?
            This has just made me go "hmmmmmm". Good call. I'm not sure how to diagnose those though. I think it's just a case of replacing them. I have a 2+2 adapter but no VCDS here. and limited tools. ah nuts.

            On a short trip into work (town driving only) I didn't notice any issues. Do the knock sensors only come into effect when the engine's warm? Or am I away on a tangent there?
            --------------------------------------------------------------------
            1990 CQ20v
            2001 3.0 B6 A4 Avant Quattro Sport

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            • #7
              Forum diagnostics!......always tricky!

              …..but from your description could it maybe be a HT misfire...…..a really bad one so maybe the king lead? Worth checking the ends for corrosion, easy enough to see.

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              • #8
                To check your pump when driving your need a small bulb holder and bulb make the wire's so it runs from your fuel pump wires to the front of the car so can see it. Connect one to the pumps live side and the other to the earth. Go out for a drive if your loosing power you see . So it maybe the live or the earth you loosing. You can fit a second earth strap from pump to car body

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                • #9
                  Sorry I posted before I finished. After doing the earth from pump go out for a drive again. Hope this helps a little but you see what's happening with the power to the pump this way. Good luck fella. Regards Lynn

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                  • #10
                    Originally posted by John. View Post
                    Forum diagnostics!......always tricky!

                    …..but from your description could it maybe be a HT misfire...…..a really bad one so maybe the king lead? Worth checking the ends for corrosion, easy enough to see.
                    Very True John
                    I just replaced the HT leads, so unless I have a dud lead I think they should be OK. If I haven't resolved things by the time I get home, I'll test with the old lead(s) to see if it makes a difference.

                    Originally posted by LSG View Post
                    Sorry I posted before I finished. After doing the earth from pump go out for a drive again. Hope this helps a little but you see what's happening with the power to the pump this way. Good luck fella. Regards Lynn
                    Aha. I see what you mean Lynn, cheers. I'll do that to see if it is indeed an issue with the live or earth to the pump.

                    That's a couple of days of moderate driving and it has been behaving, Even doing 120km/h coming back from the airport monday night it was ok. But I didn't boot it to get up to that speed.
                    --------------------------------------------------------------------
                    1990 CQ20v
                    2001 3.0 B6 A4 Avant Quattro Sport

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                    • #11
                      For knock sensors, loosen, and re-torque, 22nm from memory? But do check....

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                      • #12
                        …….what's happening?

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                        • #13
                          well... It's not the pump. I pulled the old one out and went to put a "new" one in (from a '95 V6) but it was much thicker so I'll need a cage/basket for that if anyone has a spare? I dropped the bigger pump in without a basket for a test run and it may have been mildly better but the issue still remains. Unfortunately, my handheld code scanner is in the back of my A4, which is still in the garage getting the new clutch and flywheel. I have the 2x2 adapter but no code reader and to be honest I don't even know if it will work with such an old car. I'm basically home friday night to sunday afternoon and had 1000 other things to do so I had limited time to investigate further. From test driving it and forcing the issue to happen i'm more and more inclined to think it's the knock sensors. i found another thread where someone said that the newer sensors can be used, so i'm heading off in the afternoon to see if the local motor factors has the Bosch parts I need. I have a bunch of tools in the back of my car but no torque wrench so I won't be able to torque it properly. I'll need to get professional help for that, or buy another bloody torque wrench (couldn't find mine when leaving the house yesterday).
                          I never intended for this car to be used for big miles but here we are. and when the A4 is back today or tomorrow i'm pretty sure my missus will want to keep it because she doesn't like driving the coupe. It takes too much 'work' to drive it in her opinion
                          --------------------------------------------------------------------
                          1990 CQ20v
                          2001 3.0 B6 A4 Avant Quattro Sport

                          Comment


                          • #14
                            Originally posted by Bowie69 View Post
                            For knock sensors, loosen, and re-torque, 22nm from memory? But do check....
                            Mac. F*cking. Daddy!
                            It was the knock sensors, or one of them at least. Audi said they couldn't order them for me (WTF?) but I found Bosch part numbers for the newer "doughnut" sensors in another thread. In the interest of helping anyone else who comes across this thread in the future:

                            Original part numbers:
                            54 905 377 B
                            054 905 377 C

                            Newer doughnut sensor part numbers:
                            Bosch 0261231038 (green)
                            Bosch 0261231036 (blue)
                            +
                            2 bolts (M8x1.25x28mm (audi part number N0102336)). I used 25mm length and a couple of washers.

                            So they are indeed a right ****er to change. I unbolted the fuel regulator and pulled it to the side, then took off the bracket that was holding it. That gave me some access to the rear sensor. After cocking about with a spanner for a while, I cut the cable close to the sensor and dropped a vortex socket over the top (deep socket would do). Fitting the new one wasn't too bad. I had to use a couple of extensions on the socket and an elbow joint. Got it torqued to 20nm though.
                            The front one worse. Shame I didn't know about this when i changed the radiator and A/C condenser a month ago! Again, I cut the cable as close as possible to the sensor, and dropped a vortex socket over the top. putting the new one in was fiddly but I got there. I had to use the extensions and elbow joint, with the extension pushed through part of the radiator plastic shrowd/cowling thing. The space where one of the rad hoses passes through. that gave me enough of an angle to just about use the torque wrench.

                            The difference driving was really noticeable. I guess because it was garaged for 18 months I forgot was it was supposed to be like. But the power is smoother, there's a lot more of it and fuel consumption is lower. It sounds like a shouty 5 pot should do when I'm overtaking slow people. that's the main thing

                            Thanks for your thoughts and tips gents.

                            And now I'll go post a separate thread about how a little plastic guide wheel in the window mech fell apart and left me wet in a car wash!
                            --------------------------------------------------------------------
                            1990 CQ20v
                            2001 3.0 B6 A4 Avant Quattro Sport

                            Comment


                            • #15
                              Mate that's great news. Pleased for you. Happy driving . kind regards Lynn.

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