Hi all,

I have a lovely 1988 XR3i with MFI K-Jetronic, and have a strange fuel pump issue

The car will start, run and perform faultlessly, under all conditions, whether hot or cold etc

However, after driving the car for around 5-10 miles, the fuel pump becomes noisy. I'm convinced it is sucking in air as the noise will come and go erratically, and when grabbing the high pressure line out of the pump between my fingers when the noise is present, you can feel high frequency vibrations. Those vibrations are not there when the noise isn't. The noise is significant, and spoils an otherwise fabulous car, but has no effect on performance, fuelling, or starting. Just an annoying noise

For what it's worth, I have done the following

1) New Bosch fuel pump
2) Re-built mounting cradle with 3 x new rubber mounts, so pump fully floating and insulated and no chance of any resonance
3) New low pressure fuel pipe from tank to pump
4) Checked all tank vents are clear, and of course the fuel cap
5) Brimmed the tank to see if it has any effect, but none evident

Worth mentioning that removing the fuel cap has no effect, and so there is definitely no vacuum within the tank

When the noise is present, I have dropped the pump from it's mounts and 'moved around' No pulling or moving of the pump itself or squeezing the inlet fuel pipe has any effect on the noise

Leave the car an hour or so, the noise will subside until driven a few miles again. Even running the car static until the fans cut in will not cause the noise to happen, leading me to believe it's related to expansion and pressure/vacuum changes in the tank that occur through temperature changes

Out of desperation I am likely to try another pump on it, but don't hold out much hope !

Any suggestions

TIA