Screaming fuel pump

[HFStuart]

On my throttle body conversion I've got a Facet type pump as a lift pump to the swirl pot then a sytec high pressure pump to feed the injection. The pump is mounted so it gravity primes and draws from the bottom of the swirl pot and pumps to the fuel rail via a filter. Return from the fuel line is through a pressure regulator set to 3 bar and then return to the swirl pot.

The pump always had the odd screech on start-up - recently it started doing it continuously. This is not the usual fuel pump whine but a really loud screech noise.

I assumed I'd got some crud in the pump and knackered it so I bought a replacement. Guess what? Same noise though now intermittent again.

I've checked the filter and it's free flowing. I've also checked the lift pump and it's keeping the swirl pot topped up.

Any bright ideas?

[lukasdeopalenica]

I had a very similar case. The scream was caused by fuel mixed with air bubbles that the pump was pumping. I had no idea how the bubbles were created somewhere in the fuel return lines and were flowing directly to the swirl pot just under the pick up. Suddenly the effect just disappeared.

[HFStuart]

A bit more investigation and I've found the noise is NOT the pump. It's the pressure regulator resonating.

A new regulator is another £100 or so. So before I replace it I'll give FSE a call and see if they've got any ideas. It's just a spring and a diaphragm so I'm not sure if it can go wrong - I'd have thought it either works or it doesn't.

[HFStuart]

Now solved. I spoke to FSE, they could not have been more helpful and told me that if the fuel passes over the diaphragm too fast it can causeit to resonate.

New models have a restrictor fitted to slow the fuel down (a perforated brass bush that fits over the valve seat). They popped one in the post to me FOC.

Now fitted and the noise has gone. Good - and thanks to the guys at FSE!