Fuel Pump?

[Chris32]

Hi all,

just installed a Bosch 040 pump to my car. It runs well, no hassles there, but it makes this noise every so often that makes me nervous.

At idle, probably once a minute or so every now and then it makes a very quick noise. Its like a suck/grind in one hit. Very weird. What could it be?

I have fitted the stock pump until I work out what it is.

The pump is new, and is sitting at the same height,maybe a few mm's lower?:confused:

[blind_elk]

I get the same in mine. I believe its something like the returning fuel is being dumped right beside the pump, and its hot, and the pump doesn't like pumping hot fuel. I have a fuel pressure gauge hooked up, and it gives a bit of a flutter every time this noise occurs.

[Chris32]

When does this happen with yours?

I only have noticed it after idling the car for a couple of minutes

Know how to fix this?

[blind_elk]

Yes, mine tends to do it after a warm start, and only apparent at idle. Since it happens even with a full tank, perhaps hard to believe its hot fuel causing this.

Had a chat with one of the guys where I got the pump, he's suggesting that with minimal clearance of the pump to the bottom of the tank (mine is set up with only 5-10 mm clearance), the pump is actually sucking itself onto the bottom of the tank. Hard to say, my X-ray vision abilities ran out many years ago.:lol:

[Chris32]

fixed that noise, its pretty simple to fix. I found out that the return line from the motor was blowing air around the pump, causing the noise. Was better with a full tank of fuel, but still not right.

I attached a peice of fuel hose to the outlet and placed it so the fuel coming back was pumped at right angles to the pickup and the air bubbles were not near the pick up. No more noise.:uh-huh:

[blind_elk]

That's great.

Question remains - where is the air coming from?

[Chris32]

I reckon its caused by the massive amount of extra volume that the pump is pumping. It would be pumping much more fuel back, and when its getting to the outlet pipe in the tank its blasting back in around the fuel tank , causing air to be pushed from the tank into the fuel around the pump, like when you squirt a hose into a bucket of water. By re-positioning the line coming back in, the fuel isn't pumping air around the pump., and no more noise