Fuel Pump Buzz

[Guest mcramsay]

Noticed on the last few trips out in the marlin that after an extended period of driving I can hear the injection pump buzzing really loudly. Seems to stop when I Rev the engine and then returns on idle. No issues on the engine that would lead me to suspect that the fuel pump is giving up.

 

Will get another pump just incase but has any one had a pump fail like this? There are filters pre and post both lp and hp pumps, the hp pump is mounted vertically in the engine bay with a gravity feed from the swirl pot.

 

It sounds like the pump is running dry... but if it was the engine would splutter and miss which it doesn't .

[fry61]

The pump on Florin makes more noise when re-starting after a run. Typically as per to-days run -- 30 miles driven -- stopped for lunch -- more noise from pump on restart -- quietens after a few miles. Have reasoned its fuel vaporising a little in the pump on warm days . It's a slight worry -- is there a solution?

[Longboarder]

I wouldn't ignore it but my experience has been coloured by several strandings caused by pump failures, one at Llandow (LP), one at Newark (HP), one at Barkstone (LP filter) to name but a few. I am of an age where I can't remember what I had for breakfast but each and every splutter, coast to a halt, not fuel supply again moment, call to the RAC is seared indelibly on my brain cell.

Most pumps have a pathetic suck and a powerful blow. Pre-LP-Filter blockage or partial blockage has been the common denominator. (To the extent that I carry spare £1 ebay cheapo LP paper filters in the Hood. And spare LP and HP pumps) The bullet type Facet filter has a very small area and easily gets restricted with only small amounts of crud such as from a new build tank or debris from dirty petrol from the forecourt. The paper type can also suffer the same. This leads to reduced/no flow to the swirl pot and the HP pump running dry or semi dry, getting noisy and failing. But even the bigger inline paper filters can clog, especially after you have given the car and fuel tank a good shake up on a track day!

I would not put too many filters in either. A single large cheap paper type inline filter pre - LP pump. No post LP pump filter. No pre - HP pump filter. Micro filter after the HP pump. And change the pre LP pump filter at least annually.

Another thought. Your swirlpot. Does the return line from the fuel rail return to the pot. It should.

 

Nigel

Edited April 3, 2017 by Longboarder

[Guest mcramsay]

Now you mention it I have heard the lp pump make some funny noises as well, I am using one of the units with the built in filter screen rather than bullet filter, might be worth whipping the filter out. Also when the fuel pump is buzzing it might be worth listening if I can hear fuel returning to the tank, that would indicate the swirlpot is full.

 

Swirlpot returns to the tank from the top connection. And has a return from the fuel rail aswell,

[Longboarder]

You have to have a filter before the LP pump. Fuel getting through this will then be clean enough to not damage it or the HP pump. (Any filters between the two pumps are redundant and reduce flow.) Usual big high pressure injection micro filter after the HP pump. I would advise changing the prefilter straight away on the assumption that there was some crud in the fuel tank from the build and this has been flushed through in the first 100 miles and is clogging. These are what I use. Cheap enough to change every 6 months.

 

Nigel

ps I have 8mm pipes and cut off the 6mm section from the filter.

Edited April 3, 2017 by Longboarder

[Guest mcramsay]

I had some time today so I had a look at the LP fuel pump, I'm using the golf flow pump which has a large 2" diameter strainer element located in the lowe inlet side of the pump unit, so you can undo the retaining cap on the bottom of the pump and withdraw the element, low and behold there is not much clearance between the pump inlet pipe and strainer, the whole inlet pipe and filter was cruder up with rubbish from the fuel tank from the build.

 

It doesn't look like anything has got through to the injection pump but I think the noise I was hearing was it running dry as the lp pump couldn't keep the swirlpot filled up on longer drives,

 

I m going to take a look at the injection pump but I suspect it will have some damage! And most likely worth changing.

[Guest lotusPaul]

Longboarder i beg to differ. I run a filter before my hp pump in accordance with its mounting instructions. Providing its big enougth it will not any restriction in flow to the pump. I also run another pre injetion rail.

[tractor]

i will only be putting a filter before fuel rail cos my fuel system is really simples high pressure pump and swirl pot in tank job done

[Dave R]

i will only be putting a filter before fuel rail cos my fuel system is really simples high pressure pump and swirl pot in tank job done

mine is the same.... bmw hp pump, stripped of all the bmw stuff, and in the tank... no issues so far. filter is mounted in the boot

[Guest mcramsay]

I am interested in sticking a pump in that tank and getting rid of the external swirlpot, the only things I can't work out is how do you actually mount the pump in the tank? And do you need to baffle the tank to get round the swirlpot issue?

[Mrbarry]

Why would you get rid of the swirl pot? That's rather a down grade. The idea of them is to make the fuel deep and narrow so that it doesn't slosh around in corners and cavitation the pump. The head of fuel in the pot also acts as a buffer whilst cornering hard and the low pressure pump is dry.

[tractor]

thats how mine is fitted had to have a raised collar made because even though i cut the pump dow my fuel tank is just to shallow

Edited April 11, 2017 by tractor

[tractor]

[tractor]

if you do go down this route make sure you cut hole in tank dead centre cos if you look at my picture you can just see my baffle plate in the tank assuming you have the same tank as me the baffle plate is mounted to one side

[Guest mcramsay]

i don't want to get rid of the swirlpot all together, just the need for an external one. Because it takes up room in the engine bay, looks a bit rubbish, needs double the fuel lines and needs to pumps, I would rather have a tank mounted pump with internal swirlpot and one feed and return line.