Fuel pump noise

[mt308]

Last year I had some issues with the filter being blocked with some swarf material from the tanks (they don't use this stuff any more I understand).

The car cut out a number of times when hot - once I cleared out the 100m filter it has not happened again (there was some metallic looking material in there).

However - when my tanks go below about half full I get a much higher pitched noise from the fuel pumps - why would the pitch change just due to less in the tanks?

I'm concerned this is due to more rubbish in the filter putting the system under strain again - I will clean it out when I service her next month.

Not sure if linked - but also when I stop the car after a longish run I get a lot of bubbling into the fuel surge tank for a couple of minutes. Is this normal too?

I am running standard Ultima factory set up high pressure and low pressure pump systems with a surge tank, on an LS7.

Just wondered if anyone else notices these noises changing? My concern is that it could be due to the pumps struggling due to restricted flow.

Thanks

Mark

[mt308]

MarkWebb said:

Increased noise usually caused by cavitation in pump. Bubbling in swirl pot may indicate hot fuel. I have given my theories many times. Some of us get it others don't. Personally going for complete fuel system simplification and redesign using modern electronics as used by all big power car manufacturers to combat these problems.

Thanks - and I remember you being very helpful when I had my issues last year.

I have since put insulation around the swirl pot and inner sides of the tanks, they are much cooler now (the swirl pot used to be hot to touch, it isn't any more). My previous issues of cutting out were cured completely by a combination of the insulation and the cleaning of the filter (probably mainly the latter), but I have recently started to notice high pitched noises from the pump now which I think were happening around the time of the cutting out issues I had. And definitely seem to be worse with a less than full tank.

It is operating fine now from a performance aspect, so I don't plan to re-design anything at present.

That swarf material is a pain!

Cheers
Mark

[mt308]

OK, so dismantled entire system, no sign of anything wrong. Replaced high pressure fuel pump as that I think is the one that was cutting out. Replacement Bosch unit.

Initial restart much quiter than old one. BUT after driving for half an hour or so and getting it really hot the horrible noise has returned. Could this noise - which is a high pitched buzz (and which with my old problem used to get worse until it cut out) actually be just due to the chassis and surrounding area getting hot and vibrations changing and not something to worry about?

I was waiting for it to cut out today in a bit of light traffic but it did get me home. I then left it running for 15 minutes stationary in the garage and turned air con on full for good measure. It didn't cut out.

Maybe I am paranoid now but the noise is most definitely way louder and higher pitched when the car is fully warmed up. This high pitched noise is very similar to before....

The swirl pot and tanks were not that hot even sitting there for 15 mins on after a good run. Before it was getting quite hot. Its just the noise.

All I have not replaced now is the low pressure pump. But I am told that is not such a high pitched sound.

I am assured that my standard factory set up is used on cars that are in Dubai where they are driven in 40C heat.

I am not currently filled with confidence when planning a trip to France with my wife where it could be a lot hotter than today and where I plan to do 250 miles or so in one run. She is rapidly building a dislike to the car!

Does anyone else notice any changes in noises when their cars get warm/hot?

Mark

[mt308]

Storer said:

Mark

Where is your fuel pressure regulator situated?
What is the pressure when the engine is cold and when hot?
What make is it and did it come from the Factory and roughly how old is it?

You can tell from the above that I am wondering about the regulator.


Paul

On the rear bulkhead up high. Factory supplied. They removed the gauge as they can leak I was told. Maybe I should put it back on and check pressures?

Car was new built by me only on the road for 2 years. 3,500 miles or so.

Its an Aeromotive.

Thanks
Mark

[mt308]

Storer said:

The easiest way to tell where the noise is coming from if it still makes it when ticking over is to use a stethoscope.

A simple metal rod with a piece of wood on the end for you ear. Place on each component.

Worth a try.


Paul

Thanks - will do that. Forecast for tomorrow is awful so might not get to it this weekend.

Mark

[mt308]

Storer said:

Mark

There were issues with some Aeromotive regulators that were faulty a while back.

They seem to have got over to this side of the pond!!!

The best way to tell unfortunately is replacement .


Paul

Paul

Thanks - would the noise be explained by this?

If they are faulty, if a knowen issue, I wonder if they will replace it even though out of warranty.

Mark

[mt308]

F.C. said:

If you are using 044 Bosch high pressure pump then the noise is almost certainly a restriction to the pump inlet.
These pumps don't like sucking and get noisier the harder they have to suck.
One thing to check that isn't obvious is the fuel pipe from swirl pot to pump inlet I have had these collapse internally with no outward signs (on a Noble) of degradation.

Interesting - now I am running out of ideas maybe just trying new pipes is worth a go. Though I have to say more likely to be the outlet as this is where there is a bend. But you say its the inlet only that would cause the noise?
Yes its a 044 Bosch.

I wonder if heat build up causes a degredation?

Just looking at the diagram now there are 2 flexible pipes from my swirl pot to the HP pump. One goes from the bottom of the swirl pot to the 100micron filter (which I have just cleaned - interestingly when I cleaned it I thought there was some very fine black plastic apparent, degraded pipe perhaps? but nothing that would cause any material restriction) then a pipe from the filter to the HP pump (which is brand new). The old HP pump I removed had nothing in the integral gauze filter at all, but did has a small piece of metal - similar to a piece of swarf - in the mechanism, my thoughts on this were if it was overheating it could be internal damage.

Very concerned for 2 reasons - 1. My engine cost me over £20,000 and could be damaged here, 2. I have no faith I am going to make it to the end of any journey greater than about 20 miles.

Perhaps replacing both those pipes is a sensible next step. Just to confirm - are we saying the system up to the swirl pot is probably not the issue, it is the feed from swirl pot to HP pump?

Mark

Edited by mt308 on Sunday 31st May 21:48

Edited by mt308 on Sunday 31st May 22:17

[mt308]

Storer said:

Try the metal rod to find the source of the noise.. Works on pipes and fittings too.



Paul

Will do - next weekend as I need a decent drive to get noise, but not too far in case I don't make it home.

This noise has been happening ever since the car was brand new - half way back from the factory the pump got much noisier but as the car was new and I didn't know what to expect I sort of ignored it. But it didn't actually cut out until about 2,000 miles on the clock.

Thanks

Mark

[mt308]

AndreasW said:

mt308 said:

This noise has been happening ever since the car was brand new - half way back from the factory the pump got much noisier

My car has also a Bosch 044 installed which is quite loud since it has been new.
The pump sits inside of a surge tank (http://www.performancebyie.com/ie-submerged-044-billet-surge-tank) which is installed horizontally.
Its intake position is below the lower dash ports of the fuel tanks - so that the fuel runs into the surge tank by gravity.
Once the fuel tanks are half empty, the pump starts to be noisy.
By googling you can find a lot about noisy Bosch 044 that behave exactly the same way.
Obviously the Bosch 044 requires a certain amount of pressure on the suction side.

Thanks. My surge tank is fed by a separate low pressure pump so I don't think the level in the tanks should make any difference to the pressure on the feed on the high pressure pump intake.

I used to think the noise increased as the tanks emptied but now I think it is actually just as the system has been running for a while - 25 mins or so seems to do it.

Mark

[mt308]

AndreasW said:

mt308 said:

I am not currently filled with confidence when planning a trip to France with my wife where it could be a lot hotter than today and where I plan to do 250 miles or so in one run. She is rapidly building a dislike to the car!

Does anyone else notice any changes in noises when their cars get warm/hot?

The noise of my pump does not change by temperature (my surge tank heats up barely).
During the cold-start phase (rich mixture) of the engine the pump remains silent, even if the tanks are half empty.
Once the engine has operating temperature the pump gets progressively louder.
I think it is not as noisy while driving but only at idle (maybe I'm wrong because of the loud driving noises).

This led me to believe that the pressure regulator (in my case, original GM) at idle almost must lead the entire fuel the pump delivers (my pump is not controlled and runs on full power) back into the tank - and the bottleneck is in the return line of the regulator (which can not be changed) what leads to cavitation inside the pump.

So far I had no problems and I traveled distances of around 500km length in one piece.

OK - still trying to work out what my issue is. Maybe someone can help explain how the system is designed (factory standard system with 2 tanks, low pressure pump, surge tank, high pressure pump (just renewed - Bosch 044)).

My pump also gets (VERY) loud when up to temperature, and sounds under quite severe strain - as discussed above many times it has actually cut out.

Can I check my understanding of the system is correct as follows:

1. Low pressure pump feed fuel, unfiltered, into the surge tank - bottom of the 3 side connectors (I have no filter pre-surge tank)
2. High pressure pump draws fuel from bottom of surge tank, through a line with an in-line 100 micron filter
3. High pressure pump delivers fuel, through a line with an in-line 10 micron filter to the fuel regulator, my pump runs full pelt the whole time, no speed controller
(1-3 above is statement of fact on my set up)
4. At the regulator, fuel is sent to the injector rails to maintain 60psi (or maybe 57psi) of pressure. The remaining fuel flows back into the return line into the swirl pot - middle of the 3 side connections.
5. (just edited!) The top of the 3 side connections on the surge tank flows back under gravity/pressure from the low pressure and high pressure feeds into the tanks. This has a 2mm or so restrictor fitted which creates a pressure inside the surge tank. But inherently this pressure surely makes the HP pump (and LP pump for that matter) push uphill against pressure as the fuel can only trickle back down the line to return to the tanks. So pressure inside the surge tank builds and builds, as LP and HP pumps both running at full pelt all the time and the only escape being through a 2mm hole back to the tanks, potentially explaining why at idle the noise seems to get worse (and also at idle where the system has cut out on me in the past).

Its 5 above that I don't understand. Why have a pump pushing fuel into a restricted line? Does this not put the pump under pressure? (an extreme would be to completely block the outlet to the HP pump so it can't pump at all). This is the observation AndreasW makes above.

When I turn off the engine I am getting at least 1-2 minutes of gurgling/bubbling inside the surge tank. What is this likely to be? (I am thinking either it is air from inside the system (cavitation) or there is a pressure imbalance (vacuum) being created).

Could a faulty regulator cause these symptoms?

Other than the surge tank itself, and the fuel lines, I am running out of things to change, other than perhaps changing this restrictor to a 3mm or 4mm restrictor? The factory assure me there are dozens of cars out there with exactly my set up (engine and fuel system) - so suggestions of throwing it all away and starting again is something I am holding off doing for now, if nothing else than due to costs and time.

I still am not sure the advantages of running huge volumes of fuel around the system when the car is not under load.

Should also note that when I just removed the top of the 3 mountings from the side of the surge tank to check the restrictor, as I undid it I got a hissing noise (pressure relief). Is that to be expected? No fuel at that level - no drips at all removing this top line.

HELP!!!

Thanks
Mark

Edited by mt308 on Monday 8th June 21:52

Edited by mt308 on Monday 8th June 21:56

[mt308]

Steve_D said:

Right let’s take things one at a time.
1. I would have the coarse filter in the line from LP pump to swirl. Reason HP pumps don’t like sucking so a restriction like the filter could cause cavitation. Which incidentally is where I think your problem lies.

2. HP pump should draw from the swirl with no restriction, should ideally be below the swirl and should have the largest bore practical.

3. This is as it should be.

4. This is as it should be.

5. Which return line has the restriction? If it is the line from regulator to swirl then that is wrong it should be in the line from the swirl back to the tank.
The reason is as you say to create a pressure in the swirl to help eliminate cavitation at the HP pump.
There are two fuel circuits in the system. The LP pump pushes fuel into the swirl pot but anything that does not get used would return to the tank if it were not for the restrictor. The LP pump is self-regulating to about 6 psi so there is actually no reason for the fuel to return to the tank. You do however want any air trapped or generated within the system to escape which it can do past the restrictor. Personally I think 2mm is too large
The second circuit is the HP starting at the swirl is drawn into the PH pump (assisted by the back pressure created by the restriction in the LP return) through the filter, regulator then either injectors or down the return line to the swirl. Don’t think of it returning to the tank just think of it going back round the HP circuit again.

6. If I’m reading this correctly then I believe this to be wrong. The HP return should go to the swirl. The LP should go from swirl to tank.

I suspect your gurgling is in fact air/vapour caused by cavitation and/or the drop in pressure causing the fuel to locally boil at the entry to the HP pump.


An experiment you could try would be to block off the return to the tank and see if it make a difference. As I said the only reason for a return is to let air/vapour escape but you can ignore that just for the duration of the test. I suspect also the 2mm restriction is not actually producing the required back pressure as it is too large.

Steve

ETA I have a couple of pdf files with diagrams of what I have just described which I could send you. I don't think you can attach them to a post although I have never tried.

Edited by Steve_D on Monday 8th June 22:16

Thanks Steve - I did edit my post as I had made a mistake. The restrictor is on the return line.

[mt308]

Storer said:

If your 100 micron filter is after your swirl pot then it will be worth checking the cleanliness of the filter AND the swirl pot. Possibly also the low pressure supply pipe to the pot and to the low pressure pump as there have been issues with the plastic tank filler getting into the fuel system.

I go along with everything else Steve has said.


Paul

Hi

Yes I agree there could be stuff in the swirl pot. Might be a silly question - but how do I check the cleanliness of the swirl pot? I have cleaned the filter - not that much stuff in it but there was a bit.

Thanks

Mark

[mt308]

Update following some work on the car.

I have replaced the fuel hoses from the swirl pot to my filter and from filter to HP pump from -6 to -8 bore (including welding on a new -8 fitting to the bottom of the swirl pot). -6 pipes remain elsewhere in the LP system and form the HP pump to the engine.

I have also fitted a Fuel on Demand unit to slow the HP pump down when not under load. This makes an amazing difference in the current draw of the Bosch pump. Where previously it ran at 10amps constantly whether at idle or during generally pretty brief moments of full accelaration, returning on low demand and at idle probably 80% of the fuel back into the system, the new system runs at around 2amps at idle and even when running constant low revs doesn't go much higher and hopefully now returns very little back into the system. So hot fuel should be mainly ending up in the engine and out the exhaust.

8 amps less demand sitting in traffic can't do any harm to the battery load either, especially in the heat with air con and cooling fans on full pelt for long periods (e.g. Silverstone I expect). Should also make the car at least a little quieter - the noise will now be a big V8 mainly!

Time will tell if this set up works. I will find out on run up to Silverstone next weekend in the convoy...

Mark

[mt308]

Fuel on demand unit from Professional Products. Pipework and fittings from Speedflow, local engineering firm did the welding on the swirl pot.

Mark

[mt308]

I have just been testing my fuel on demand unit. Drove it with the laptop connected.

As stated before the Bosch 044 pump draws 10 amps when running at full rate. With the FOD fitted at idle it is around 2 amps. Cruising along at 80ish in top gear this goes up to around 2.5 amps. Even under quite hard acceleration it doesn't get much about 3.5 or so.

The best I managed was foot to the floor in 4th at 6,000rpm (briefly!) when I managed to get the current up to 5.5 amps or so for maybe 2 seconds before backing off (this was on the road!) and then it settling back down to 2.5 or so.

Silverstone will be a good test to see if my cavitation issues are resolved...looking forward to seeing some of you there.

Mark