Filter filter changed, fuel pump noise

FlaatusGoat

Looking for some ideas on this one. NV200 Diesel Van. Changed the fuel filter the other day, pretty easy/uneventful. I even drew a happy face on the bottom of the new fuel filter. It's the cylindrical kind which means it's especially suited for that.

Did a 30 mile round trip today, and mid journey I suddenly noticed a whirring/whining background sound that I hadn't really heard before. Gut instinct, fuel pump not happy. Oh dear.

Have I done something schoolboy wrong when fitting it. Loose lines? I'll crawl under the said van tomorrow and see if I can definitively locate the source of the mystery whining sound to the fuel pump. Really would prefer not to need a new fuel pump. Sadly, I don't have the old fuel filter but they were like-for-like identical. The new one is a Mahle.

Confused.

Goudy

Did you connect the pipe work back in the correct order?
There is usually a feed from the tank, an outlet to the HP pump and a spill off return from the injectors (via a valve on the HP pump).

Are the pipes and connectors in good condition, notice any cracking of the pipes?
If one of these is pulling in a little air it'll vibrate when running (your whirring/whining sound). You can sometimes find the problem by gripping and wiggling the pipes.

Did you pre fill the filter with fuel and prime the system after fitting it?

A diesel's fuel system has to be air tight and modern diesels tend to loop the injector spill off back to the filter as mentioned above.

Some do this all the time and some do it just it to warn up.
A valve on the HP pump sends the injector spill off back to the filter when the engine is warming up, this recirculating the diesel heats the fuel up quicker and helps cold running.
Once warm the valve sends it back to the tank, only then can it vent.

This means if air gets in, it has trouble bleeding itself as the air just goes around the filter, pump, injectors and back to the filter, then starts the same trip again as it can't self bleed.

If a little air gets in you usually notice a stuttering on acceleration and it'll more likely stumble and stutter on idle as the air bubbles hits the injectors. If it loops back to the tank when warm, it'll likely clear after a good long, hot run.

Lots of air can air lock the rail and it'll not start/run.

Some diesels just don't like certain filters or filters have been know to be faulty.
My old X Type diesel just didn't like anything other than OEM (Delphi) or Bosch, anything else and it ran like a bag of spanners.

FlaatusGoat

Goudy said:

Did you connect the pipe work back in the correct order?
There is usually a feed from the tank, an outlet to the HP pump and a spill off return from the injectors (via a valve on the HP pump).

Are the pipes and connectors in good condition, notice any cracking of the pipes?
If one of these is pulling in a little air it'll vibrate when running (your whirring/whining sound). You can sometimes find the problem by gripping and wiggling the pipes.

Did you pre fill the filter with fuel and prime the system after fitting it?

A diesel's fuel system has to be air tight and modern diesels tend to loop the injector spill off back to the filter as mentioned above.

Some do this all the time and some do it just it to warn up.
A valve on the HP pump sends the injector spill off back to the filter when the engine is warming up, this recirculating the diesel heats the fuel up quicker and helps cold running.
Once warm the valve sends it back to the tank, only then can it vent.

This means if air gets in, it has trouble bleeding itself as the air just goes around the filter, pump, injectors and back to the filter, then starts the same trip again as it can't self bleed.

If a little air gets in you usually notice a stuttering on acceleration and it'll more likely stumble and stutter on idle as the air bubbles hits the injectors. If it loops back to the tank when warm, it'll likely clear after a good long, hot run.

Lots of air can air lock the rail and it'll not start/run.

Some diesels just don't like certain filters or filters have been know to be faulty.
My old X Type diesel just didn't like anything other than OEM (Delphi) or Bosch, anything else and it ran like a bag of spanners.

Thanks for taking the trouble and sharing your experience. No I didn't pre-fill the filter, just primed it. I've been back under the van and reconnected the hoses (4 in total) and re-squeezed the priming bulb. The hoses seemed OK but the angles are pretty tight. It's also not clear what hose goes into what pipe on the filter, though I've put them back exactly as they were previously. I'm hoping it's as simple as like you say just a bit of air getting in the system. I was told 2- 3years back that this engine can be very finicky when it comes to fuel filters. Pity I threw away the old filter, unfortunately. There's two arrows engraved on the top of the filter, I'm presuming this is the flow direction?

Goudy

Yes, the arrows tell you which way the fuel should flow.

From my time with diesels, I remember there usually being three ports on a diesel fuel filter. (two when I started with diesels)
In from the tank.
Out to the HP pump
Spill off return. 

I think the fourth is from a thermostatic device which puts warm fuel back into the filter to help in freezing conditions when diesel is like jelly.

This engine is shared with Renault and there are some posts relating to similar problems on Renault forums.
Most noise problems after changing the fuel filters tend to be pipes vibrating due to small air leaks.

I'm a bit out of date with diesels these days but there was a time it was common they fitted a clear fuel line to the last part of the fuel line up to the pump, just as it entered the HP pump.

This was so you could see any air bubbles in the fuel system, might be worth checking if it has and if you can see bubbles in there when it's running.

venomx

Interesting to read this.
Had a fuel filter replaced on my Mercedes with a Mahle one, and after a couple of days it is making a very odd noise.
Done some reading and it is common with these Mahle filters as there is a fuel pressure regulator inside it, the solution for most people is to replace it with a different manufacturer, I will be replacing the Mahle one with a genuine Mercedes part and hope for the best.

FlaatusGoat

Interesting interesting interesting...

I went under the van but with the stethoscope. That noise I'm hearing is most apparent on the exiting hose up to the engine and not so much on the one leading into the filter from the tank. I tried wiggling the connections on the filter and it made no discernable difference to the noise. So I'm less inclined to think it's an air leak and more likely to be the flow rate or regulation in the filter body itself. Interesting.....

So, time to buy another fuel filter and redo the comparison! Or, just live with the noise. Although I'm not sure the long term implications of that.

venomx

Replaced my fuel filter with a genuine Mercedes and seems fine now, howling gone, the noise was quite worrying.

I've heard reports of Mann, Mahle, Bosch, Febi, Cheap aftermarket and Genuine parts causing this noise and some people get unfortunate and get a bad unit.

sheslookinhot

venomx said:

Replaced my fuel filter with a genuine Mercedes and seems fine now, howling gone, the noise was quite worrying.

I've heard reports of Mann, Mahle, Bosch, Febi, Cheap aftermarket and Genuine parts causing this noise and some people get unfortunate and get a bad unit.

Mercedes do not make fuel filters. Any one of those manufacturers could be a “genuine” Mercedes filter.

venomx

sheslookinhot said:

venomx said:

Replaced my fuel filter with a genuine Mercedes and seems fine now, howling gone, the noise was quite worrying.

I've heard reports of Mann, Mahle, Bosch, Febi, Cheap aftermarket and Genuine parts causing this noise and some people get unfortunate and get a bad unit.

Mercedes do not make fuel filters. Any one of those manufacturers could be a “genuine” Mercedes filter.

Yes I know how it works.
The fuel filter from  Mercedes says " Knecht " on it ( along with Mercedes' logos ), which is related to the manufacturer " Mahle "

However, the Knecht division of the company Mahle only provide fuel filters to Mercedes, and not to the aftermarket.

What I was trying to highlight above is that any filter, regardless of manufacturer can cause the noise OP is mentioning

FlaatusGoat

Well well well.

Took the Mahle fuel filter out. Replaced with UFI part. Noise is GONE.

Can't be any more definitive than that. Whew. I was worried I'd have to put up with that noise forever...

Goudy

Glad it's sorted.
It's one of the oddities of diesels, some just don't like certain fuel filters no matter if they are listed as fitting.

It's a good idea to stick on what came off if it was running right in the first place.