Petrol filter.

[Dave Plowman (News)]

I've asked on uk.rec.cars.maintenance without much success so fall back to the experts.;-)

I've got a problem on the old Rover with the one way valve in the petrol pump failing. It's a fuel injected car so has a high pressure pump mounted underneath and close to the tank. There is a filter after the pump and a gauze one inside the tank which I'm told often fails by falling off. ;-) So what I need is a 1/2" fitting in line filter to go in the rubber hose between the tank and pump - there's plenty of room for near any size and shape within the transmission tunnel behind the pump.

I can get one from a specialist racing shop no problem - apart from the cost of anything up to 100 quid, whereas the normal disposable inline 3/8" type for the high pressure side only cost a few pounds. So can anyone think of a suitable lower cost one? It doesn't have to be a fine particle filter - the original only being a gauze type. And of course suitable for low pressure only. Perhaps something for a tractor? ;-)

[zikkimalambo]

What about using one of those disposable inline filters they use on the high pressure side, together with something to make it fit the

1/2" tubing? Or am I missing somethng? Alternatively, I wonder if the filters they fit on heating oil supplys would be suitable, or are they just water traps?

[Dave Plowman (News)]

I'm concerned it may restrict the flow since that is only gravity to the pump. The feed is 1/2" but with the more usual 3/8" output. And you

*really* don't want constant cavitation with a high pressure petrol pump.

Dunno - that's why I'm asking.

[Julian]

I'd question the wisdom of fitting a filter in the location you suggest. At the most you don't want any more than a strainer because positive displacement roller cell (is this correct?) pumps don't like to suck, and given the low vapour pressure of modern fuel it will cavitate and make noise.

But, many manufacturers don't even bother with even a strainer between tank and pump, so why fit one? I suspect you suspect that there's crap in the tank? IMHO you should remove the tank and clean it out and forget about fitting strainers.

Julian

[Dave Plowman (News)]

Indeed - hence my mention of a low pressure one.

I think you'll find all tanks have a gauze filter internally. And I've read reports that most pump failures are due to dirt entering them. My tank did have a gauze filter but it's broken off - hence the desire to replace it with something similar externally. Specialist ones specifically for this are available but expensive.

[Julian]

I don't think you understand the problem. The question is one of pressure drop or delta P. It has nothing to do with the mechanical strength of the filter - ie 'a low pressure one.' Any filter (unless it's the size of a dustbin for your application) will cause too much restriction or pressure drop. You can get away with a gauze or strainer but that's your lot.

No, (for instance) Audi deleted the tank strainer 1/2 way through one model production - car equipped with K-jet and L-jet. No problems result whatsoever.

And I've

Odd reports! Most expire through normal wear and tear. They slowly become noisy and pump current consumption increases.

My

Do as you wish, but you're barking up the wrong tree.

Julian.

[Dave Plowman (News)]

Hence the need for a low pressure one. Carb cars run at a pressure of only a few PSI so must have a non restrictive filter - compared to injection types.

Did I say it did?

Which is a filter.

Fine if that's your experience.

On mine the one way valve has failed. Likely caused by dirt, I'm told. And it so happens to have coincided with the internal filter braking off. So I'm not keen on the same happening to the expensive replacement I have waiting to fit.

I don't think I am.

[Julian]

As a rule (if fitted, and not just a gauze on the carb inlet or fuel pum) they'll be a small paper affair and fitted after a pump. Totally unsuited for a 'suck' through application for reasons I gave earlier on. Please try it though - I'll be interested in your follow up report!

It's what you _didn't_ say. Low pressure or high pressure - neither give an indication of pressure differential versus flow or the level of filtration.

Don't be so bloody argumentative, do drew a distinction between gauze and filter yourself in your opening post. Do you want a constructive dialogue or the normal f****it style newsgroup argument that you seem to enjoy with Doctor D?

Have you determined that this is the case? - You only seem to suspect this in your opening comments. What are the facts?

Julian.

[fred]

In article , Dave Plowman (News) writes

Totally agree with your logic, no knowing what crud is in an old tank or may fall in later.

Would a Y-strainer suit you? I thought of the CH ones that BES do but who knows if the sealing O-ring would be fuel friendly. Here's one that is fuel rated and only a fiver but it's 1" BSP, second item down:

some kind of fuel hose adaptor could be found or fabricated.

[Dave Plowman (News)]

They're also used with a much smaller bore pipe. So not suitable anyway.

I'd suggest you look at the sites which sell such filters for racing purposes. They are described as low pressure types. So I'm not going to argue with them.

There are mesh filters which seem to be the norm for this sort of job. Not gauze. You think a filter is not necessary and I think you're talking rubbish. It may not be needed on a new car or tank but this is neither.

I've given you the facts. And that I'm not willing to risk an expensive new pump without a filter.

[Dave Plowman (News)]

Thanks - that's some more choices. But there *must* be something similar somewhere in 1/2".

[Julian]

About £50-70? With the time, cost and effort involved with your proposals It's not worth the worry IMHO.

Here was what you said in post 1 on the subject:

There is a filter after

You have been _told_ it falls off - that's fair enough, but you haven't actually confirmed that's the case - have you seen it for yourself? I suggest that you have a look, that's got to be a better bet than all this buggering around prolly for nowt. Then clean the tank out and fit the new pump -job done. I don't believe in introducing an extra problem to overcome a (perceived) one.

Julian.

[Dave Plowman (News)]

180 quid.

There is something inside the tank rattling around and the most likely thing according to the club is the filter. Add that to the one way valve not working and if it quacks like a duck...

Removing the tank for cleaning is a far bigger job than fitting an external filter of the type I want. Also with an old tank how can you be sure you've removed every last particle that might be small enough to cause problems? I also tend to believe if a filter was fitted in the first place there's probably a reason.

[zikkimalambo]

There are one or two suggestions on here for filters to go between tanks and outboards which might throw up something

maybe you should try a classic motorcycle dealer, most of them were gravity fed with carbs, so any inline filters they have ought to be appropriate (if they are big enough!)

[Dave Plowman (News)]

That's the snag. The engine the pump is feeding is 3.5 litres so the gravity feed to the pump needs to be large enough to easily supply the required amount of petrol at maximum engine output. Motorbike filters - or rather the common ones - are too small.

[Richard]

Dave

Bearing in mind the popular use for a 3.5 Rover V8 (without having read the whole thread so apologies if this has been suggested earlier), have you asked alt.fan.landrover? Lots of experience there.

Richard

[Julian]

It needs to be large enough all the time, from tickover thru full power. The pump produces 100% output 24/7 - excess is returned to the tank via a pressure relief valve.

Julian.

[Dave Plowman (News)]

The pressure regulator controls the line pressure to the injectors. To counteract the effect of the manifold vacuum on them. There ain't no 'pressure relief' valve.

[Julian]

Your too far down stream. Before you even get there you need 'system' pressure, and this is controlled by a relief valve. How do you think pressure is controlled - perhaps via a variable speed pump perhaps! Tell me what system you have and I'll point you to a schematic, TBO I'm surprised at your lack of basic knowledge here.

Julian.

[Dave Plowman (News)]

If you'd actually been following the thread rather than just trying to show how clever you are you'd know what the car is and therefore the fuel injection system. The pressure to the injectors is strangely enough controlled by the fuel pressure regulator.