Central heating pump for diesel

[Doctor Drivel]

** snip overt idiotic senility **

Care in the community has clearly failed.

[Roger]

The message from "Doctor Drivel" contains these words:

You can say one thing about Dribble. However absurd his views are he will stick to them like shit to a shovel.

Most of us don't need to know anything at all about that particular engine to realise that the closest any output from the fuel pump can come to indicating road speed is to feed a rev counter. Some of us may even be able to tell our road speed from the reading on a rev counter but that requires in addition to a knowledge of final drive ratios the certainty that the clutch is not slipping. While the fiendishly clever Nipponese might be able to devise such a box of tricks they are also clever enough to understand you don't spend many times the cost of the standard solution to provide an inferior alternative.

[Dave Plowman (News)]

Don't need to - unlike you I understand the principles these things work on. Fuel pumps these days on most engines are designed to give a near constant pressure to the fuel rail. Which bears no relation to the road speed. And even in an old design where the pump supplied to demand the road speed had little bearing on this. Maximum demand might well have been climbing a steep hill at 20mph...

Perhaps one day you'd just admit when you're wrong, shit for brains. Fat chance.

[Doctor Drivel]

"Roger" wrote overt Rogerness in message news: [e-mail]...

** snip Rogerness **

It may be that Roger. I know was a round thing on the dash that didn't work, but now it does because he used Ultimate fuel, which is the prime point. Your Rogerness is getting to you Roger, you must see the prime point.

** snip babbling Rogerness **

[Dave Plowman (News)]

It's the complete lack of basic knowledge that shows all the time. If he can't quote a website or advert he's lost. And in the past claimed to have some form of engineering degree.

A child of 5 who's played with a Meccano set could tell you you won't get road speed off any fuel pump for an IC engine.

[Dave Plowman (News)]

Very technical description. Could be the cigarette lighter?

No, the prime point is that you wrote rubbish and didn't realise it. And as usual refuse to admit your crass stupidity.

Going on to your advert for Ultimate, perhaps you'd explain how a device which measures rotation against time could work/not work by the fuel going through a pump? Because either the pump works or it doesn't.

Older OBCs used a flow sensor in the fuel line to determine fuel consumption. This could possibly get blocked with crud. Dunno if this was ever used with diesels, though.

[Andy Dingley]

Never, AFAIK. Too many diesels (even years ago) recirculated fuel back to the tank. Obviously this makes fuel volume measuring awkward with a simple flow sensor in the pipe.

Injected petrol engines control fuel flow by varying the injector timing

- just when it's open. Diesels with mechanical injectors did it instead by opening a spill port. The injection pumps run at a constant volume no matter what the load, but the excess when running light is spilled into an overflow, rather than being sent to the injectors. Recirculating this spillage round the pump itself would soon churn the fuel into a froth and over-heat it, so instead it's sent back to the main tank. If you have a cold-climate diesel there's usually a small header tank (where the dewaxing heater is) and the spillage pipe only goes that far back.

[Dave]

Aye. So it would seem...

[Dave Plowman (News)]

Yes - I suspected this. And many petrol engines have done the same for many a year - even before injection became the norm, as it helps prevent fuel evaporation. My '69 Rover P6 did. However, it was possible to use a flow counter into the carbs. The SDI carb cars did this for the OBC. Later injection ones measure injection opening.

Yup - as I'd guessed, but I'm no expert on diesels. But it certainly gives the lie to dribbles idea that it drives the speedo. Or revcounter, come to that. They're usually driven off an AC output from the alternator.

[Matt]

I'm not Lord Hall

That's a bit magic that is. Does it just guess the gear ratio then or does it not have a gearbox? Maybe it's like the Prius and has a CVT Gearbox like what you said.

Now that bit I can believe.

Are you really, really sure he didn't squirt some diesel onto the speedo head?

:-)

If you didn't exist no amount of computers, no matter how badly programmed by Microsoft could ever come up with such utter Dribble.

[Mr X]

In article , Dave Plowman (News) writes

All "traditional" diesels with the classic mechanical injector pump will have a flow and return fuel line.

I seem to remember having this on my 2 Nova's

I suspect it makes the carb design better/cheaper as a float and valve is not required, and the design of the fuel pump as well as the fuel pump is not required to stop pumping when the carb float shuts its valve.

[Andy Dingley]

My Dad's 1932 MG has a huge rev counter and no speedo. The rev counter is calibrated as a speedo for 3rd and 4th gear.

[Dave Plowman (News)]

All the ones I've seen still had a float and valve.

Older single pipe designs will have had some form of pressure limiting device in the pump. SU electric simply stopped pumping. ;-)

[Roger]

The message from "Dave Plowman (News)" contains these words:

If I understood what the service engineer said my neighbours tractor (a Zetor) which only has a rev counter (and a hour meter rather than an odometer) has a pulse counter somewhere on the fuel line to drive the rev counter.

[Andy Dingley]

I doubt this. (Somewhere) I have a pile of fuel line pressure sensors for diesels, all broken. They weren't cheap, and they're just about the least reliable sensor I've ever used. Even for a job with a decent budget we could buy these things easily enough (several makers) but none were reliable in service, let alone long-term.

If you want to measure revs, just count the shaft turning, that's dead easy.

[Grunff]

ROFL!!

So your 'speed' is actually your fuel consumption. That means you go faster uphill than you do downhill.

[Matt]

Quite common. Something similar is commonly used during diesel servicing for setting the pump timing. You can get a sensor that clips round the injector piping and this then provides a trigger signal for conventional timing lights.

[Matt]

In the land of Zog anything is possible.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Dave Plowman (News)" saying something like:

Drivel is thinking about the vacuum pump being taken off the back of the alternator on some engines, and randomly associating likely automotive-sounding words with the concept of something driving something else. That, and listening open-mouthed to his 'mate' blathering on about something he knows only slightly more about than Dr Drivel.

Example:

I drive a ShiteOldJapCar

I drive a nail into Drivel's head.

You see the difference? Both make perfect sense, but the first one is relatively environmentally friendly.

[Andy Hall]

I'd have said that the second one was......