Fuel Consumption Issue

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Stuarted
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Fuel Consumption Issue

Post by Stuarted »

Both the BX 19 diesel estates I have owned previously gave consistently good fuel consumption (invariably 50 to 53 mpg) whether driven fast or slow, in town or on motorways.

This is measured in the most accurate way I know: noting mileage at each fill-up and then (1) dividing latest incremental mileage by latest fuel load to give current fuel consumption, and also (2) dividing total cumulative mileage by total cumulative fuel to give overall average fuel consumption.

My "new" one, so far, seems to do just 40 mpg even when driven really steadily and carefully. The previous owner did not appear to get particularly good fuel consumption from it either.

I have checked obvious things like seized brakes and tyres pressures but all seem to be OK. Can anyone suggest anything else which might adversely affect fuel consumption? Perhaps poor compression? (Car has done 190,000+ miles, but my previous ones had done 250,000 and 180,000 respectively ...)

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citsncycles
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Re: Fuel Consumption Issue

Post by citsncycles »

Timex isn't as economic as it should be, although certainly not as bad as yours. I can get about 48mpg as my version of steady driving, dropping to about 40mpg when I push it. I know that one issue with mine is I still haven't got the pump timing right, mostly down to my own inexperience with the job. This is also a possible reason for the smoke on startup on mine, as the glow plugs are fairly new and the smoke is more due to unburned fuel than burning engine oil.

What age is yours - I know that some of the pumps are timed differently depending on their age, and Timex looked like it had been timed up as if it was a later pump fitted.
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barry badger
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Re: Fuel Consumption Issue

Post by barry badger »

My txd is poor on fuel but pulls well and doesn't emit any excess black smoke, I've replaced the injectors and fiddled with the pump timing but no difference, It has a different sound to the engine than is usual for an xud and emits a little blue smoke until it's warm. My next step when i've got time is to check the cambelt timing, medway citroen changed the cambelt 2 months prior to me buying it. I'm hoping it's a tooth out on the camshaft.
Another possible cause of poor fuel consumption could be a partially blocked exhaust.
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MULLEY
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Re: Fuel Consumption Issue

Post by MULLEY »

Have you tried the obvious things 1st, fuel filter & air filter, they are the cheapest things to do which can affect fuel economy. If that doesn't do anything & its not the pump timing out, then it might be an injector or 2 that aren't working as efficiently as they can, try some injector cleaner to see if that doesn anything.
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kiwi
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Re: Fuel Consumption Issue

Post by kiwi »

This thread pricked my interest and well timed topic.

Last fill up of my TXD the fuel consumption a bit on the heavy side, actually the lowest its been since I got it. May be panicing about nothing just when you keep consistant logs and driving habits this kind blip noticeable.

Worth making notes though.
1991 BX19 TZS 04/01/91 (Deceased)
1990 BX19 TRS 27/10/89 (Reborn)
1992 BX19 TXD (Ex UK - K 744 SDF) 15/06/92
1990 BX19 TZS Auto 06/11/1989
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Tim Leech
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Re: Fuel Consumption Issue

Post by Tim Leech »

When I bought my 19TZD (RIP the red shed) a couple of years ago it was rather sluggish, some injector cleaner, new airfiler and a (Italian tune up) made it run much better!
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mat_fenwick
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Re: Fuel Consumption Issue

Post by mat_fenwick »

A clogged fuel filter will likely flow sufficient fuel up to a point, then run into trouble. Whilst it can't do any harm to change the filters etc, we're looking at a 20% + difference in consumption here which is more than I'd expect to be just down to neglect. As it is new to you, is it based on more than just one tankful? Although the PO reporting poor figures would tend to rule out a dodgy fill.

Poor compression is likely to give problems starting; also pressure in the crankcase/breather system. Any pressure when you pop the oil filler cap off? Does it seem down on performance compared with the other two? I've heard people suggest that there is a difference in economy (and performance) between Bosch and Lucas pump equpped vehicles, but can't say myself. I'd doubt it would be that significant though!
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Brian
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Re: Fuel Consumption Issue

Post by Brian »

Just some sugestions:

check the mileometer against a measured distance.

Are you running on standard tyres?.

I have also noticed that Lucas pumps tend to be less fuel efficient compared to Bosch ones.

Good Luck and if you do manage to find the cause, let us know.
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kiwi
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Re: Fuel Consumption Issue

Post by kiwi »

Brian wrote: check the mileometer against a measured distance.
That!

If you have access to even one these cheapo GPS you will be able to gauge how accurate your speedometer actually is, reality is if the speed is out so will be the distance.

Not pushing a brand here (yes I am) the Garmin range of car GPS probably the best on the market for distance measuring (providing you switch them on every trip). Use one of them to measure a fuel run between fills. You may be surprised with the results.

Of course another common mistake is the correction of adjusting Miles per litre to miles per gallon. Seems that mistakes often made in that conversion.
1991 BX19 TZS 04/01/91 (Deceased)
1990 BX19 TRS 27/10/89 (Reborn)
1992 BX19 TXD (Ex UK - K 744 SDF) 15/06/92
1990 BX19 TZS Auto 06/11/1989
1992 BX TZD Turbo Estate (Ex UK) 1/07/91

Stuarted
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Re: Fuel Consumption Issue

Post by Stuarted »

Thanks - all good, sensible and logical suggestions.

However (as I was at at pains to try to make clear in my OP) this is driving familiar routes in a similar manner and using exactly the same measurement and conversion process as ever. The consumption was consistent before (in both previous cars) and is consistent (and and consistently worse) now, by - as mat_fenwick observed - a factor of some 20%. The mileometer of my "new" car, if anything, is showing slightly greater distances than I actually cover, so is, if anything, slightly flattering my fuel consumption.

Investigations (as they say) continue and further suggestions / comments are welcome.

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MULLEY
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Re: Fuel Consumption Issue

Post by MULLEY »

I'm hedging my bets on injectors, if they aren't working correctly they'll be inefficient & could use quite a lot of extra fuel. Does the car have any other symptons such as extra smoke when booting it or just idling, does it idle steadily or does it hunt a bit?
2002 C5 2.0 HDI Estate - Jasmine - Now SORN
2011 Mini Cooper D Clubman - SOLD
2016 Mercedes A180D Sport - Auto refinement
1992 TZD Turbo - Bluebell - My daily
1991 Gti 16V - Blaze - crash damaged, will get repaired.
1990 Gti 8Valve SOLD - looks like it's been scrapped
2002 Mini Cooper S - SOLD - i miss this car
1992 TXD - Scrapped in March 2014
1988 CX 25 GTI Turbo2 - SORN
1996 - AX Memphis 1.5D - Dream - SORN

I'm not just a username, i'm also called Matthew.

Stuarted
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Re: Fuel Consumption Issue

Post by Stuarted »

Not noticed it "hunting" and I will check for smoke.

What's the cure for injector probs please? Some form of injector cleaner in the fuel?

Stuarted
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Re: Fuel Consumption Issue

Post by Stuarted »

I love diesel cars but I am ignorant about diesel engines, having grown up only with petrol engines and having spent lots of time taking these apart and fiddling with carburettors, distributors etc.

So: regarding diesel pumps - never had a close look at mine. It's just that complicated lump on the front of the engine with a throttle cable and loads of high-pressure pipes running from it. Is it easy to see if it is a Bosch or a Lucas one, please? Are they easy to fit / remove / change? Would it be worth removing and keeping the pump off my old dead car? How is its timing set? How can this be checked?

And, talking of timing - is there any simple way of checking the timing of the camshafts, without dismantling the engine? This car has had its cam belt changed a few years ago, but frankly I would have thought that if the camshaft timing was wrong (or the diesel pump timing, come to that) then the engine would run so badly that this would be immediately obvious. My car seems to run fine. OK not a fire-breathing, road burning beast but then, no 1.9 NA diesel BX ever was. It runs smoothly and sweetly and ticks over calmly. None of my 19TD BXs did acceleration. I wouldn't expect them to. These cars don't do performance (I've got an MX-5 sports car for that!) - they do economy. Or they should - my new one doesn't, or not very well.

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mat_fenwick
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Re: Fuel Consumption Issue

Post by mat_fenwick »

Fuel additives can clean injectors to some extent (I've noticed an improvement in performance but not in economy) but for a proper job you'd wan to take them off and get them professionally cleaned. There are other things which can be amiss with diesel injectors - not just that they need a clean e.g opening pressures, leakage, etc. I'd expect injector problems to show some smoke - i.e. if the fuel is not atomising properly then you'd tend to get unburnt diesel passing through in the form of whitish smoke.

If you can check the pump for maker's markings that would be the sure fire way to tell which you have (it is what you describe!) If they aren't visible, the stop solenoid (single wire leading to it) on the Bosch pump is very difficult to get a spanner onto it as it's close to another part of the body. On the Lucas pump it's more in the middle.

Pump, pipes and injectors need to go together - not just a case of changing the pump. It's timed by loosening its securing bolts and rotating it in slotted holes - either by ear or with a DTI into a timing hole. Cam timing can only be a tooth out (or multiples of!) But if a tooth out you would notice, and if more than one tooth you'd likely have valve to piston contact.

Does the filler cap lock OK? Wondering if you have a thief...
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1993 1.9 TZD Turbo Estate
1996 3.9 V8 Discovery
1993 VW LT35 campervan
1985 Hyundai Stellar V8
2016 Hyundai iLoad

gary0006
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Re: Fuel Consumption Issue

Post by gary0006 »

I get 47mpg with mine



Stuarted wrote:Both the BX 19 diesel estates I have owned previously gave consistently good fuel consumption (invariably 50 to 53 mpg) whether driven fast or slow, in town or on motorways.

This is measured in the most accurate way I know: noting mileage at each fill-up and then (1) dividing latest incremental mileage by latest fuel load to give current fuel consumption, and also (2) dividing total cumulative mileage by total cumulative fuel to give overall average fuel consumption.

My "new" one, so far, seems to do just 40 mpg even when driven really steadily and carefully. The previous owner did not appear to get particularly good fuel consumption from it either.

I have checked obvious things like seized brakes and tyres pressures but all seem to be OK. Can anyone suggest anything else which might adversely affect fuel consumption? Perhaps poor compression? (Car has done 190,000+ miles, but my previous ones had done 250,000 and 180,000 respectively ...)