poor fuel economy BXTRS

kevlights · Post by **kevlights** » Sat Feb 14, 2009 7:46 am

my BX TRS 1986 5speed manual webber carb auto choke,lego dash model, 113,000 miles is getting poor gas milage,around town the vehicle farts about and misses and hesitates; ive replaced the fuel pump and spark plugs and high tension leads ; the plugs are black and sooty when inspected, your thoughts please and can someone tell me what i should expect to get on a trip around town from a tank and on a open road trip ; thanks Kev

ellevie · Post by **ellevie** » Sat Feb 14, 2009 8:53 am

Look at the quote below especially the stuff about the spade connectors.

ellevie wrote:I once had a very strange heat related ignition problem which took me years to isolate. Sometimes after shopping for about half an hour the car would refuse to start no matter how long I turned the engine over even with the pedal pressed to the floor as recommended by Citroen for warm starting. The strange thing is if I opened the bonnet and sat in the car for about 3 minutes then it would start on the button, every time. I eventually traced the problem to poor connectivity in the small connector on the distributor which carries the signal from the magnetic sensor to the amplifier. I measured a high resistance of about 10 Ohms on this short cable, so I bypassed it with a pair of wires.

At one time or another I have solved ignition problems by cleaning and reseating the various low voltage connectors in the ignition circuit. The spade connectors on the coil seem to be especially troublesome. I also once traced a missing spark problem to poor connectivity on the big connector to the amplifier which I cured by spraying the contacts with WD40 and reseating a few times. I have also more than once traced a rough idling pattern and cutting out to poor low voltage ignition connectivity. Somebody on the BX forum also recently traced lack of power problems to a poor spade connection on the coil.

So the moral is, before you go throwing money at the problem, just clean and reseat all the connectors shown on the illustration below. Also, if you have a resistance meter, check for good continuity in the signal path from the distributor to the amplifier.

BX Bandit · Post by **BX Bandit** » Sat Feb 14, 2009 9:32 am

Black and sooty plugs suggest a rich mixture. Do you ever take it on a long run? If so, clean the plugs up before you leave and examine them when you get back. If they are black and sooty again then you're running rich. either mixture or stuck choke!
Aim for a 'mustardy' colour on the spark plugs for correct mixture.

kevlights · Post by **kevlights** » Sun Feb 15, 2009 5:14 pm

ellevie

thanks for your very informative reply;i never thought it could be the distributor; will follow your recommendations as so as i get back from work;ohh bugger its just started raining again so will have to wait for "fix the car again weather" thanks regards Kev

kevlights · Post by **kevlights** » Sun Feb 15, 2009 11:41 pm

BX Bandit thanks your your input,probably right ,iwill get the carb checked out with fuel at $1.66 per litre for 95 octane unleaded; ive only done 161 miles with quarter of a tank to go ,thats about 260 klms so be lucky to get 390 klms till empty ; i know its running rich i just dont know how to adjust the webber carb or how to tune it

DLM · Post by **DLM** » Thu Feb 19, 2009 3:30 pm

XU-engined PSA cars with autochokes from that period did had a tendency to get thirstier over time. Apart from what's been mentioned above, which I'd check up anyway, 3 more possible factors are:

(1) the general state of cleanliness of the carb itself (which all boils down to whether you have time, facilities and confidence to remove the carb and give it a clean/service)
(2) The health of the waxstat which turns the autochoke off.
(3) How well the coolant system has been bled: the autochoke is controlled by coolant temperature and the autochoke coolant feed is at the very topmost point of the cooling system.

From another point of view, there also used to be a widely-sold manual choke conversion kit for carb BXs and Pug 309/405s - there might still be some knocking around somewhere. There was a fairly universal Haynes carb manual too which had details of the individual carbs, if reference is a problem.

kiwi · Post by **kiwi** » Fri Feb 20, 2009 9:33 am

what Kev forgot to mention on here is that the car travels trips of no more than 2 miles a trip.

Which means

a, Carb dont warm up (even in a hot kiwi summer)

b, the plugs soot up.

kevlights · Post by **kevlights** » Fri Feb 20, 2009 7:51 pm

after a long trip of 100kms then a fornight of traveling to work ;split shifts of four 2.1 klms trips each the fuel usage at the moment is 180 miles ;the red light of low fuel hasnt come on yet but cannt be far away;thats about 290 klms so far,i understand that the short trips will give poor fuel usage due to the cold starting/running not giving the auto choke time to warm up but would hope when hot, on the longer 100 klm run it should be okay; is 290 klms poor milage in this type of driving mostly urban then one rural? what would you expect to get in your car doing similar milage? the car is going to the garage on monday for a WOF and tune up thanks for all your suggestions

kiwi · Post by **kiwi** » Fri Feb 20, 2009 10:27 pm

From a look at some fastidous record keeping would expect you to be around the 5.2-5.6 miles per litre (since it sounds like you have a MPH speedo?)
for the described driving conditions.

How accurately you measure that is not by reading the fuel gauge but by a complete fill of the fuel tank to the point you can see the fuel in the filler pipe and not the inaccurate splash back cut off of the fuel pump.

Reaset the tripo or write down the mileage and next fill up again to the brim calculate it from there.

Two Biggest mistakes people always make are 1, Judging distance according to the Fuel gauge or filling according to the currency worth.

Pretty clear though your not going to get good fuel consumption on that style driving as I pointed out on Aussie Frogs.

BX19 driven on mostly open road returns me 9-10km per litre probably an altitude factor involved and the ossilating roads (Hills) which does involve a climb or descent no matter where I go of around 400 metres per 20km.(95 Octane only)

Our none BX 1500cc Auto returns slightly better on 91 octane fuel of 11 km per litre.

ellevie · Post by **ellevie** » Sat Feb 28, 2009 11:51 am

kevlights wrote:ellevie thanks for your very informative reply;i never thought it could be the distributor; will follow your recommendations as so as i get back from work;ohh bugger its just started raining again so will have to wait for "fix the car again weather" thanks regards Kev

Hi Kev
I haven't actually suggested it might be the distributor --- that just happens to be in the illustration.
If it is indeed an ignition problem and if your coil is like the one in the illustration, then of the things I have suggested the most likely by far is poor contact at the spade connectors on the coil.
David

kevlights · Post by **kevlights** » Sat Mar 21, 2009 8:18 am

thanks for your replys ;have had it to the garage for a gas analysis,which showed the engine was running slightly lean !! had the timing on the carb adjusted ; the mechanic found parts of the carb missing, the wax choke wasnt working properly so is disconected; am starting the car on part throttle ,using the fast idle circuit hoping to avoid the full throttle choke engage;
seems to be running better especially with the correct air cleaner in it now; the car is in good mechanical condition 114,000miles MKI TRS 16
1986 amazing how many reports and reciepts in the glove box and none managed to find the problem;
still looking for a mkI auto choke carb in good nick, is there a modern replacement for the old carb that i can fit to the manifold and tune ; thanks again regards Kev

ellevie · Post by **ellevie** » Sat Mar 21, 2009 11:11 am

Hi Kev,

Any chance of a photo of the carb (and the ignition coil/dist while you're there) ?

DavidRutherford · Post by **DavidRutherford** » Sat Mar 21, 2009 4:22 pm

kiwi wrote:what Kev forgot to mention on here is that the car travels trips of no more than 2 miles a trip.

If this is the case, then I would expect the car to get barely half the fuel economy that it might do otherwise. Cold-start operation on most petrol engines can easily use double the amount of fuel that it would do when up to temperature.

... and it also won't do the engine any good at all. All that excessive fuel will soot it up quite badly, and in a worst-case scenario could mean that you wash all the oil from the bores, creating excessive wear.

For a regular commute of under 2 miles, I'd suggest you use a bicycle.

ellevie · Post by **ellevie** » Sat Mar 21, 2009 5:08 pm

This sounds a bit like my 19TRS which in recent years only does a couple of miles once or twice a week.
For this reason I have installed a manual choke kit. The kits are not so easy to come by these days.

It's surprising how quickly the manual choke can be released after starting to the extent that it is really only acting as a fast-idle for a few minutes at about a fifth to a quarter of its full travel.

kiwi · Post by **kiwi** » Sun Mar 22, 2009 6:16 am

Comparing both my BX 19s together on my religous fuel figures

BX19 (1991) and BX19 (1990) I am surprised to report a noticable differance in Fuel Consumption form basically the same kind of Open Road Running of 20 km minimum per trip.

When I say open road that means little other traffic on undulating twisty bog standard Kiwi Highway (Think B road to give you an idea

)

Heres the big kicker though the car with the better consumption is the one thats a pig to start! Go figure

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