Volcane - Only 38 MPG? Cold start enrichment fault

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PJLarge
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Volcane - Only 38 MPG? Cold start enrichment fault

Post by PJLarge »

My new ZX is much worse on fuel than the old one even though it's done only half the mileage. Filled to the brim, the old car would easily do 250 miles on the first half of the tank, up to about 480 before I would refill. This one just about makes 200 miles to the half way mark. I thought it may have just been the gauge doing its usual random readings, so I filled it up tonight back to the brim and worked it out - 38 MPG.
The car is used 98% of the time on dual carriageway at 70 - 80 mph so it should be pretty good. I'm doing about 75 miles a day on the round trip and I'm not driving it any differently to the old one. I did the glow plugs, fuel, air and oil filters on Sunday, so it's had a decent service. Brakes aren't binding, tyre pressures are spot on, so what could be causing such a high consumption? I can get better than that out of a petrol!
The only thing I can think of is that the cold start thing on the pump doesn't seem to be working as it idles at 950 rpm regardless of temp. The old one used to sit at 750, so there's definately something going on there. I tried to move the lever whilst I was cursing that damn glow plug behind the pump but it seemed pretty tight. I know this can effect consumption, but to this degree? Is there a procedure for setting it somewhere? It's a Bosch pump BTW.
If I can't get it any higher I'll be moving this one on in short order. It totally defeats the object of having an economical commuter car!
Thanks for the advice,
Phil.
oilyspanner
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Post by oilyspanner »

I dont think i get much more than that from either my Volcane or my BX, it may have been gently driven for a long time and settle down?
Stewart
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Post by P 2501 »

You should definately be getting better economy than that. I have the same engine in a 306 and i can easily get 600-650 miles from a tank and if i am very careful with the right foot around 700. With the zx being slightly lighter you should be around the same or better.
It sounds as if your old ZX may have had a problem as well, as 480 to a tank is pretty poor.
WRT the cold start device i think it should idle at around 1100 ish when cold and 800 ish when up to temp. If the cable seems nice and tight when engine is cold then slack when hot, then i don't see a prob...
What about the injectors? poor spray pattern could cause 38mpg. Difficult to DIY test however.
Good luck!
jeremy
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Post by jeremy »

Firstly its well worth having a good look underneath the car to see if there are any leaks. I sa this having found a vent pipe on the top of the tank of our ZX 1.9D had split right on top of the tank right out of site. If you have a leak the tank will be wet and you will probably have spots of diesel on the back of the car.
Our ZX fuel gauge goes into the red with about 5 gallons left in the tank. I know this is true as the thing read empty when I did the leak and there was about 1/2 a tank in it then!
Your idle sounds high. Moving the cold start lever should make a difference and you may have to slacken the cable to see what is happening. Some light lubricant round the levers may help if they are stiff. I think the waxstat device operating this mechanism fails in the hot position - certainly mine did. What influence this mechanism has on fuel consumption depends how it works. On the Roto-diesel pump the cold start was originally simply achieved by adjusting the stop position (ie opening the throttle) but later ones (BX TD + all ZX) the injection timing is advanced. I don't know how your Bosch pump works but advanced injection (ie incorrect timing for a hot engine) would affect consumption, make the car slow and possibly produce smoke.
If you have injector problems I would expect the exhaust to smell and smoke. If it doesn't your injectors are probably ok. A cleaner may work but otherwise its time to have them replaced or overhauled.
Jeremy
PJLarge
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Post by PJLarge »

Thanks for the help so far... The car doesn't smoke at all, I'll go and have a look at the cold start device in a while and see what it does. I'm confident it's related to that as the idle is so high and there's not a whole lot else it could be. I'll run a bottle or two of injector cleaner through it as well though as well as give it an Italian tune-up.
Phil.
rossd
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Post by rossd »

The coldstart shouldnt have that much of an effect on consumption, as any advance in timing made by the coldstart lever is cancelled out above 1600rpm. My old 306TD used to get about 480 miles from a tank, anything from 42 - 46 mpg was the norm. My HDi gets about 50mpg on the same commute.
Bad consumption could be a multitude of things. For starters if its been driven gently for any period of time, an italian tune up could help blow the crap out and consumption after that ay improve....
robsons
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Post by robsons »

I get the same economy out of my Volcane and it's all motorway 3500rpm (most of the time) - always passes emmisions tests and doesn't smoke either.....Some people here seem to think this is the norm
PJLarge
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Post by PJLarge »

A follow up -
Prior to my buying it, the car had done maybe 5000 miles in the last two years. I've been keeping an eye on the economy and it has improved a little, it's now up to 42MPG after I ran a shot of injector cleaner through it on the last 1/4 tank, gave it a good run on the governor for 5 miles or so and sorted the cold start device - it was jammed on hence the high idle. From the brim of the tank, I can now get 450 miles before the light comes on which I still feel is a little on the low side considering other peoples quotes of 550 miles + to a tank. How big is the tank anyway? This morning it took 47 litres which had taken me 441 miles.
Thanks,
Phil.
q_007
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Post by q_007 »

I got 350 miles to a full tank
Something definatly not right with mine!!!
Anyone near Heathrow that can tune it up for me?
Q
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VLL
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Post by VLL »

350-400 miles is the norm for mine, doesnt seem to make any difference how I drive it or where, its consumption has been pretty much constant for the last 6 years so either i'm getting crap mileage or your expecting too much.
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Post by Sl4yer »

I know mine usually did between 44 and 48MPG, most of that being on the motorway. I never got more than about 450 miles on a tankful before my bottle went and I had to fill up. My previous 1.4i ZX had fuel pickup problems towards the bottom of the tank, and I don't want the Volcane cutting out at an inconvenient moment, like in the outside lane of the M6!
ZX fuel gauges aren't the best - I think its better to be safe than sorry, especially with a diesel.
jeremy
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Post by jeremy »

My ZX 1.9D reads empty when there are about 4 or 5 gallons left in the tank - and puts the warning light on. I suppose I could bend the float arm but it seems a bit like hard work especially with that wonderful back seat!
The capacity is a touch under 12 gallons.
jeremy
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Post by razzleuk »

I have a 1997 306 TD that also has the cold start advance stuck on. I am getting 41-44mpg this winter, and I was getting 46ish regularly back in the summer. I disconnected the EGR last year which I reckon has given me 2-3mpg better economy.
With changing up at 2.5k revs I have had 50.8mpg out of this car, that was 576 miles without the light coming on even :-)
I haven't fixed the cold start advance because the car feels more powerful like that, I don't know if it's my imagination :-) I have tweaked my on-boost fuelling too which may be clouding my judgement, although this car always felt quicker just before it was warmed up..
Raz.
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