Xantia mpg terrible. Injector issue?

[fotobright]

Hi,

I started a conversation a coupe of weeks ago about running my xantia on veg oil. It was extremely helpful but i've got a another question which relates to my cars current mpg, which I need to solve before running the engine on either veg oil or diesel.

Using a rough mpg calculation it looks like the car is doing about 27mpg, which is terrible! This was on my daily commute, trying to keep the car at a steady 55-60mph to increase the economy.

There is a slight loss of power from the engine over the last year and it definitely blows dark smoke and lots of it when accelerating hard.

This strikes me an injector problem might be the issue but i'm not sure. Is there a check list of issues I should go through to establish why the mpg is so low before getting the injectors looked at.

The car is a 98 xantia estate, 175,000 on the clock, Bosch fuel pump.

Any thoughts would be most welcome

Thanks

[DickieG]

27 mpg is low, the fact that the engine has been losing power and blow dark smoke suggests there is something wrong, it could be injector, an air leak on the turbo pressure side or even a loss of compression, how well does the car engine start on a cold morning, does it need a lot of cranking before it fires and does cold starting differ from how it starts when hot? When running is the engine smooth or misfiring on one cylinder? If you remove the oil filler cap when the engine is running is there a lot of "blow back" as in pressure of exhaust gases out of the cap/crankcase?

Hopefully it'll be something simpler and cheaper such as check the thin rubber pipe that goes to the top of the fuel pump for leaks and the turbo ducting likewise as that will also cause the symptoms you describe.

[fotobright]

Hi, thanks for reply.

The car starts pretty well after I had the glow plugs done before last winter. I'm not seeing any obvious leaks to the fuel pump and there's no obvious leak from the tank.

I'l try the oil filler cap and get back to you. Talking of caps the tank cap has gone so im currently using a temp one with the plastic fins.

I just re-read your posting. Where's the turbo ducting?

[DickieG]

As it starts well that would suggest the compression is OK.

Re the fuel pump I'm talking of air escaping out of the pipes rather than fuel, the pipe that runs to the top of the pump is used for the pump to measure the amount of air being pressurised into the engine by the turbo so in turn how much fuel to inject, an air leak on that pipe will mess the accuracy. With regard to air leaks can you hear the sound of whistling beyond the gentle one a turbo generally makes as that will indicate a leak in the ducting pipes somewhere.

[fotobright]

excellent advice, will check ducting and listen out for extra wistling pitch as i'm just about to head out in car now.

[jgra1]

hmm will keep an eye on this thread foto.. my car is basically exactly the same..
I think as WVO is so cheap I have not being paying attention to mileage.. a huge oversight now as I may have missed something..

I tend to get 4-500 miles per tank, @ a steady 70-80mph.. but everyday driving is much less restrained..
4-500 miles per tank is 28-33 mpg I think.. and that's the best I get :O

John

[DickieG]

Something that has just come to mind is that I had a TD Xantia many years ago doing the same thing, loss of power black smoke etc, I finally found the cause to be the fabric inlet hose under the air filter had collapsed/became blocked which stopped the engine breathing correctly, also check the air filter for cleanliness.

[Peter.N.]

Anything that reduces the ammount of air will cause this problem, try disconnecting the air intake pipe from the manuifold, it should give a considerable reduction in power as you will have lost turbo pressure, if it makes little or no difference that's where your problem lies.

Peter

[fotobright]

Hi, when I changed the air filter and removed the leaves and gunk in the air filter box things improved

[Old-Guy]

....I'm talking of air escaping out of the pipes rather than fuel, the pipe that runs to the top of the pump is used for the pump to measure the amount of air being pressurised into the engine by the turbo so in turn how much fuel to inject, an air leak on that pipe will mess the accuracy.

Yes, but a leak in the pressure sensor pipe to the injector pump will cause the pump to under-fuel rather than to over-fuel with black smoke. As Dickie says, a split in this pipe does seem to be relatively common - as the split gets worse, there's a gradual loss of power (but no noticeable deterioration in consumption). It's not that the volume of air escaping seriously affects the pressure of the inlet duct, but it's the loss of static pressure at the pump so that the pump fails to compensate (with extra fuel) for the boost pressure - the pump behaves as though there's a loss of turbo pressure.

[HDI]

As mentioned above, eliminate the simple stuff first. Check the airfilter, if old or very dirty that would do it. Check the air inlet pipe to the airbox, it takes air from low down so it could have leaves and stuff partially blocking it. If the turbo is on it's way out it can push alot of oil into the intercooler which congeals and blocks it up. Have a look at the turbo outlet pipework to see if it's showing signs of oil.

[Old-Guy]

.... Have a look at the turbo outlet pipework to see if it's showing signs of oil.

It's sure too because the engine breather will blow a certain amount of oil mist into the turbo inlet (this is a TD). If you have noticeable oil consumption and you're worried about the turbo, I'd suggest several checks on how much oil is collecting in the bottom of the inter-cooler.