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Goce

Increase fuel consumption on a diesel

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Lately i've noticed an increase in fuel consumption on my daily driver, it's an mechanical indirect injection turbo diesel XUD 11 ate when i first did the engine conversion on this car i had the pump reseal, and also turn down to get better fuel economy, the first 2-3 years i put on close to 200 000 km on it with around 6-7l/100km and from then has steadily increased now i'm around 10l/100km and i've done close to 350 000 km in 5 years, the engine has more then 2 million km on it and has no issues still starts first turn doesn't smoke at all, has good power, my question is can the fuel pump come out of adjustment and cause increase in fuel consumption, or is there something else that can cause such an increase, i'm sure is not leaking fuel and if is out of adjustment it should smoke like crazy. Any ideas or suggestions, apart getting a new car?

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Just a guess - but I'd wonder if the turbocharger is building boost as efficiently as it did previously.  If it's not boosting as efficiently, or to a lower level then you might assume that you're using more fuel to compensate for the reduction in boost.  

Could also be the pump as you say - if it's gotten richer you may only see it in your EGTs rather than in increased smoking, but without knowing them before you couldn't verify a changed.  You might see higher than normal temps which would suggest it's a bit rich.

Rabin

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The turbocharger is definitely not building boost as efficiently, but is still making 0,9-1 bar max, but is extremely laggy, begins to spool at 2000 rpm is at 0,5 bar at 2200 rpm, gets to 0,9-1 bar at 2600 rpm and holds up to 3200 rpm, above 3600 rpm there is no power. But this is a mechanical injection, low boost low fuel more boost more the diaphragm let's fuel, there is no smoke to show rich mixture, the car has no catalytic converter to prevent it from smoking, this has me confused, the oil doesn't smell of diesel, but i'm changing it every 2 weeks or every 7000 km this  is probably why this engine has lasted so long. This engine has hydraulic lifters and they, fuel injector and turbocharger has been on this engine for more than a million km, i know this is extreme high mileage for an engine but they are not showing any signs of malfunctioning, any test i can do or some thing to check?

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5 hours ago, Goce said:

low boost low fuel more boost more the diaphragm let's fuel

This also works the other way around, with an old stiff diaphragm it's hard to build boost and there is no smoke.

I can't remember by how much but fuel economy was improved when the stiff diaphragm of my Lucas pump was replaced.

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With the turbo not building boost as effectively I'd argue the engine is working harder as it's simply not as efficient as it would be with boost.  Combine with possible stiff diagram SRDT mentioned and that would be a pretty good hypothesis.  :)

Rabin

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I haven't even thought about that diaphragm and is only 4 bolts to remove, i'll check it, but it should have been replaced when the pump was resealed couple of years back, what should it be like, like a diaphragm from a mechanical fuel pump?

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I've checked the diaphragm, soft, rubbery textile material no tears i used my vacuum gauge and is not leaking is there way to check the fuel pump without removing it from the engine?

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