Anonymous asked in Cars & TransportationMaintenance & Repairs · 2 months ago

Diesel ute blowing smoke smelling of unburnt fuel?

Just did the Valve stem seals on a 1999 Turbo Diesel Ford Courier. Fixed burning oil issue, now smells like unburnt fuel.

Starts up ok in morning, bit chuggy and blows quite a bit of smoke for 2 minutes then will run without smoke but still with the unburnt fuel smell.

Recommendations? Is there a way to adjust the mixture in the engine? It smells very 'lean'?

4 Answers

  • 2 months ago
    Favorite Answer

    Diesels do not have any kind of mixture control.

    Under normal conditions the inlet air is full open / unrestricted to give maximum air charge and compression. That is needed so the oxygen pressure in the cylinders is high enough so the fuel spray ignites spontaneously as it is injected to the cylinder.

    The power is controlled by the amount of fuel injected; the time the injectors are open.

    Newer types may have an inlet throttle device used restrict airflow and reduce boost, to give an engine braking effect, making them react more like petrol engines to the driver - but that is normally open when running normally.

    (Plus the turbo providing additional boost while the engine is under load).

    An obvious cause of uneven firing is worn or clogged injectors, or low pressure to the injectors.

    That would typically cause black smoke as the oversize fuel droplets do not fully burn.

    Another possibility is low compression, meaning one one or more cylinders are not always firing even though fuel is being injected.

    The "chugginess" does imply it's not firing evenly. 

    Try checking the exhaust manifold temperature at each port immediately after it's started, or just run it say 15 - 30 seconds from cold then stop it again,  and check the exhaust at each cylinder. Some should be noticeably cooler or even completely cold if it's not firing on those; they are the ones to examine more carefully.


    When you  were doing the valve stem seals, did each valve go back in it's original position, and/or  did you grind them in?? 

    If the valves are not seating properly that could be causing compression problems.

  • ?
    Lv 7
    2 months ago

    Sounds like you have a misfire on a cold start. First of all, presuming your engine has glow plugs, are you using them correctly? That is, waiting for the glow plug light to go out before you start.  If you are using them properly, you may have a faulty glow plug.  That can cause a misfire on a cold start, where most of the cylinders fire up as they should but the one with the dud glow plug is reluctant.

    The next thing is an injector problem, where one of them isn't working properly and its cylinder doesn't fire correctly for while.

    Both can be checked by a diesel mechanic.

  • Anonymous
    2 months ago

    Do you have glow plugs? Many little engines do.  The key is turned SLOWLY IN STAGES.  First stage, all the dash lights light up.(the lighting up is to prove the bulbs are still good)  Look for the light that looks like a coil spring or a light bulb filament in a bulb.  It should be yellow.  Now wait until the bulb light goes out and THEN START THE ENGINE.   There also should be a black button(maybe with an S on it) . This pulls out like a choke did on some of the carburetor cars.  You MUST pull this out first.  This is a cold start button(cold is when the vehicle has not been running for 6 hours) That button advances the injection timing by a HAIR)  . No pull = chuggy and smoky.  

    , No glow plugs = chuggy & smoky.

      DO not touch the throttle(gas pedal) while you are cranking the engine. Everything is set to start.  Your gas foot is NOT NEEDED.  The vehicle will start faster.  Once the engine has been started and is running you slowly can push in the S button.  Maybe 5 minutes, though sometimes I forget and it stays out for the whole day.

    Really, if you have an owner's manual, READ IT.   Diesels are basically all the same in their operation.  So you know the stuff I am guessing at as my several vehicles and trucks did have GP and did have an Injection advance knob.(S)

    Have you checked/changed the air filter for the engine?  Many forget to check that.

    You can't smell a lean diesel.  Lean means NO SMELL because it burnt ALL THE FUEL.  If you smell it it is because not all the fuel is being burnt in the engine and some ends up being burnt in the exhaust pipe or not being burnt at all.

    You can't adjust the fuel injection pump. Not unless you got $5000.00+ worth of testing equipment.   Yeah it is something the shop has to do.  It is a very exacting engine.  You can't monkey around with it.   Timing has to be DEAD ON.   Nothing you can hear or feel.

    .I have also had NONE GLOW PLUG diesels, and ran them (Caterpillar bulldozer) from 1954.

    . you MAY ALSO HAVE A BLOCK heater.  Check the front of the engine and look for a 120Volt AC cord-plug male end. near the radiator or fender or bumper.  This would be the end that plugs into an extension cord which you plug into a wall outlet.  Even an hour does a lot to warm up the oil in the crankcase and coolant so the vehicle starts easier.  As the manufacturer's don't know where the car will end up, it may be standard equipment.

    . Sweet, as it pulls less on the battery.

  • 2 months ago

    funny thing this ..been driving for close to 60 years ..never ever smelt unburnt diesel fuel ....this smoke ..what colour ?..injectors problems its black ...oil blue ..water white ..and lean diesel mix does not exist 

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