Automotive Forums

Dear Sir, I have a Chevrolet Silverado 1996, Model (K20953).

The car was extremely difficuly to start, after a full analysis of the vehicle it was discovered that the injection pump was faulty, after installing a new pump the car starts directly. After the car has been running for about 15 to 20 min it starts to blows enormous amounts of white smoke from the exhaust. This problem was coming from the installation of the new injection pump as the settings weren't correct, after re-adjusting the pump the white smoke problem stopped.

Then a new problem was discovered, after driving the car for about 10 miles the car losses power and the engine runs roughly (all gauges are normal not indicating that there is any problem with the motor), if you try to accelerate you have no power, if you then turn the car off for about 5 to 15 min you can then start the car as normal with no problems, you can then drive  for another 6 miles and the same problem occurs.

I have received advice that the injectors are faulty and not performing to the full capicity, if the injectors were faulty then the motor would be hard to start when cold. When a diesel engine blows white smoke, that indicates un burnt fuel. It usually is accompanied with a strange sweet type of smell. Two things can cause white smoke. One is low on compression, which means that the motor is worn out. If that is the case then the motor is hard to start when cold, because that is when the compression is the least and if you get it going and it heats up and the expansion of the pistons with heat increases the compression and the smoke normally lessens.

In this case I have the opposite situation. The second reason for white smoke is incorrect mixture of air to fuel. As this is a computerised engine, I am not sure just what function the computer exercises on the mixture. Does the computer control the correct amount of fuel through the injectors.

When the motor is cold it starts easily and runs perfectly for a given period.That means that something is going wrong when the engine either gets to a certain temperature or the computer takes over on the air to fuel ratio. It could be turbo or it could be computer mismanaging the mixture, is this possible ????

I tend to think that the problem rests somewhere in the computer system, but I cannot be sure. If it is the turbo, then it would have to mean that the turbo is somehow sticking at temperature and ceasing to inject air into the motor. I have never seen that happen, but you never know.

Getting back to the injectors, as I said above , if they were faulty the engine would be hard to start when cold, but it still may be possible that the computer if it takes over the fuel to air ratio is interferring with the flow of fuel and air, which may give the indication that something is wrong in the injection system, (which it is), but I would bet 100 to 1 that it is not the injectors themselves.

I would be interested in your advice regarding the above, Many thanks.  

It would be very hard to diagnose a problem without having actual scan data, compression readings, etc...  There's no point guessing what's wrong with your motor - you'll spend more money throwing the wrong parts at it than you will taking it to reputable diesel shop and paying for a little diagnostics.  

If your not getting enough fuel to the injection pump it would also give you a good indication why the previous one failed. Usually problems with cold starts are indications of bad glow plugs or air getting into the fuel system. Some diesel engine utilize a cat and nothing could be worse for problems (probably your problem). I've replaced a lot of injectors that were faulty but more than most of the time misfires were present. Usually a worn out injector will open at an lower/early pressure from pump and the result will be low max rpm and weak hp. Some of the newer engines utilize a very thin top ring and dirt that gets around the air box (which is made for a cheap toy) will break the upper rings. You can see just how well off a turbo diesel is by inspecting the fins on the impeller for wear and doing a compression check.  

I just purchased a rebuilt Adsit engine for my 1991 Mercedes Benz 350SD.  I am having similar problems.  The cold startup is fine, runs great for about 10 miles, then it bogs down and starts putting out the white smoke and gets progressively worse.  The smoke increases upon acceleration.  If I turn the car off for 10 min and restart, it runs normally with no problems.
    If I return the engine to Adsit for replacement or repair (only option-no refunds), I have to pay $500 to ship it roundtrip and another re-install for $2,500.  I'm thinking of trying to get it repaired on my own, because there's no guarantee that Adsit repaired engine will work and then I'm out $3K.
    Have you found any new information out since you posted on 9/18?  I'm looking for any leads.  Thanks.