2. Air Induction System Problems There are three major types of air induction system problems (or
complaints). • Engine performance
• Mechanical failures
3. Air Induction System Problems Engine performance problems can be in the air induction system, the fuel system, or the basic engine.
The typical engine performance complaints are: low power, low response, excessive smoke, high fuel consumption, low boost or high exhaust temperatures.
4. Air Induction System Problems Leakage problems can occur as air leaks on the inlet side of the system, exhaust gas leaks, oil leaks in the turbocharger or its lubrication system, or water (coolant) leaks from or around the aftercooler.
5. Air Induction System Problems Mechanical failures can be noise in the turbocharger, damage to pipes, lines, or other components, or foreign material in the system.
When a damaged part or component is removed, it is always necessary to find the reason for the failure before a replacement part is installed.
6. Ask the Operator When engine service or repair is necessary, it is a good idea to talk to the operator if possible.
Remember, only the customer can tell the serviceman first hand what the actual symptoms are.
Listen to their complaints, and if necessary, ask questions that will help with the analysis of the problem. Try to determine when they should clean or change the air cleaner elements and how they are serviced.
The operator should also be asked how the problem manifests itself (Is there any accompanying noise or smoke.)
7. Visual inspection The first step to solving an air induction system problem is a visual inspection.
A visual inspection of the air induction system does not take very long to perform, and it can possibly prevent a large amount of unnecessary work.
A good place to start is to check the exhaust stack to see if the engine has forced (blown) any oil out of the stack.
This condition can be caused by oil leakage past worn turbocharger seals or by a plugged oil drain line from the turbocharger.
It can also be an indication of a problem in another area in the engine, such as cracked or broken piston rings, or a plugged crankcase breather.
If the engine is run at idle for a long period of time, diesel fuel can also be forced (blown) out of the exhaust stack.
8. Restriction Indicator Check the air cleaner service indicator to see if it displays red and how much.
If it is above the limits for that engine, reset the indicator and run the engine under load to determine if the reading was accurate.
If the indicator once again shows unsatisfactory readings, clean or replace the air filter element.
While the air filter is removed, check for any other restrictions within the revealed piping.
It is also a good idea to inspect the service indicator for cracks, dirt, and other damage.
9. Look around the air cleaner housing for any damage (dents) or holes.
Be sure that the cover is on tight.
Look for obstructions of the flow of air into the inlet to the filter housing.
10. Checking Clamps Check all the clamps to assure they are properly installed, torqued, and are not broken.
Be sure that there is no visible damage to the inlet manifold gasket.
If the machine is equipped with an aftercooler, inspect the piping and seals between the turbocharger and the aftercooler for any leakage.
Frequently, leakage can be identified by soot trails coming from a joint.
At the same time, look around the gasket between the piping and the aftercooler for any other signs of leakage.
11. Aftercoolers Look around the aftercooler and inlet manifold for any signs of either water (coolant) leakage or air leakage.
Inspect the coolant lines, hoses, and connections for any damage that can cause leakage or restriction of the coolant flow .
Make sure that all clamps, bolts, and fittings are properly tightened.
Check for visible cracks in the aftercooler .
12. Audio-visual checks The second step to solving an air system problem is to make audiovisual checks while the engine is running.
Start the engine and listen to how it runs without a load at low idle, half speed, and at high idle rpm.
Listen for turbocharger noise or air leaks, and see if the engine runs smoothly or roughly.
If possible, operate the machine to learn if it has any other problems under a load.
13. Exhaust Look to see if the engine smokes. If it does, observe the color of the smoke that comes out of the exhaust stack.
Black smoke is an indication of too much fuel and/or not enough air for maximum engine performance.
Blue smoke is an indication that oil has been burned in the combustion chamber.
A quick puff of smoke that quickly clears up is O.K.
A sign of trouble would be smoke that does not quickly clear up, or unusually dark or heavy smoke.
14. Checking for Air Leaks There are several methods that can be used to find an air leak in the inlet or vacuum side of the air system.
To find an air leak around the O-ring seals or hose/tube coupling between the air cleaner and the turbocharger, put a bead of petroleum jelly or grease around the joint and operate the engine.
If possible, run the engine with a load (such as torque converter stall or against the brakes). I
f there is an air leak, a hole will form in the bead.
15. Checking for Air Leaks To find an air leak caused by a crack, hole or joint leak in the inlet system before the turbocharger, spray a small amount of ether around the piping with the engine running.
If there is an air leak, the engine will run a bit faster and possibly knock.
This is done with the engine in operation without a load.
16. Checking for Air Leaks To find a leak in the system after the turbocharger (inlet or exhaust), soapy water or shaving cream can be used.
Just spray the soapy water solution around each of the joints while the engine is running.
This procedure works a bit better if the engine is running at least 1000 rpm.
Be careful that the fan does not blow debris into your eyes.
17. Checking for Air Leaks Performance problems can also be caused by the restriction of air flow to the engine.
Remove the precleaner and look for dirt and foreign material that can cause a reduction of air flow.
Inspect the seal on the outer (primary) filter element and the gasket on the inner (secondary) filter element.
18. Checking for Air Leaks If the air cleaner housing is bent or damaged, air and dirt can flow around the filters and directly into the engine.
To check the housing, first put an application of petroleum jelly or a similar product around the gasket and seal area.
Then, install the filters, and put the cover in position on the housing.
19. Checking for Air Leaks Start the engine and spray a small amount of carpenter’s chalk (blue or red powdered chalk) into the precleaner.
If the air cleaner housing is not damaged, the filters will remove the chalk from the inlet air.
20. Checking for Air Leaks If the air cleaner housing is excessively damaged or bent, the chalk will leave marks or "tracks" in the area of the air leak.
While it is not normal procedure to add foreign material to the air induction system, an air leak of this type can cause a large amount of engine damage if the leak is not found.
In the final analysis, a small amount of chalk for testing is better than a large amount of dirt on the job.
21. Checking for Air Leaks If no leaks were found, run the engine at half speed with no load.
Listen to the sound of the engine to determine if you hear any air leaks that have not previously been discovered.
Turn the engine off.
As the engine comes to a stop, listen to the sound of the turbocharger as its speed decreases. Listen for the sound of wheel contact (rubbing) against the turbocharger housing.
Also, foreign material in the system can cause parts to break off and make noise.
22. Mechanical measurements If the problem is not found by the previous two methods, then we must go to the more time consuming method –
With this method we will need to use physical tools instead of our eyes and ears.
23. Mechanical measurements A practical method to check for a dirty or plugged aftercooler is to install temperature probes in the inlet manifold and the temperature regulator housing; then run the engine under a load.
The temperatures of the inlet air before and after the aftercooler should be within the specifications in the service manual.
If the inlet air temperature is too high, the flow of the cooling media has possibly been restricted.
24. Mechanical measurements With the use of a Pressure Group and a Multitach, we can measure manifold pressure and engine rpm.
The basis for this performance analysis is the fact that (l) if the engine is in good condition, (2) if all adjustments are correct, and (3) if the correct parts are installed, the inlet manifold pressure is in direct relation to the development of power.
25. Mechanical measurements The inlet manifold pressure is an indication of the amount of air supplied to the engine.
Run the engine until it gets to normal operating temperature. With the engine at high idle, load the engine with the use of a chassis dynamometer or the vehicle brakes.
Load the engine such that it runs at engine speeds found on the TMI Performance Information.
Plot the different pressures at the selected rpm.
Compare these numbers in the specification, taking into account the appropriate tolerances
26. TMI Performance Specifications Check the TMI Performance Information for the normal full load rpm, and if necessary, adjust set point to get the correct value.
Then, record the inlet manifold pressure, engine speed, fuel pressure, air inlet pressure, and exhaust manifold pressure under load.
The primary checking point would be the engine’s rated speed.
These values can be compared to the standards.
Remember to apply proper tolerances to these values.
27. High Manifold Pressure If the inlet manifold pressure is higher than the specification, check for the following:
- Deposits on the turbocharger nozzle
- Wrong governor or rack settings
- Wrong nozzles
- High inlet air temperature to engine
Do not ignore a high inlet manifold pressure because it is an indication of a problem which can cause early engine or turbocharger failure. •Deposits on turbo nozzle
Wrong governor setting
High inlet air temperature
28. Low Manifold Pressure If the inlet manifold pressure is lower than normal, there is not enough air and/or fuel flow to the engine.
This can be caused by:
- A restriction in the air induction system, either on the inlet or exhaust side
- An air leak in the induction or exhaust system
- Low fuel delivery
Pressure measurements can then be made for each component to find the exact location of the problem. Restriction within air system
Low fuel delivery
29. Causes of Turbocharger Failure • Lack of lubricant
• Contaminated lubricant
• Foreign objects
31. Lab Homework