N14 Base Engine Troubleshooting and Repair Manual – t00-004   Troubleshooting Overview

Engine Noise Diagnostic Procedures – General Information

When diagnosing engine noise problems, make sure that noises caused by accessories, such as the air compressor and power takeoff, are not mistaken for engine noises. Remove the accessory drive belts to eliminate noise caused by these units. Noise will also travel to other metal parts not related to the problem. The use of a stethoscope can help locate an engine noise.

Engine noises heard at the crankshaft speed, engine rpm, are noises related to the crankshaft, rods, pistons, and piston pins. Noises heard at the camshaft speed, one-half of the engine rpm, are related to the valve train. A hand-held digital tachometer can help to determine if the noise is related to components operating at the crankshaft or camshaft speed.

There is not a definite rule or test that will positively determine the source of a noise complaint.

Engine driven components and accessories, such as gear-driven fan clutches, hydraulic pumps, belt-driven alternators, air-conditioning compressors, and turbochargers can contribute to engine noise. Use the following information as a guide to diagnosing engine noise.

Main Bearing Noise

(Refer to Engine Noise Excessive – Main Bearing symptom tree)

The noise caused by a loose main bearing is a loud dull knock heard when the engine is pulling a load. If all main bearings are loose, a loud clatter will be heard. The knock is heard regularly every other revolution. The noise is the loudest when the engine is lugging or under heavy load. The knock is duller than a connecting rod noise. Low oil pressure can also accompany this condition.

If the bearing is not loose enough to produce a knock by itself, the bearing can knock if the oil is too thin, or if there is no oil at the bearing.

An irregular noise can indicate worn crankshaft thrust bearings.

An intermittent sharp knock indicates excessive crankshaft end clearance. Repeated clutch disengagements can cause a change in the noise.

Connecting Rod Bearing Noise

(Refer to Engine Noise Excessive – Connecting Rod symptom tree)

Connecting rods with excessive clearance knock at all engine speeds, and under both idle and load conditions. When the bearings begin to become loose, the noise can be confused with piston slap or loose piston pins. The noise increases in volume with engine speed. Low oil pressure can also accompany this condition.

Piston Noise

(Refer to Engine Noise Excessive – Piston symptom tree)

It is difficult to tell the difference between piston pin, connecting rod, and piston noise. A loose piston pin causes a loud double knock which is usually heard when the engine is idling. When the injector to this cylinder is cut out, a noticeable change will be heard in the sound of the knocking noise. However, on some engines the knock becomes more noticeable when the vehicle is operated on the road at steady speed condition.

Driveability – General Information

Driveability is a term which in general describes vehicle performance on the road. Driveability problems for an engine can be caused by several different factors. Some of the factors are engine related and some are not.

Before troubleshooting, it is important to determine the exact complaint and whether the engine has a real driveability problem or if it simply does not meet driver expectations. The Driveability-Low Power Customer Complaint Form is a valuable list of questions that must be used to assist the service technician in determining what type of driveability problem the vehicle is experiencing. Complete the checklist before troubleshooting the problem. The form can be found at the end of this section. If an engine is performing to factory specifications but does not meet the customer’s expectations, it must be explained to the customer that nothing is wrong with the vehicle and why.

The troubleshooting symptom charts have been set up to divide driveability problems into two different symptoms: Engine Power Output Low and Engine Acceleration or Response Poor.

Low power is a term that is used in the field to describe many different performance problems. However, in this manual low power is defined as the inability of the engine to produce the power necessary to move the vehicle at a speed that can be reasonably expected under the given conditions of load, grade, wind, and so on. Low power is usually caused by the lack of fuel flow which can be caused by any of the following factors:

• Lack of full travel of the throttle pedal
• Failed boost sensor
• Excessive fuel inlet, intake, exhaust, or drain line restriction
• Loose fuel pump suction lines.

Low power is not the inability of the vehicle to accelerate satisfactorily from a stop or the bottom of a grade. Refer to the performance tree Engine Power Output Low for the proper procedures to locate and correct a low power problem. The chart starts off with basic items which can cause lower power.

Poor acceleration or response is described in this manual as the inability of the vehicle to accelerate satisfactorily from a stop or from the bottom of a grade. It can also be the lag in acceleration during an attempt to pass or overtake another vehicle at conditions less than rated speed and load. Poor acceleration or response is difficult to troubleshoot since it can be caused by factors such as:

• Engine or pump related factors
• Driver technique
• Improper gearing
• Improper engine application
• Worn clutch or clutch linkage.

Engine related poor acceleration or response can be caused by several different factors such as:

• Failed boost sensor
• Excessive drain line restriction
• Throttle dead band.

Refer to the performance tree Engine Acceleration or Response Poor for the proper procedures to locate and correct a poor acceleration or response complaint.

Response Test

This procedure can be used for testing response on heavy-duty CELECT™ and CELECT™ Plus engines.

For this test, a boost pressure gauge, associated plumbing lines, and a stop watch will be needed.

1. Attach the tractor to a loaded trailer (GVW) and must be 65,000 to 80,000 pounds.
2. Make sure the engine is warmed to operating temperature.
3. Determine the full boost pressure at torque peak engine speed while applying full throttle. The trailer brakes can also be applied for additional loading, if required. Record the boost pressure at torque peak engine speed.
4. Perform the coast down test. Select a secondary road that is level and has minimal traffic. Accelerate the vehicle up through the gears to direct gear (1 to 1) and to an engine speed at least 300 rpm above torque peak engine speed. From this point, allow the vehicle to coast down to torque peak engine speed then snap the throttle. Measure the time required to develop 50 percent of torque peak boost (determined in Step 3 above).
5. Repeat Step 4 two more times for a total of three data points.
6. Calculate the average time to 50 percent boost: Average time to 50 percent boost = (time 1 plus time 2 divided by time 3)/3.

The average time must be 3 seconds or less for acceptable performance.

Driveability/Low Power – Customer Complaint Form

Customer Name/Company __________________________________________________________ Date ________________

1. How did the problem occur? Suddenly ________ Gradually ________
2. At what hour/mileage did the problem begin? Hours ________ Miles ________ Since New ________

• After engine repair? Yes ________ No ________
• After equipment repair? Yes ________ No ________
• After change in equipment use? Yes ________ No ________
• After change in selectable programmable parameters? Yes ________ No ________
• If so, what was repaired and when?______________________________________________________________
• Does the vehicle also experience poor fuel economy? Yes ________ No ________

Answer questions 4 through 8 using selections (A through F) listed below. Circle the letter or letters that best describes the complaint.

1. Compared to fleet
2. Compared to competition
3. Compared to previous engine
4. Personal expectation
5. Will not pull on hill
6. Will not pull on flat.

A B C D E F

• Can the vehicle obtain the expected road speed? Yes ________ No ________
• What is desired speed? rpm/mph ________
• What is achieved speed? rpm/mph ________
• GVW ________________

A B C D

• Is the vehicle able to pull the load? Yes ________ No ________

When?

• ________ In the hills
• ________ With a loaded trailer
• ________ On the flat
• ________ Other ___________________________________________________________________________________

If question 4 or 5 was answered no, fill out the Driveability/Low Power/Excessive Fuel Consumption Checklist and go to the Low Power performance tree. A B C D E F

• Is the vehicle slow to accelerate or respond? Yes ________ No ________
• From a stop? Yes ________ No ________
• After a shift? Yes ________ No ________ rpm ________
• Before a shift? Yes ________ No ________ rpm ________
• No shift? Yes ________ No ________ rpm ________

A B C D

• Does the vehicle hesitate after periods of long deceleration or coasting? Yes ________ No ________
  rpm ________

If question 6 or 7 was answered Yes, fill out the Driveability/Low Power/ Excessive Fuel Consumption Checklist and go to the Poor Acceleration/Response performance tree.

A B C D E F

Additional Comments:

______________________________________________________________________________________________________________________________________

______________________________________________________________________________________________________________________________________

______________________________________________________________________________________________________________________________________

This form can be copied for convenience.

Driveability/Low Power/Excessive Fuel Consumption – Checklist

Vehicle/Equipment Specifications

Year, Type and Model: ____________________________________________________________________________________

Transmission (RT 14609, etc.): ________________________, Duty Cycle: ________________________________________

Rear Axle Ratio, No. of Axles: ________, Application: Industrial ____, Marine ____. Genset ____. Automotive ____

Typical GVW: _________________________, Engine Rating: _________________________

Trailer Type and Size: _______________________________________, Height: __________, Weight: __________

Tire Size (11R x 24.5, Low Profile, etc.) ________________________________________________________

Tire Type: Radial __________, Standard Tread __________, Extra Tread __________

Fan Type: Direct Drive __________, Viscous __________, Clutch __________

Power Steering: Yes ________ No ________
Air Conditioner: Yes ________ No ________
Air Shield: Yes ________ No ________
Freon Compressor: Yes ________ No ________

Additional Comments:

__________________________________________________________________________________________________________

__________________________________________________________________________________________________________

This checklist can be copied for convenience.

Fuel Consumption – General Information

The cause of excessive fuel consumption is hard to diagnose and correct because of the potential number of factors involved. Actual fuel consumption problems can be caused by any of the following factors:

• Engine factors
• Vehicle factors and specifications
• Environmental factors
• Driver technique and operating practices
• Fuel system factors
• Low power/driveability problems.

Before troubleshooting, it is important to determine the exact complaint. Is the complaint based on whether the problem is real or perceived, or does not meet driver expectations? The “Fuel Consumption — Customer Complaint Form” is a valuable list of questions that can be used to assist the service technician in determining the cause of the problem. Complete the form before troubleshooting the complaint. The following are some of the factors that must be considered when troubleshooting fuel consumption complaints.

1. Result of a Low Power/Driveability Problem: An operator will change driving style to compensate for a low power/driveability problem. Some things the driver is likely to do are, (a) shift to a higher engine rpm or (b) run on the droop curve in a lower gear instead of upshifting to drive at part throttle conditions. These changes in driving style will increase the amount of fuel used.
2. Driver Technique and Operating Practices: As a general rule, a 1 mph increase in road speed equals a 0.1 mpg increase in fuel consumption. This means that increasing road speed from 50 to 60 mph will result in a loss of fuel mileage of 1 mpg.
3. Environmental and Seasonal Weather Changes: As a general rule, there can be as much as a 1 to 1.5 mpg difference in fuel consumption depending on the season and the weather conditions.
4. Excessive Idling Time: Idling the engine can use from 0.5 to 1.5 gallons per hour depending on the engine idle speed.
5. Truck Route and Terrain: East/west routes experience almost continual cross winds and head winds. Less fuel can be used on north/south routes where parts of the trip are not only warmer, but see less wind resistance.
6. Vehicle Aerodynamics: The largest single power requirement for a truck is the power needed to overcome air resistance. As a general rule, each 10 percent reduction in air resistance results in a 5 percent increase in mpg.
7. Rolling Resistance: Rolling resistance is the second largest consumer of power on a truck. The type of tire and tread design have a sizeable effect on fuel economy and performance. Changing from a bias ply to a low profile radial tire can reduce rolling resistance by about 36 percent.

Additional vehicle factors, vehicle specifications, and axle alignment can also affect fuel consumption.

Fuel Consumption – Customer Complaint Form

Customer Name/Company __________________________________________________________ Date ________________

Answer the following questions. Some questions require making an X next to the appropriate answer.

1. What fuel mileage is expected? ________ Expected mpg
2. What are the expectations based on? Original mileage ________, Other units in fleet ________, Competitive engines ________Previous engine owned ________, Expectations only ________, VE/VMS report ________
3. When did the problem occur? Since New ________, Suddenly ________, Gradually ________
4. Did the problem start after a repair? Yes ________ No ________ If so, what was repaired and when? ____________________________________________________________
5. Is the vehicle also experiencing a Driveability problem (Low Power or Poor Acceleration/Response)? Yes ________ No ________

If answered Yes, fill out the Driveability/Low Power/Excessive Fuel Consumption Checklist and go to the Engine Power Output Low performance tree.

6. Is the problem seasonal? Yes ________ No ________
7. Weather conditions during fuel consumption check? Rain _____, Snow _____, Windy _____, Hot Temperatures _____, Cold Temperatures _____
8. How is the fuel mileage measured? Tank _____, Trip _____, Month _____, Year _____ Hubometer _____, Odometer _____
9. Are accurate records kept of fuel added on the road? Yes ________ No ________
10. Do routes vary between compared vehicles? Yes ________ No ________
11. Have routes changed for the engine being checked? Yes ________ No ________
12. What are the loads hauled, compared to comparison unit? GVW _______________ Heavier ________, Lighter ________
13. What is the altitude during operation? Below 10,000 feet ________, Above 10,000 feet ________
14. How much of the time is the truck spent idling? Hours/day __________
15. Is the driver technique or operating practices affecting fuel economy?

• High road speed: mph __________
• Operate at rated speed or above: rpm __________
• Incorrect shift rpm: Shift rpm __________, Torque Peak __________
• Operate at a cruise speed: rpm __________
• Believe compensating for low power: Yes ________ No _______

If after filling out this form it appears that the problem is not caused by vehicle factors, environmental factors, or driver technique, fill out the Driveability/Low Power/Excessive Fuel Consumption Checklist and go to the Fuel Consumption Excessive performance tree.

This form can be copied for convenience.

Oil Consumption

In addition to the information that follows, a service publication is available entitled Technical Overview of Oil Consumption, Bulletin No. 3379214.

Cummins Engine Company, Inc. defines “Acceptable Oil Usage” as outlined in the following table.

Engine Lubricating Oil Consumption Report
Owner’s Name		Date of Delivery			Engine Serial Number
		Month	Day	Year
Address		Equipment Manufacturer			Engine Model & HP
City	State/Province		Equipment Serial Number		Fuel Pump Serial Number
Engine Application (Describe)	Oil and Filter Change Interval				Complaint Originally Registered
	Oil		Filters		Date	Mile/Hours/KM
Lubricating Oil Added
Date Added Oil	Engine Operation Miles/Hours/Kilometers		Quarts – Liters Oil Added		Brand and Viscosity of Oil Used
Start Test
Last Mileage/Hours/Kilometers _________________________ Minus Start Mileage/Hours/Kilometers ___________________________________
Equals Test Mileage/Hours/Kilometers ____________________________ Divided By Oil Added __________________________________________
Equals ___________________________________________ Usage Rate________________________________________________________________
Customer Signature		Cummins Dealer			Cummins Distributor
Cummins Inc. Form 4755

Oil Consumption Report
Customer Name:	Dist/Dir:
Engine Model:	Mi/Km/Hr:
Engine Serial No.:	CPL No.:
Vehicle Make/Model:	Date:
Review of maintenance history: List any previous failures that could have had a detrimental effect on cylinder component life. Failures could include fuel, coolant, and/or foreign abrasives in the oil, second ring groove beat-out, filter plugging, etc.
Lube Oil Used: Brand Viscosity Change Interval (mi/km/hr)
Combination Oil Filter: Model Element Change Interval (mi/km/hr)
Bypass Oil Filter: Model Element Change Interval (mi/km/hr)
Full Flow Oil Filter: Model Element Change Interval (mi/km/hr)
Air Cleaner: Make and Model Change Interval
List any external engine leaks.
Visually check for any internal leaks and list. Check turbocharger seals, valve guides, air compressor, etc.
Had the fuel pump been tampered with? __________ What is maximum rail pressure readings? __________ If yes, the pump must be reset to factory specifications and the customer sent out to re-evalute his oil consumption rate and the eligibility requirements must be met again.
Warning: Governmental agencies have determined that used engine oil is toxic and carcinogenic. Avoid breathing, injestion, and excessive contact. Drain and refill oil pan to check dipstick markings and notes findings.
Only after above checks are completed, leaks corrected and proper documentation is completed, disassemble engine to determine cause for the failure and repair as required.
State reason for oil consumption.
Signed: __________________________________________________