1100 SERIES DIESEL TRUCK ENGINE Fuel System Caterpillar

Fuel System
1.1. Fuel Injection Equipment
2.2. Removing Fuel Injectors
3.2. Installing Fuel Injector

Care of the Fuel Supply: The importance of using only clean diesel fuel cannot be over-emphasized. Buy clean fuel and keep it clean. The best fuel can be rendered unsatisfactory by inadequate storage facilities or careless handling.

Primary Fuel Filter: The use of a primary fuel filter is recommended to ensure that only clean, moisture free fuel is supplied to the engine. Refer to the truck manufacturer's or the filter manufacturer's operation instructions for additional information.

Effort should be constantly expended to prevent contamination of the fuel. An important step is to reduce the number of times the fuel must be handled. When the fuel can be delivered by the distributor to storage tanks and then pumped from the storage tank to the diesel fuel tank, the handling is reduced to a minimum.

Care of the Diesel Fuel Tank: Fill the diesel fuel tank at the end of the day, because the incoming fuel will drive out the moisture-laden air and prevent condensation.

Draining Fuel Tank Moisture and Sediment Accumulation: Before starting the engine drain off any sediment or water which may have accumulated in the fuel tank. In temperatures below freezing, drain shortly after the truck has stopped to prevent water freezing in the bottom of the tank and other low points in the system.

Fuel Filter Change:

1. Unscrew and remove filter (right hand thread).

2. Clean the filter housing base. Be sure all of old filter gasket is removed.

3. Lubricate the filter gasket with clean diesel fuel and fill the filter with clean diesel fuel.

4. Install the filter. Tighten filter by hand until gasket contacts base; then tighten 1/2 turn more.
5. Prime the system.

Priming Fuel System:

1. Loosen the cap on the tee on top of fuel filter base.

2. Operate starter until the flow of fuel from the filter is continuous and free of bubbles.
3. Tighten cap.

NOTE: If engine fails to start, misfires or smokes, further priming is necessary.

4. Loosen each fuel line nut one at a time at the cylinder head.
5. Operate the starter until the flow of fuel is free of air bubbles.
6. Tighten the fuel line nut.

Fuel Injection Equipment

When improper fuel injection is affecting engine operation, a systematic check should be made to determine the cause. A likely cause is dirt or water in the fuel. Drain the sediment from the fuel tank. Install new filter element if necessary. Then prime the fuel system until clean fuel reaches the fuel injectors. If the fuel system is air bound, priming the system will overcome the difficulty.

If the engine is running irregularly, and smoking, a fuel injector may not be spraying the fuel properly.

Testing Fuel Injectors: Whenever an engine performs in such a manner that a fuel injector is suspected or causing trouble, isolate the problem cylinder. To identify the malfunctioning cylinder; loosen the fuel injection line nut at the cylinder head, one at a time, while the engine is running.

When a nut is loosened and the irregularity in running is not affected, this identifies the malfunctioning cylinder. Install a new injector.


NOTE: Never wire brush or scrape a fuel injector assembly as this will damage the finely machined orifices. Your authorized dealer has the proper tools for cleaning and testing fuel injectors.

Removing Fuel Injectors

Before removing or disconnecting a fuel line, clean the cylinder head area around the fuel line connections and valve cover.

1. Remove valve cover.
2. Take out the bolts (A) and remove the fuel return manifold (B).

3. Remove rocker arm shaft and bracket assembly.
4. Remove the fuel injector clamp (4).
5. Disconnect the fuel line (1) and fuel injector line (3) by removing line nuts from the adapter (2).
6. Slide the adapter (2) out of the cylinder head and lift the injection nozzle (3) out of the cylinder head.


Pull injector straight out, by hand, to remove. Slight twisting action is permissible if necessary. Never pry with a screwdriver or other similar tool.

NOTE: Always install new O-ring seals before installing injector.

7. Always install a new compression seal (5) and carbon dam (6) before installing injector. Use needle-nose pliers to remove carbon dam (6).

8. The tool (7) (8S2252) for installing carbon dam (6) is available at your authorized dealer. (This tool must be used when installing the carbon dam.)

Installing Fuel Injector

1. Be sure bore in the cylinder head and fuel inlet fittings are clean.


Never install an injector that has been dropped without first testing it. Examine the tip to be sure it is not broken or cracked.

2. Install a new compression seal and carbon dam.
3. Install a new O-ring seal (4) on the injector (1) and a new O-ring seal (3) on the adapter (2).

4. Install the injector (1) into the cylinder head using a twisting motion. Do not use lubricant in the cylinder head bore or on the injector.


Do not bend the injector inlet connection when installing injector into cylinder head. Bending of the inlet connection creates tension on the injector and causes binding of the needle in the guide and can result in inlet connection failure.

5. Install the adapter (2) and tighten the injector nozzle-to-adapter retaining nut to 30 ± 5 lb. ft. (4,1 ± 0,7 mkg). Hand tighten the fuel injection line.

6. Install the injector nozzle clamp. Be sure all leaves of the retainer are properly positioned around the nozzle body and the retaining bolt is tight.
7. Install the fuel return manifold and rocker arm assembly.


Before installing the rocker arm shaft assembly, back out the lash adjusting screws and make sure the ball ends of the adjusting screws are fully seated in the push rod cups when tightening the retainer bolts. Failure to observe this caution can result in broken push rod cups.

8. Install new bleed boots between the fuel nozzle and the fuel return manifold and new connectors between the bleed manifold and the line connection at the cylinder head. Do not clamp return fuel connection outside the cylinder head.
9. Install retaining bolts and locks. Tighten bolts to 18 ± 5 lb. ft. (2,5 ± 0,7 mkg) and bend locks.
10. Adjust the inlet valve lash to .015 in. (0,38 mm) and the exhaust valve lash to 0.25 in. (0,64 mm). See lash setting procedure.
11. Install valve cover. Install mounting bolts and tighten to 120 ± 24 lb. in (138 ± 28 cm. kg).
12. Purge the fuel lines of air by motoring the engine until fuel, free of air, flows from the connections.
13. Tighten the fuel line connections to 30 ± 5 lb. ft. (4,1 ± 0,7 mkg).
14. Start the engine and correct any fuel leaks that may occur.

GOVERNOR: Check the engine high and low idle RPM at the first oil change period and every 48,000 miles or 1,200 service hours thereafter. Remove tachometer drive cable (or cap) from the tachometer drive housing at front of engine. Refer to chart for high and low idle RPM.


NOTE: Tachometers on the truck dash panel are usually not sufficiently accurate to check high and low idle engine RPM. Always use an accurately calibrated tachometer.