1985/05/06 Caterpillar

D346, D348, D349 Engines;
641B, 650B, 651B, 657B, 660B, 666B, 772, 776 Tractors;
773, 777 Trucks;
992, 992B Loaders

SUPPLEMENT: 05/27/85

SERVICE MAGAZINE, MAY 6, 1985, PAGE 10. In the article "System To Find Internal Fuel Leakage" the subtitle was printed incorrectly. The subtitle should read:

D346, D348, D349 Engines; 641B, 650B, 657B, 660B, 666B, 772, 776 Tractors; 773, 777 Trucks; 992, 992B Loaders.

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Reference: This article is reprinted from Service Magazine, August 31, 1978.

Description of Change: A system is available to test for fuel leakage inside the camshaft housings. Fuel leakage can be at different points in the fuel system inside the camshaft housings. The result of this leakage is a mixture of fuel with lubrication oil which can cause an engine failure.

This system uses a new precombustion chamber that has a drain port with a connection to the areas around the fuel nozzle and the end of the fuel line. The drain ports on the precombustion chambers are connected by tubes to the fittings in the camshaft bearing webs in the camshaft housing. Each bearing web has fittings for drain lines from two precombustion chambers. The fittings are connected to drilled passages in the webs that permit any fuel leakage to be drained to the outside of the cam housing.

External (outer) drain lines can be connected to each drain port to keep any fuel leakage away from the hot exhaust manifolds during engine test. If there is a leak, the location of the leak can be easily found and a repair made.

The engine test can then be started again to see if the repair has stopped the leak. After the test, the external drain lines can be removed and plugs installed in the drain ports on the camshaft housing. Pipe plugs are installed in the drain passages at the outside face of the camshaft housing after tests have been run at the factory.

If constant checks of possible fuel leakage are desired, permanent drain lines can be installed, but some precautions must be taken.

1. Only use steel fittings and tubes for the drain lines. Connect the lines to a common point away from hot exhaust manifolds and turbocharger. The common point must be in a location where any leakage can be easily seen.

2. Put the drain lines in location where possible external damage can be prevented. The lines must be held in place by clips to prevent vibration.

If permanent drain lines are not installed, the drain plugs can be removed at different times to check for fuel leakage. These checks can be made without the drain tubes if the engine is cold. Remove the plugs and operate the engine for a short time to check for leakage. Check each drain port. If fuel has come out of the housing at one or more of the drain ports, make the needed repairs. Clean up any fuel leakage. Install the drain plugs again.

A new fitting, used at the points where the injection lines go into the camshaft housing, gives added protection. If leaks start at the fuel line seat at the end of the fitting inside the camshaft housing, the fuel is sent outside the housing through the outer end of the fitting.

Adaptable To: This system is adaptable to all earlier engines when the new parts that follow are installed.