TM-5-3805-254-14-P-2

TRUCK, DUMP, 20 TON, 6X4, ON-OFF HIGHWAY 71,000 GVW, IHC MODEL F-5070 (CCE)

TECHNICAL MANUAL; OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT, GENERAL SUPPORT AND DEPT MAINTENANCE MANUAL (INCLUDING REPAIR PARTS INFORMATION AND SUPPLEMENTAL MAINTENANCE INSTRUCTIONS)

JUNE 1980

TM-5-3805-254-14-P-2 - Page 469 of 894

TRUCK SERVICE MANUAL

FUEL SYSTEM

Leakage Checks

The plunger to body and plunger to cup leakage check

gives a measurement of fuel bypass between plunger

body and plunger cup to help determine if injector is to

be rehoned or can be calibrated and reused in an

engine.

ST990 Injector Leakage Tester

The ST990 Injector Leakage Tester was developed and

released in order to make available to the field a

standard tool to accurately determine the degree of

acceptability of used injectors.

Fig.

6144.

The ST990 performs tests on all current Cummins PT

injectors except L series.

These tests are as follows:

1. Body to plunger leakage in area below the

metering orifice.

With

the

plunger

retracted

off

the

cup

seat

by approximately 0.048 inch

[1.22 mm], air is forced through the cup spray

holes past the body to plunger clearance and is

measured with a precision flow meter.

This

check supersedes the body to plunger leakage

test on the ST790, In which injector delivery with

a 0.

inch [1.3 97 mm] restrictor orifice is

compared to delivery with the standard 0.011,

0.013 or 0.020 inch [.28, .33 or .51 mm] orifices

(depending upon injector model).

2. Cuptoplunger seat.

The plunger is seated in the

cup with 200 lbs.

[90.72 kg] load.

Any leakage

is measured in bubbles which are released

under a fluid.

level.