Mitsubishi 4DQ5 Service Manual download pdf (Page 71)

6-3 Testing

The feed

pump

IS m satisfactory condition when

it

meets all

of

the test requirements hereunder enumerated:

(1) Suction

perfODnllJlee

The

pump

should be capable

of

starting

to

deliver

fuel in 45 seconds

of

its starting

at

150 rpm.

(2) Delivery preauae

Run

the feed

pump

at

600 injection-pump rpm,

with

the

discharge side

of

the feed pump fully

closed.

Under this condition, the delivery pres-

sure should

be

anywhere between 1.S kg/cm

2

(25.6 psi) and 2.2

kg/cm

2

(31.3 psi).

Specification

Unit: kg/cm

l

(psi)

hem

Standard

Feed

pump

delivery

1.8""

2.2

(25.6""

31.3)

pressure

at

600

rpm

(3) Capacity test

Run

the pump

at

the speed specified below and

open the discharge side more

or

less

to

hold the

discharge pressure

at

1.5

kg/cm

l

(21.3 psi) (as

read

on

the test gauge),

with

a measuring glass

cylinder set

up

to

receive the discharged fuel.

Under this condition, the

pump

should'deliver at

least

900

cc (54.9 cu in.)/miDute.

Specifications

Item Standard

Repair limit

900

cc (55

600cc

(37

Feed pump cu in.)/minute,

cu in.)/minute,

capacity minimum at

at

1000 rpm

1000 rpm

(4) Air-tightness

Immerse the feed pump in a pool

of

fuel, with its

discharge side plugged up. Apply an air pressure

of

2 kg/cml (28 psi)

to

its suction

to

see

if

any

bubbles come

out

of

the pump. Some air, however,

will leak

out

through the clearance between its

pushrod and housing. The pump

is

sufficiently

air-tight

if

the

amount

of

this leakage (with no

leakage from any

other

part

of

the pump)

is

not

greater than the value specified.

Specification

Item

Standard

Not

greater

than

50

cc

Feed pump air-tightness

(3.1

cu

in.)/minute (with

bubbles

not

larger than

2mm(0.OS

in.) in size)

If

the air-tightness is

poor,

replace the pump

housing sub-assembly (including housing, push rod

and oil seal).

-67

-

1-Measuring

cylinder

2-Tappet

Air

pressure,

2 kg/cm

l

(28 psi)

---,~

3-Plug

4-Diesel fuel

oil

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