Ford F-750 - 2. Engine Tune-up

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8

Chapter

I-General

Engine Repair

carburetor

float.

Check

the

condition

of

the

needle

and

seat.

Replace

if

necessary.

(c)

Check

fuel

pump

pressure.

If

the

pressure

is

excessive,

the

pump

was

forcing fuel

past

the

float

needle

and

should

be

rebuilt

or

replaced.

c.

Cooling System.

The

cooling

system

is

thermostatically

controlled

to

regulate

engine

operating

temperature

and

provide

for

a

short

engine

warm-up

period.

(1)

ENGINE

OVERHEATS.

Usually,

engine

over-

heating

is

the

result

of

insufficient

coolant

supply.

Check

the

coolant

first.

Make

certain

that

the

cause

of

trouble

is

not

anti-freeze

evaporation.

(a)

If

the

supply

is low,

check

for

leaks

in

the

cooling

system,

make

repairs

as

necessary.

(b)

Check

the

water

pump

belt

for

proper

tension

and

adjust

it

if

it

is loose.

(c)

Inspect

the

radiator

fins for

obstructions

(bugs,

dirt,

etc.).

Clean

it

if

it

is clogged.

(d)

Using

a

thermometer

in

the

radiator,

check

the

gauge

reading

for

accuracy.

NOTE:

Inaccurate

readings

are

sometimes

caused

by

insufficient

clearance

IJetween

the

head

cas

ling

and

the

temperature

sending

unit

element.

Repair

or

re-

place

as

necessary.

(

e)

Check

the

thermostat

for

proper

operation

and

heat

range.

If

defective

or

of

the

wrong

heat

range,

replace

the

thermostat.

(f)

Check

the

ignition

timing

and

adjust

if necessary.

(g)

Check

the

radiator

for

proper

flow.

Flush

the

radiator

if necessary.

(h)

Remove

the

water

pump

and

check

for a defec-

tive

impeller

or

water

passage

obstruction.

Repair

or

replace

as

necessary.

(2)

ENGINE

FAILS

TO

REACH

NORMAL

OPER-

ATING

TEMPERATURE.

Generally,

this

symptom

i~

caused

by

the

thermostat

sticking

or

being

of

the

wrong

heat

range.

Check

the

thermostat

first.

If

the

engine

still

does

not

reach

operat-

ing

temperature,

check

the

gauge

and

sending

unit,

with

a

thermometer

in

the

radiator,

for

accuracy.

Re-

place

the

defective

unit.

2. ENGINE TUNE-UP

During

the

life of

an

automotive

vehicle,

it

should

receive

regular

maintenance

and

inspection

services.

In

addition,

to

maintain

satisfactory

performance,

an

en-

gine

tune-up

should

be

performed

periodically.

Any

type

of

engine

test

equipment

may

be

used

to

make

the

tests

outlined

in

the

checking

procedures.

As

the

checks

are

performed,

make

a

visual

inspection

of

the

wiring,

vacuum

hose, cooling

system

hose,

heater

hoses, etc.

a.

Minor

Tune-Up.

A

minor

tune-up

consists

of

the

following

operations:

(1)

INSPECT

IGNITION

WIRES,

BATTERY

CABI.lES, AND

CHECK

THE

CONDITION

OF

THE

BATTERY.

Inspect

all

ignition

cables

for

worn

or

damaged

insulation.

Make

sure

that

the

spark

plug

wires

are

firmly

seated

in

the

distributor

cap

and

that

the

terminals

and

the

terminal

sockets

are

free

from

corrosion.

Inspect

the

battery

case

for

cracks

and

leaks.

Check

the

water

level

in

the

battery.

Inspect

the

battery

cable

connections for

corrosion

and

clean

if

necessary.

Brush

the

cable

connectors

with

grease

to

retard

further

cor-

rosion,

then

tighten

them.

(2)

TEST

CYLINDER

COMPRESSION.

Operate

the

engine

until

normal

operating

temperature

is

reached.

Turn

the

ignition

switch

off.

Remove

all

spark

plugs.

Set

the

throttle

to

wide

open

position

and

leave

it

open

for

the

test.

Using

a

compression

tester,

test

the

compression of

each

cylinder.

Crank

the

engine

for

at

least

four

compression

strokes.

Note

the

reading

on

the

first full

stroke

as well

as

on

the

final

stroke

to

deter-

mine

if

any

variation

exists. All

cylinders

should

be

tested

the

same

number

of

strokes

to

assure

accurate

readings.

The

compression

of

all

cylinders

should

be

uniform

within

ten

pounds.

Record

the

compression

of

each

cyl-

inder

to

indicate

to

the

customer

the

internal

condition

of

his engine.

A

reading

of

more

than

ten

pounds

above

normal

in-

dicates

carbon

or

lead

deposits

in

the

cylinder.

A

reading

below

normal

indicates

leakage

at

the

rings,

valves,

or

gasket.

(3)

CLEAN, ADJUST,

AND

INSTALL SPARK

PLUGS.

Sandblast

the

spark

plugs,

wipe

the

porcelain

clean, file

the

electrode

tips

flat

and

adjust

the

spark

gap.

Test

the

plugs

in

an

approved

spark

plug

tester.

Replace

any

plugs

that

have

broken

or

chipped

porce-

lain,

badly

burned

electrodes,

or

that

do

not

check

satis-

factorily

on

the

tester.

Install

the

spark

plugs

and

tighten

them

to

the

specified

torque.

(4)

CHECK

AND

ADJUST

TIMING

AND

IN-

SPECT

BREAKER

POINTS.

Disconnect

the

vacuum

line

between

the

distributor

and

carburetor.

Start

the

engine

and

operate

it

at

idle

speed.

Check

the

timing

with

a

timing

light

and

make

the

necessary

adjustments.

Connect

the

distributor

vacuum

line

after

completing

the

adjustments

and

check

ignition

advance

as

the

en-

gine is

accelerated.

Inspect

the

distributor

points

for

pits, excessive

metal

transfer,

and

bums.

Replace

points

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