O'Brien PRO 301, Owner'S Manual

15

308–030

PROBLEM

CAUSE

SOLUTION

Paint leaks into wet–cup

Throat packings are worn or damaged

Replace the packings. See page 16.

Excessive surging from spray gun

Spray tip or fluid filter is plugged

Disassemble and clean.

Spray tip too big or worn

Change the spray tip.

Paint too viscous

Thin the paint.

Wrong type hose

Use minimum 50 ft (15.2 m), grounded, flexible
hose (wire braid hose is unacceptable).

Not enough paint pressure

Pressure setting too low

Increase the pressure.

Spray tip too big or worn

Change the spray tip.

Pressure control frozen or damaged by
overpressurization

3

Try to thaw

2

, or replace the pressure control.

Displacement pump worn or damaged

Replace the displacement pump. See page 16.

Tails or fingers in spray pattern

Pressure setting too low

Increase the pressure.

Fluid outlet filter is dirty or clogged 
(if used)

Clean the filter. See page 12 or manual 307–273.

Spray tip too big or worn

Change the spray tip.

Fluid supply is low or empty

Refill and prime the pump. Check fluid supply of-
ten to prevent running the pump dry.

Paint too viscous

Thin the paint.

Wrong type hose

Use minimum 50 ft (15.2 m), grounded, flexible
hose (wire braid hose is unacceptable).

Paint runs or sags

Spray tip to big or worn

Change the spray tip.

Spitting from gun

Air in fluid pump or hose

Check for loose connections at pump intake and
tighten. Then prime the pump.

Spray tip is partially clogged

Clear the tip. See page 11.

Fluid supply is low or empty

Refill and prime the pump.  Check fluid supply of-
ten to prevent running the pump dry.

Static sparking from the gun

Spray or work being sprayed is not prop-
erly grounded

Correct problem before continuing. Follow the
warning section, FIRE OR EXPLOSION HAZ-
ARD on page 3.

1 

The electric motor has an over–temperature switch

which automatically resets upon cooling. If it opens and
the electric motor shuts itself off, unplug the power sup-
ply cord and let the sprayer cool for 30 to 60 minutes.
Always use the lowest pressure setting needed when
spraying.

2 

Freezing results from failure to replace the water–

base paint or flushing water with mineral spirits, and
usually causes permanent damage to the pressure 
control.

3 

Over–pressurization results from (1) using less than

50 ft (15.2 m) of flexible spray hose, (2) from using a
wire braid spray hose, (3) from adding a shutoff device
between the pump outlet and the spray gun, (4) from
attaching a spray hose to the pressure drain valve, or
(5) from using a clogged or incorrectly assembled filter,
if used.