Technical Information · issue 20 of 1994
Water pumps P 835, P 840
IssueTI 20/1994
Full text
Page 1 of 6
Technical Information
20.94
New water pumps STIHL P 835 and P 840 - type 4702
1. General description
The new water pumps P 835 and P 840 are The water pump P 835 can deliver up to 12 m3/h
extremely light, handy and yet robust machines. (self-priming up to a suction lift of 5.5 m), while the
They are primarily intended for irrigation and P 840 can deliver up to 30 m3/h water.
drainage purposes on farms, in gardens and on Delivery heights up to 45 m and 35 m can be
building sites. achieved with these pumps.
The water pumps are driven by the tried-and-
tested engine attachment 08 S with a
displacement of 56 ccm. Page 2 of 6
Technical Information 20.94 - Page 2 2. Technical description 2.1 Engine The power unit is based on the same compact two-stroke engine that is also used in the 08 S chain saw and in a number of STIHL BT and TS series. The robust design permits its use even in tough conditions. It is mechanically designed to prevent accidental contact with hot engine parts. 2.2 Pump The pumps operate on the centrifugal principle. The pump housing comprises two diecast parts (corrosion-proof aluminium alloy) which are bonded and additionally screwed together. The intake and delivery ports are screwed onto the pump housing. The intake port ends directly at the open blade side of the pump impeller where it is fitted with a vulcanized elastic ring protecting the ends of the blades against abrasion due to impurities. fo The pump impeller (impeller wheel) is made of a bronze alloy. An axial face seal ensures that the pump impeller is sealed off from the pump housing. The seal is made up of rubber and ceramic sealing elements. The water pump P 835 is a self-priming pump up to a suction lift of 5.5 metres. Sufficient water must be present in the pump housing for operation. The water pump P 840, on the other hand, must always be operated with a foot valve which is fitted at the end of the suction hose. The pump and suction hose must be filled with water before it is started up. Water must overflow through the opening in the pump housing in order to ensure that there is also sufficient water present in the suction hose. Important! The water pumps must never be allowed to run dry, otherwise the axial face seal will be damaged.
Page 3 of 6
Technical Information 20.94 - Page 3
3. Technical Data
3.1. Engine
Displacement: 56 cm3
Bore: 47 mm
Stroke: 32 mm
Compression ratio: 9.5:1
Power output (DIN 70 020) 2.5 kW (3.4 PS)
max. torque
at 5,000 r.p.m.: 3.7 Nm
Crankshaft: Two-part, drop forged
Crankshaft bearings: Two deep groove ball bearings
Crankpin diameter: 14.4 mm
Big-end bearing: Needle cage
Connecting rod length: 58 mm
Piston pin diameter: 12 mm
Small-end bearing: Needle cage
Rewind starter: Pawl system with automatic
rope rewind system
Starter rope: 4.5 mm dia., 1000 mm long
Crankcase leakage test
at gauge pressure: pü = 0.4 bar (5.8 psi)
under vacuum: pü = 0.4 bar (5.8 psi) fo
3.2 Fuel System
Carburetor: All position diaphragm carburetor with
integral fuel pump
(Standard setting)
High speed adjusting screw H: Back off approx. 1 turn
Low speed adjusting screw L: Back off approx. 1 turn
Carburetor leakage test
at gauge pressure: pü = 0.4 bar (5.8 psi)
Fuel tank capacity: 2.65 l (2650 cm3)
Octane number: min. 90 RON
Fuel mixture: Regular brand-name gasoline and brand-name two-stroke engine oil
Mix ratio: 1:50
with STIHL two-stroke engine oil 1:50
1:40 with other brand-name two-stroke engine oils
Air filter: Round filter with foam
3.3 Ignition System
Principle of operation: Contact ignition
Ignition timing: 2.0 ... 2.4 mm B.T.D.C.
Spark plug: Bosch WR 7 AC
Electrode gap: 0.5 mm
Spark plug thread: M 14 x 1.25; 12.7 mm long
Heat range: 175 Page 4 of 6
Technical Information 20.94 - Page 4
3.4. Pump
P 835 P 840
Max. delivery height 45 m 35 m
Max. suction lift up to 5.5 m
self-priming,
7 m with foot valve 7m
Max. delivery volume 12 m3/h 30 m3/h
Max. pressure 4.5 bar 3.5 bar
These values refer to:
P 835 11 /4" connection
Delivery height [m] 6 10 14 18 22 26 30 34
Delivery volume [m3/h] 11.5 11.3 10.5 9.0 8.0 6.7 6.0 5.4
P 840 2" connection
Delivery height [m] 6 9 12 15 fo18 21 24 27
Delivery volume [m3/h] 29.0 27.0 25.5 23.5 21.5 19.0 16.0 12.0
● suction lift of 1.5 m
● engine speed of 6700 r.p.m. Page 5 of 6
Technical Information 20.94 - Page 5
3.5 Tightening Torques
The specified tightening torque must be maintained in order to ensure that the screw connection has the re-
quired strength. It is therefore essential to use a torque wrench.
Fastener Thread For component Torque Remarks
size
Nm
Spline screw M 4x15 Set of contacts 1.0
Spline screw M 4x12 Fanwheel 7.0
Spline screw IS-M 4x16 Armature plate 3.3
Spline screw IS-M 4x25 Carburetor flange 3.3
Nut VM 5 Filter port 4.5
Spline screw IS-M 5x18 Fan housing 5.0
Spline screw IS-M 5x18 Guard, fan housing 2.8
Spline screw IS-M 5x25 Guard, crankcase 4.0
Spline screw IS-M 5x28 Crankcase 6.8
Spline screw IS-M 6x20 Handle 4.3 1)
Spline screw IS-M 6x25 Tank housing to crankcase housing 7.0
Spline screw M 6x90 Muffler to cylinder 8.5
Nut M6 Muffler to housing 8.5
Spline screw IS-M 6x20 Cylinder 9.5
Spline screw
Nut
IS-M 5x18
M 10x1 Flywheel
Shroud/crankcase housing 2.0
27.5
1)
M 14x1.25 Spark plug 25.0
Spline screw B 4.8x13 Rubber buffer 1.5
Nut M6 Inside of housing to engine 8.5
Nut M 10x1 lks. Rotor to crankshaft 24.5 1)
Spline screw M 4x19 Ignition armature 3.3
Spline screw M 4x10 Air baffle to crankcase 2.3 1)
Nut M6 Intake port 6.5
Spline screw IS-M 5x18 Delivery port 5.3
Spline screw IS-M 6x25 Tank housing to pump housing 7.0
Remark
1) Screw must be secured with adhesive 0786 111 1101 (LOCTITE 243).
Note: Screws secured with adhesive are easier to release if the adhesive is heated first with a hot air blower
(hair dryer). Excersise caution on polymer components!
3.6 Weight
P 835 P 840
(total) 8.4 kg 7.9 kg
3.7 Dimensions
(H x W x D) 380 mm x 350 mm x 300 mm
3.8 Accessories
Combination wrench 1107 890 3400
Screw driver
T27x120x70 0812 370 1145
3.9 Special Accessories (Service)
Carburetor parts kit 4702 007 1060
Set of gaskets 4702 007 1050 Page 6 of 6
Technical Information 20.94 - Page 6
4. Special tools No. Repair job
P 835, 840
The same special tools as for the chain saw 08 S 4702
can also be used to repair the engine unit of the wa-
ter pumps. 1 Starter mechanism with
starter pawls 15
2 Shroud, air filter, carburetor
5. Repair times and muffler 35
3 Ignition module, switchgear,
The following repair times are specified for trained ignition armature 40
4 Pump housing with
personnel and a fully equipped customer repair shop. pump impeller 20
5 Cylinder and piston 60
The repair times are specified in minutes. 6 Crankcase and
crankshaft
155
7 Crankshaft bearings and
Note: The table of repair times for the water pumps rotary shaft seals 145
P 835 and P 840 can be added to the STIHL Table 8 Pressure-testing the crankcase 30
9 Trial run1) 5
of repair times (page 15) (either cut along the dotted 10 Tank 15
line and paste into the table or transfer the values 11 Handle, stop switch,
by hand). throttle control 5
1) Only with water or without pump
The applicable national safety regulations and the sa-
fety instructions in the User Manual must be complied
with if the machine is started up during repair or main- fo
tenance work. ✂
Waiblingen, 30 March 1994 Andreas Stihl
D1/MTK-al Technical Documentation Extracted from the manufacturer's 2012 service catalogue. Most of these PDFs embed fonts with a shifted character map, so the text above was recovered rather than copied — read it as a faithful but imperfect transcription, and treat the page image above each block as the authority where the two disagree — the figures exist only there, because they are vector drawings that text extraction cannot keep.