To : TECH@WW

By G8MNY (Updated Aug 13)
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Only had experience of one, a 6kW Clarke diesel generator, it weighed in at 150kg and has a 12BHP engine all in a weatherproof noise reducing box!

Top Hatch
ÚÄÄÄÄÄÄÄÂÄÄ~~~~~~ÄÄÄÄÂÄÄÄ¿
³ Fuel ³ Decomp| ³
³ Tank ³ Valve| ³
ÀÄÂÄÄÄÄÄÙ Injector || ³
Electric³ Fuel |ENGINE|| ³
Panel_³ Tap | ||Fan³
³Ú - - - - -¿| Inj- || ³
³|ALTERNATOR|| pump || ³
³| || ||12V³
³| || Sump ||Bat³
ÀÄÄÂÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÂÄÄÙ
ÀÄÙ ÀÄÙ

It was a little used generator that had been stored for years, initially the main problem was dead battery, on starting, we soon found rubbish in the fuel tank blocked much of the fuel line system...

Plastic Electric Injector Cylinder tank----Tap------In line------Bleed----solenoid-----fuel-----injector---unused
on case fuel filter Screw fuel valve pump return

When this had been cleaned out & a new filter put in, all seemed well for a 9 day radio summer camp with it.

However our wet British summers soon found that water got into the fuel tank. The low fuel sensor was placed in the top of the tank in a large molded recess, this of course filled up with water on a rainy day and the only way out was straight into the tank!

ÚÄÄÄ¿ ÚÄÄ¿ Water capture area ReturnÚÄÄÄ¿
³ ÀÄÄÄÅÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙÀÄÙ ³
³ Low PLASTIC ³
³ fuel FUEL ³
³ sensor TANK ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ÚÄÄÄÙ
Tap Feed

Rubber seals & self taps into a thin plastic tank used by the maker are a silly idea! Draining off 2L of fuel into an empty clear drinks bottle, showed just how much water was getting into the fuel. (bottle now part of tool kit)

Diesels with hand start options, have an extra cuylinder valve or open the intake valve for one full engine cycle to initialy stop the high 22:1 or greater compression (decompression lever), this enables enough speed to be built up for a proper compression starting stroke.

The Solenoid Tap
Fairly straight forward plunger device.

ÜÜÜÜÜÜ
±ÚÄÄ¿±Coil ß Steel Case
±³ðð³± ð Return Spring
±³ðð³± Û Soft Iron Plunger
ß³ÛÛ³ß ² Attached Rubber Seal
³ÛÛ³ ³ Brass tube
³²²³___
À´ÃÄÄÄÄInlet
Outlet

On testing one annoying problem was the electric fuel solenoid, this only operated on starting if battery > 11V or the engine was running. It was NOT open if electrics were just in the "ON" position!

Poor Battery Starting
To overcome the fuel being shut off when the battery is slightly weak on starting. Crank the engine over on decompress for several seconds before releasing the decompressor. This gets quite a bit of fuel in the cylinder, that will burn on the compression stroke even the fuel valve does shut off on the heavy compression stroke starter battery load.

The Injector Pump
This is one of the most complex parts in a diesel, it gives variable volume at very high pressure. e.g. 30 atmospheres or 450PSI at a few degrees before top dead centre of the engine cylinder's compression stroke.

Outlet
à ´ Ball
ÚÄÙðÀÄ¿Valve The timing cam strikes the follower
Pump ÃÄÄøÄÄ´ and the small piston moves fuel
Cylinder³Þ ÛÛÛ³ through the ball valve until the
³ÞÜ ßÛ³__ diagonal slot aligns with the inlet
Piston³ÞÛÛÜÞÚÄÄÄInlet port when the output is stopped.
with fuel³ÞÛÛÛÛ³
slot ³ ÛÈÍÍÍÍ Throttle Arm
ÃÄ Û Ä¿ (Piston rotation) The throttle arm is a sliding key
ð Û ð on the piston that controls piston
ð Û ð Return angle and hence the fuel volume.
ð Û ð Spring
ð Û ð
ÜÜÜÛÜÜÜ
Cam Follower

The Injector
This takes the high pressure fuel pulse and injects it in an atomised form into the engine cylinder.

Clamp plate
ÜÜÜÜÜÜÜÜÜ
PressureÚÄÄÄ¿_ Difficult to draw here, the
Valve³ÜÜÜÚÄInput high pressure input causes
³ð ð³ the pressure valve to let fuel
Fuel _³ð ð³Spring suddenly pass through to the
ReturnĿ߱߳ microscopic spray holes.
ÜÜÜÜÜÜÜÜÀ¿±ÚÙÜÜÜÜÜÜÜÜ (Usually 4 of them).
ÜÜÛ Spray|±|Spray ÛÜÜ
ÜÜÛ ÀVÙ ÛÜÜ Fuel that does not get through
ÜÜÛ Pin ÛÜÜ the holes is returned back to the
ÜÜÛENGINE CYLINDERÛÜÜ tank when there is combustion.

WARNING: High pressure sprayed fuel is very dangerous, it will easily go through your skin or affect your eyes. So a cover must be used to test the injector action. e.g. half a clear plastic bottle!

Generator Governor
This works in a similar way to that of petrol generators. Force from spinning "Bob weights" is used to balanced against a preset speed (Hz/volts) spring and the difference used to move the throttle arm. Note that a drop in revs is needed to open the throttle!


See also my Tech bul on "Petrol Generators for /P SSB"


Why Don't U send an interesting bul?

73 de John G8MNY @ GB7CIP

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