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Basic engine fault diagnostic - what's going on here then?
jps - 25/8/16 at 08:33 AM

I'd like to understand what's really going on here if anyone can explain for me...

I'm using a whacker plate (kind of like this thing, but ancient http://hyundaipowerequipment.co.uk/hyundai-hycp6570-163cc-petrol-plate-compactor-wacker)

It seems to have had a tough life - and has been bodged together so the throttle is fixed, the only way of altering the running is with the 'choke' lever on the carb.

It's pull start and - since putting in some petrol which had been standing for a couple of years - it wouldn't run - I found the carb float bowl had water in it. Since draining that out it has been running OK - but here's the strange thing.

It won't start straight off - I have to shut off the fuel supply (it has a gravity feed from a tank) - drain the float bowl using the sprung bleed valve - then it starts. At this point the choke position (it has 3 positions) seems to make little difference. Once running i have a few seconds to turn on the fuel supply - otherwise it stops (no surprise there)...

My assumption is that it's overfuelling somehow? And once it's running it's ok because it can run rich - but it just can't start like that?

gremlin1234 - 25/8/16 at 09:08 AM

is it 2 stroke or 4?

jps - 25/8/16 at 09:25 AM

quote:
Originally posted by gremlin1234
is it 2 stroke or 4?


To be entirely honest - i don't know, and I don't know how I would know!
(Am i right in thinking that the inlet port - i.e. from the carb - would go into the crankcase / or at least go in below the bottom of the piston at the top of it's stroke? Not that that helps me unless I take it apart i guess).

It has an oil dipstick, which goes into roughly where I guess the crank is - are the oil arrangements only like that in a 4-stroke engine?

When i've had the spark out (which comes vertically out of the top of the 'head' I can see a valve opening which rises vertically upwards - I can't see the top of the cylinder though. Not sure whether the presence of that valve indicates it's 4-stroke - in all the diagrams i've seen the 2stroke engines look as though the sides of the piston actually act as the moving part of the valve...?

[Edited on 25/8/16 by jps]

britishtrident - 25/8/16 at 12:24 PM

It is flooding ---carb needs overhauled also fuel valve should be shut off when it is stopped.

What make of engine is it? If it is a Briggs & Stratton or clone the throttle is usually controlled by "windy" govenor, the manual throttle is disable when the engine is installed by crudely bending the throttle controls on the carb.
New plugs usually work wonders for the starting of these engines, the plugs are dirt cheap on ebay.
Briggs & Stratton carbs and " Magnetrons" (actually the transistor assised flywheel magneto) can cause problems but are easily fixed.

jps - 25/8/16 at 02:03 PM

quote:
Originally posted by britishtrident
It is flooding ---carb needs overhauled also fuel valve should be shut off when it is stopped.

What make of engine is it? If it is a Briggs & Stratton or clone the throttle is usually controlled by "windy" govenor, the manual throttle is disable when the engine is installed by crudely bending the throttle controls on the carb.
New plugs usually work wonders for the starting of these engines, the plugs are dirt cheap on ebay.
Briggs & Stratton carbs and " Magnetrons" (actually the transistor assised flywheel magneto) can cause problems but are easily fixed.


Doh! Gravity feed from the tank will flood the carb then? Had not thought of that...

It is supposed to have an actual throttle lever - but at some point in the past I guess the cable snapped - and someone just bolted up/clamped the linkages so it is fixed.

Yep - plug is filthy, got it started the first time by removing the plug and dropping fuel straight into the combustion chamber (elec itself is OK, fairly tingly if I hold the 'HT' lead and pull the cord!).