Forum:
diahatsu fourtrak 2.8td 1994 black smoking when pulling off slowly smoke clear when put your foot down and engine is shakng really bad on idle a frend of mine been looking at it and engine is running realy hot and and ad the injectors checked they all ok had the push rods checked and theyok aswell the valves seem to be moveing ok checked the conrods at tdc so been told must be the pistons or rings . this engine has had a new head on be four i got it and dont no y .eny ideas please
Hi and welcome.
Hi.
Assuming the fuel pump has not been fiddled with.
New owner or has this problem gradualy appeared, is this from cold, or even when hot !!!. If cold it could be due to failed heater plugs, they continue to heat for a while after starting.
Q - what is the tickover/idle RPM
Tickover/idle RPM ought to be around7/800 RPM when hot,can be adjusted with, if present a screw knob adjuster on the dash ( though this was designed for ancillary equipment such as winches), proper adjustment should be made on the injection pump). I have found on my truck setting the idle RPM at 800, when hot, has increased the cold starting idle RPM, this increases to 800 as the engine warms up, hpe this makes sense.
As clear on exceleration assume air filter and injectors okay ,would replace fuel and air filter as a matter of course, price is peanuts !!
Edward (ews) '92 Fourtrak 2.8 TDX
In the service manual it
In the service manual it states that the idle speed when hot should be 650 +/- 25rpm.
From the F70, F75, F77 manual.
What difference will a higher idle speed make, unless you are doing it for extended periods of time? Will 800/900rpm idle really ruin an engine?
idle RPM
Hi.
The idle speed set by the pump is approx 650/700 RPM, as I run a 50/50 veg oil mix I have used the hand throttle/screw aduster to get a higher cold tick over /starting rpm. This then drops back to approx 650/700 RPM as the truck warms up. This seems to help cold starting re the mix I use, and is for better words the engine less lumpy when cold. Also I believe the smoother cold at tick over running, helps avoid stresses on the cam belt, this is just my percieved view.
Edward (ews) '92 Fourtrak 2.8 TDX
Sounds like an injector going
Sounds like an injector going down, at idle they show such traits. Go to an injection specialist who will remove and test and recondition them for you.
Interesting comment
I allways thought that the injector pressure/ spray pattern was the same ,irespective of the rpm of the engine (re the Fourtrak system). I also would like to admit I should have suggested in my previous post, that one could have, by having the injectors tested, which would may have possibly removed them from causing the problem.
Edward (ews) '92 Fourtrak 2.8 TDX
You are partially right
You are partially right Edward, the spray pattern and delivery pressures are the same virtually, irrespective of engine revs.
It is the injector break pressure which is controlled by a spring and shimmed which determines when the fuel is injected. This spring is shimmed to set the break pressure and over time the spring becomes weak. This reduces the break pressure and injects too soon and at too low a fuel pressure for the pintle to effectively atomise the fuel correctly. This leads to a poor spray pattern, and instead of a fine sppray it emerges as a coarse spray and drips of fuel. It is this which causes poor running and black smoke; it also carbons up the pintle and affects the actual spray pattern.