Blue/white Smoke on Decel Coasting

[Cruzer!]

Hi all, Ive done a search but couldnt find what i was looking for...

I've got my 60 which i did a head reco (inc port matching) on a few months back, and upped fuel pressure and it goes pretty well for the old truck, only problem is when i am going down a hill or relying on engine braking (foot Off Acc/Brake/Clutch) it blows white/blue smoke. It doenst do it under acc or any other time (maybe a little at startup) but no matter how long i've been driving it will do it under engine braking, and its pretty thick... Any suggestions on anything to do besides re ring that could fix this?

Thx

Ben.

[Beefcake]

this is usually the symptom of rooted valve guides or valve stem seals. Take it back to whoever re-coed the head.

[Ruffy]

Under decel you create a greater vacuum in the engine beacause it's turning over faster without the throttle open. This vacuum increase will draw engine oil past the valve stem seals and down the valve guides if they are worn or have incorrect clearance. This is a likely cause for your smoke. especially if it has only happened since fitting the head.

[Cruzer!]

cool, will tyr and reset clearnaces see if that helps... does anyone run tighter clearances than what the manual says? will it help? and if so, what do u run?

[Ruffy]

cool, will tyr and reset clearnaces see if that helps... does anyone run tighter clearances than what the manual says? will it help? and if so, what do u run?

Running tighter clearances will help you to have a reason to pull the head back off when the valves burn out!

[ferrit]

diesels dont tend to get a greater vaccum when you coast as they dont have throttle bodies to restrict the amount of air entering the combustion chamber- its a full gulp every piston cycle, you alter fuel to alter torque output.

right?

[Ruffy]

diesels dont tend to get a greater vaccum when you coast as they dont have throttle bodies to restrict the amount of air entering the combustion chamber- its a full gulp every piston cycle, you alter fuel to alter torque output.

right?

2H has a throttle body!!!!!!!!!!!!!!!!!!!

[Cruzer!]

yeah 2h is diffucult it has a throttle body with vacuum and pressure lines to move fuel pump diaghrpagm (to many bundys, and honestly couldnt spell it if i was straight )

[tweak'e]

i don't know the 2h motor at all but ill give ya 2 cents worth anyway!

usually if a deisel has a butterfly it has an EGR system. vaccum will depend on if the EGR system is working or not.

upped fuel pressure

?? how did you do that?

if its white smoke its usually means incomplete combustion, which can be a few things. first suspect would be injection pump timing.

[dumbdunce]

i don't know the 2h motor at all but ill give ya 2 cents worth anyway!

usually if a deisel has a butterfly it has an EGR system. vaccum will depend on if the EGR system is working or not.

upped fuel pressure

?? how did you do that?

if its white smoke its usually means incomplete combustion, which can be a few things. first suspect would be injection pump timing.

2H has a throttle butterfly to control fuel delivery but it does not have EGR.

fuel pressure is controlled by the injectors so it is possible to increase fuel delivery pressure by deviating from manufacturers specifications when rebuilding injectors, but it also requires the pump to be re-timed and the delivery volume to be adjusted. if you just shim the injecotrs and do nothing else the timing will be retarded and delivery volume will be low.

if this is what has happened then it is likely to be the cause of your smoke. if your timing is retarded and/or your injectors have been fiddled with, ten you are also likely to notice crappy performance and ordinary fuel economy.

although it is possible that the smoke is due to worn valve guides and/or valve stem seals, the 2H does not make a lot of vacuum at coast and even if it does draw some oil in, the oil is likely to be completely burned.

the other possibility is that your motor is just plain worn out and is drawing oil up the cylinder walls on coast.

1. get a compression check
2. get the pump timing and delivery checked
3. worry about valve stem seals and valve guides after 1 and 2 yield no results

cheers

DD

[tweak'e]

2H has a throttle butterfly to control fuel delivery but it does not have EGR.

cheers for that

just windering how the butterfly work for fuel control?

[dumbdunce]

2H has a throttle butterfly to control fuel delivery but it does not have EGR.

cheers for that

just windering how the butterfly work for fuel control?

there are two pipes connected to the throttle body - one above the throttle butterfly and one below. the other ends of the pipes are connected across a diaphragm on the fuel pump which is connected to the rack in the pump. with the throttle closed, there is a big pressure difference between the top and bottom so the diaphragm is pulled towards the 'slow' end. as the throttle butterfly is opened, the pressure equalises and the diaphragm moves under light spring pressure to the 'fast' end. it is done this way to smooth out the throttle response especially in rough terrain where your foot can bounce on the throttle.

[tweak'e]

2H has a throttle butterfly to control fuel delivery but it does not have EGR.

cheers for that

just windering how the butterfly work for fuel control?

there are two pipes connected to the throttle body - one above the throttle butterfly and one below. the other ends of the pipes are connected across a diaphragm on the fuel pump which is connected to the rack in the pump. with the throttle closed, there is a big pressure difference between the top and bottom so the diaphragm is pulled towards the 'slow' end. as the throttle butterfly is opened, the pressure equalises and the diaphragm moves under light spring pressure to the 'fast' end. it is done this way to smooth out the throttle response especially in rough terrain where your foot can bounce on the throttle.

another interesting gadget explained. cheers