Removing the front pully from the crank shaft

[isuzufan]

I need to replace the timing belt on a 3.1 turbo diesel 96 Mu but I can't get the bottom pully off the crank shaft. The main nut will not loosen.
When I try the whole crank rotates. Some vechiles have a hole in the pully that a nut or bar can go through that screws into the block to stop the crank rotating. I have been unable to find a way to stop it rotating. It is an Auto.
Any help would be great.
Thanks
Sydney

Thanks for replies. I would leave the pully on but I have to remove it to get the plastic cover off that covers the cam belt, half of the water pump etc. It is also behind the crank sharft pully.
I have remove the radiator and everything else including the 4 bolts that are around the large nut on the bottom crank shaft pully. I am not sure what these 4 bolts do, I guess they are to stop the pully rotating on the crank sharft as they have to be bolted into the crank shaft as well.
There are another 4 bolts that hold the covers over the cam shaft (toothed) sprockets. This is to stop the cam belt from working its way off the front of the sprocket.
I guess I have to lock the fly wheel as sugested adn try this.
Any other sugesting welcome.
Sydney

[geeves]

Do not undo the large nut under any circumstances!! Its nearly impossible to tighten back up with the engine in place. Torque is 150 foot pound from memory. Double check this if you have undone.
You should be undoing the 4 shall bolts around the outside of the big bolt.
If the large bolt comes loose it destroys the keyway in the spacer behind the pulley which allows the valve timing to move which can kill the engine. It can also damage the crank.
Only way to lock the engine is to take out the starter and lock a screwdriver in the ring gear. On a manual you can also put in top gear

[timster]

If you lock a wrench with a socket against the ground and then turn the starter a tiny bit, the bolt comes off easily. So far no problems after 120k.

I tried taking the 4 small bolts off, but it wouldn't budge. Do you have more information on this method?

[geeves]

Ive never done my own timing belt but watched it done on mine after the bolt came loose and fell out 70000km from the time it was done by a mechanic as the car still had a warranty. On mine it all came apart easily but the cambelt was able to move more than a tooth either way

[mulover]

When i did my cam belt i just removed the 4 small bolts and took the plate off that they held on, then slid the belt off. The motor was still in place but i had the radiator out.

[Harry]

Remove the 4 8mm bolts and tap the pulley forward gently with a soft metal hammer.I've tried a rubber hammer but it doesn't seem to give the right kind of shock.There's also another bolt retaining the plastic cover behind the pulley.
Hope this helps.
Harry.

[James W]

also see the simular thread;

clubisuzu.proboards.com/index.cgi?action=display&board=Engine&thread=3551&page=1

the pics toward the bottom may help

[isuzufan]

Thanks the pic's make it much clearer.

[ken]

I had this problem with my 94 Bighorn a few years ago. I could not get it off by driving with a brass drift or with a puller I made up.
So I had to use some lateral thinking. The pulley is dynamic balancer so gets some vibration. After removing the belts I took out the 4 small bolts. and replaced them with bolts where the threads finished just short of the bolt head. I had to cut some of the thread off as they were a bit long. I carefully tightened the bolts up until they were thread bound with sufficient washers under so that the washers
were just loose. I then ran the engine for a few minutes blipping the throttle occasionally and checking it if it was free. After a few minutes I could hear it clicking, stopped the engine and it was loose.
People using this method will be obliged to send me a chocolate fish for all the bruised knuckles I have saved them. LOL
Ken