I have a 1998 Mitsi minicab, 12 valve, U41T (2wd) with the 3G83 660cc engine. I have just done a partial rebuild, new piston rings, skimmed head, head gasket etc. I see that the oil pump/balancer can be set at different positions even when the engine is at top dead center with all timing marks correct due to the fact the oil pump/balancer shaft sprocket is geared. I have spun it many times with the engine apart and have no idea where it was before I took it apart (but I did not take out the oil pump/balancer shaft). Is it important how it is oriented with the engine at top dead center with all timing marks correct. Anyone who has done this or has looked how it works/rotates will know exactly what I mean. For every 3 turns of the cam sprocket, the oil pump/balancer sprocket will turn exactly 5 times (I think I counted that right), and it can be oriented in 5 different positions with its own timing mark pointing at its own corresponding timing (TDC) mark. Any help appreciated. Thanks.
It’s quite important, 1 out of 4 revolutions will be balanced. If it’s off it will vary from a little vibration to rattling your fillings out. Hopefully this image explains it well. The toro pdf manual is better than the “factory” Denko manual I have.
Hi Bowe, thats really great to have that diagram. I guessed that it would be out of balance and vibrate if not correct. I had a quick look but do not understand what is meant by point 3, Timing Belt Installation. I cant understand what 'plug hole on left side of cylinder block' refers to, where that is? Any ideas? The way I am reading this is, once I know where the plug is, set the engine to TDC all marks lining up, remove the cam belt, stick the 65mm long piece of rod through the hole, if 65mm will not go in, keep turning the balancer pulley one revolution at a time, checking each time to get at least 65mm in, put the cam belt back on? Many thanks again, Mark
It’s a 10mm head (if I recall correctly) plug on the left side of block (when seated in truck) easier to see from under the truck since the block is canted so far that direction. I believe I used a suitable length 5/16” bolt in leu of an 8mm rod. You won’t have to worry about checking the 65mm depth it will either slip past the balancer shaft and go in or it will not want to go in much at all. Are you referring to the repeat step 3 part? It does read weird but it’s just saying if you don’t get the proper range of motion to remove rod and spin balancer to try again. Found a decent picture of the same plug on a 3g81. It’s in that same general location.
Hi Bowe, Perfect, thanks so much for your time on this, I see the plug now. I think I understand now, and yes I was referring to the repeat step 3 part, basically the 8mm or 5/16" rod might go in the right distance (or not) but you have to then see if you can move the balancer shaft sprocket clockwise 4 to 5 teeth, and counterclockwise 1 to 2 teeth even if its in the right distance. If it doesnt, you rotate the sprocket one more revolution clockwise and repeat. Kind of makes sense now, ensures the balancer shaft is in exactly the right orientation. I'm actually looking forward to doing this now. This is the second time I have had this engine out, the first time I rebuilt part of it I never did any of this, I dont remember it having noticeable vibration but might just have been lucky, this time it should be perfect. I ordered the James Danko manual for the Minicab a few days ago, but might seek out the Toro manual also. I already have a Toro PDF, but it does not look like your screen shots, doesnt have this info, Thanks again, Mark
Hi oscott5, thats great info, especially the picture at the bottom of that first page showing the 8mm piece next to the balance shaft. Really appreciate it, I feel confident I can do this now. Thanks.
so if all the timing marks are lined up, that is THEE only point where the rod must go? Are there not multiple positions where the marks would all line up? They wouldn't align at TDC compression and exhaust? And if there is only that spot, only the pump gear is turned so the rod goes? Not the crank? So it's done before the timing belt is on?
Yes only balancing shaft is turned to time it correctly after cam/crank marks are lined up. There are multiple gears behind pump/balancer gear, that why the rod only lines up every 4th rotation. The rod is simply checking the position of a balancing lobe inside engine. Sounds complicated but if you read and follow the manual it’s quite simple.
If I line evrything up before I pull the belt off, is it even necessary to do the balancer check? I really wanna make this as quick and painless as possible. I'm 69, and spent way too much time laying on the couch this past winter, and I dread working in such a tight space. I DO appreciate your reply.
No, but it would still be wise to insert the rod with everything timed. The balancer spins so easy it’s not hard to lose its position. I didn’t spin mine back the right way so I got the joy of tearing it down and doing it again after feeling the new vibrations.
Edit: Got the timing belt and water pump changed. Checked the bal' shaft, all was well. Truly a PITA job for an old man. Took me 2 days to get it done. The old belt looked fine, but knowing it was an interference engine, in a 26 yr old truck, made me too paranoid to even drive it. Only 20k miles, but the age worried me. My plugs were 11/16", and even tho' it's a 6 valve head, I had to thin down the end of the socket to get it onto the plug, due to the shield surrounding the plugs. I'm still not sure I've got all the air out of the coolant system. Also,.... Is the 6 valve head definitely interference too??
