Timing belt


#1

I have a 91 Mitzabishi, the engine turns over but the cam is not turning. the thing that is confusing me is that I can’t turn the cam with a wrench but the crank shaft turns freely with the starter motor. What could be jamming the Cam while still alowing the crank to turn. the timing belt is on and tight so I assume the teeth must be sheered of at the Crank pully.


#2

Further disassembly is required. You can’t just stop and wonder. The cover has to come off and then the belt, but why bother? The repair will cost too much anyway. The belt gave way and probably destroyed the valves. The repair will cost at least $1,300. There is a chance that you don’t have major damage because the camshaft is usually hard to turn with the belt on anyway. It’s against all instructions to even try turning the camshaft without positioning the crankshaft properly. You are assuming rightly that the belt is toothless down there.


#3

Mitsubishi what?

Have you watched what happens to the cam pulley and harmonic balancer when the starter is turned? I’d try turning the engine over by hand and observing carefully what happens. I would strongly recommend against using the starter on this thing until you figure out what’s going on, especially if it’s an interference engine, although since you already have any damage is already likely done. You’ll also definitely need to remove the valve cover if you haven’t already done so to inspect the top valve train components.

The crank pulley doesn’t really have teeth-- the timing belt works similarly to a ribbed serpentine belt and is more or less held on by tension. It may be possible that the belt slipped off and is snagged on something else, since the tensioner will automatically take out any slack, but the belt should be visibly crooked from the top. You could have a crank pulley that some how wiggled loose and is no longer attached to the crankshaft or, if things really aren’t going your way, you could have a broken crankshaft.

EDIT: What exactly makes you think the cam isn’t turning? Because really if the timing belt is installed, you shouldn’t really be able to turn the cam, even with a wrench, because even when you try to turn the engine over at the harmonic balancer, you usually have to work pretty hard with a breaker bar and trying to turn the engine over with the camshaft effectively halves the amount of force you’re exerting.


#4

We Have A Year … 91, And Is The Car A Mitsubishi Or Just The Engine?

We need: Make (if not a Mitsubishi car), Model, and engine size, please.


#5

It seems that garbar posted his question, and then went on a long lunch break.
Anyway, for those others who are interested, here’s a little info:
ALL the mitsubishi engines (1.5L, 1.6L, 2.0L, 3.0L) except the 1.8L engine are interference engines. Check Gates: http://www.gates.com/part_locator/index.cfm?location_id=3598
The camshaft won’t turn because it is blocked by bent valves. Replace the cylinder head with one from salvage.


#6

Good Work, Hellokit, That’s Where I Was Going With This


#7

I didn’t have much time last night to do much disassembly, I removed the top belt cover and watched the cam while turning the crank. The truck stop while on the freeway so I already instinctively tried to restart at that time. What ever damage is already done. after observing no movement of the cam I remove the belt from the top pulley and tried to turn the cam with no success. This is all the time I had to work on the vehicle, my feeling is that the valves are bent, but I was hoping someone might have another theory before I actually remove the valve cover and ultimately the head.
Thanks for the response.


#8

Thank you for your response! See response to GreasyJack below. by the way if your paying a machinist $1300.00 for head work I would suggest looking around for a new one.


#9

Mighty Max 1.8 liter


#10

Well, it sounds like you’re pretty lucky since you have the one non-interference Mitsubishi engine, so you can probably rule out a bent valve. Assuming that it’s not just a matter of you not having enough leverage to turn the cam (it shouldn’t be all that easy to turn), your next step should be to pull off the valve cover-- the only thing I can really think of is that maybe a spring or a rocker arm or something came loose and is jamming the cam preventing it from moving. It seems to me that if this happened on the highway, it would have broken the timing belt, but maybe the component coming apart caused your truck to stall and the subsequent starting jammed it in.

At any rate, off with the valve cover!


#11

Thanks GreasyJack I going out in an hour to find out. You have given me a glimmer of hope and thats enough to get into it again. the truck has less than 50 thousand miles, the previous owner drove it with a broken water pump and then gave it to me. I had to shim the head so there is no room left for more machine work. If I have to go to the salvage yard and have a new valve job I will but I was hoping for some optimism and you gave me some. Thanks again!