Cyberman

I got this 91 truck from a friend of ours that apparently burned oil. The eninge failed on them, and the dipstick was dry. The engine turns over. I still suspect internal damage, but after pulling the motor and the timing cover, I set the piston to TDC and saw this:



The crank is set properly, otherwise the notch is pointing down and to the left.

I plan on tearing it down completely, but I have a suspicion that the engine seazed momentarily, throwing the cam timing was off. The timing belt has about an inch of play side to side below the tensioner.

Any thoughts?

RC000E

Well, both cam gears are BTDC, but both also appear to be correctly timed. You positive you have the crank set right? Take a pic of that to be certain.

Also, just because the dipstick is dry doesn't mean there isn't oil in the motor. If your tearing it all apart though, then your gonna get all the answers your looking for at that time.

MudHippy

Yeah, check the crankshaft position one more time. The engine shouldn't have been running at all by the looks of it. Something don't jive.

That tensioner doesn't appear to have moved either. It would have to if the belt was gonna have any chance of skipping teeth. If it's still tight and hasn't moved, then forget about it. It'd be pretty much impossible.

Man, that belt do look a bit loose below the tensioner though. But, I'd have to feel how loose it is to tell ya if that's too much slack or not. The way to find out about the tensioner would be to reset it. Loosen the bolt holding it still in the middle of the pulley, if the belt gets tighter below the tensioner there, then it was too loose.

Green93

Edit: Nevermind....I was wrong.

Cyberman

The engine wasn't running, that was my point. It was towed into the shop. And yes, the crank is at TDC, I don't think I need to show a pic of the notch on the pulley against the '0' on the timing marks. I figured if the timing was that far off, it could be the whole reason it doesn't run. Again, I'll know soon if any internals are messed up, just thought I'd see if anyone had an early opinion.

thook

Have you looked at the oil? You could tell if it spun any bearings (if it seized, it did) by the color. It will have a copper, metallic tone to it.

If the crank is at 0* in that pic, those cams are definitely way off. They should be at the mark on the timing cover on the compression stroke.....which it would be if on the marks. (Cam alignment determines compression or exhaust stroke) Where is the distributor in relation to everything? It should be pointing at the #1 plug terminal with the cams at their mark. And to me, that tensioner spring looks way too stretched. There is a test in the FSM for verifying. Since you're rebuilding, you're getting a new one anyway...right?

Here's what you could do. Check the oil first for particles. If you fails that, you have nothing to lose. It's already toast. If it passes....

Drain the old oil...fill with cheapo fresh
Reset the cams and distributor with crank at 0*
Tighten the belt with that flimsy looking spring as much as you can.
If the belt will get tight enough, see if will fire.

thook

Hey, you haven't pulled that motor apart yet have you? Would you try something.....I'm curious. Advance the crank pulley to 12* btdc and see where the cams and distributor line up at that point.

MudHippy

O.k., I hear ya.

But, I've been here awhile now. And I've actually seen this scenario before from another members thread.

He said he had the camshaft pulleys lined up and had pic of what appeared to be the crankshaft pulley at 40* BTDC or something close to it.

Upon closely examining his pic it became obvious that he was looking at a nick on the crankshaft pulley that wasn't the actual timing mark. It was just a small ding on that edge of the pulley. The actual timing mark lined up perfect when he rechecked everything.

Here's the pic.


The way to be sure is look at Fig.210 and then see if your notch is lined up there too.



I guess what I'm trying to say here is your going to have a very hard time convincing me that the timing belt slipped that many teeth. Going by the pic you're showing me anyways. The tensioner couldn't be that loose set where it is there. And these belts DO NOT stretch. Like I said before, if the tensioner has moved any since the belt was installed, that's another story.

Cyberman

I appreciate all of your replies. As far as the motor goes, I actually just pulled the distributor, but everything else is there. I am positive that the crank is at TDC, the 'V' notch on the accessory pulley is umistakable, and there are no other nicks on it to cause confusion.

As far as the belt goes, it is so loose that I can move it to either side of that water pump bolt directly behind it and get a socket on it. I'll get some pics tommorow morning to show the crank, the tensioner may have failed. As for the oil, the mechanic fill it up with used oil, just to see if it would start, so I can't get a color on it.

My guess is that if I reset the timing, it would fire right up.

So now I'm torn between trying that out by putting the motoe back in, or just keep tearing it down to rebuild. I think I'll continue with the latter, as my original plan was to restore this as best I could so that it could last a few more years.

idanity

i just read tonight in a manual, that you can incorrectly line up the pulleys at 180 degrees off, giving a false reading.

try rotating the crank more times to see if they do end up matching the marks.
and
my #1 question, do you have to rotate it in a certain direction
#2 is the fan on a reverse thread

(im planning my own timing belt soon)

Cyberman

I know that's possible, but in this case, the crank is lined up properly.

The engine normally turns clockwise
The fan has 4 nuts, with regular threads. Once the fan is off, the entire pulley assembly comes off with the timing cover.

thook

I think what he means is the "cam pulleys" can be aligned on the exhaust stroke rather than the compression and be 180* off. The crank would turn 2 complete revolutions in order for the cams to turn 1.

Idanity....in that case, the distributor would be pointed at #1 plug terminal, the crank at 0*tdc, but the cams would be pointing directly downward from the mark on the cover. In his case, they are not.

I was curious if someone tried to set the crank at 12*btdc instead of 0*....meaning they misunderstood how to set the timing. If the motor was still together, you could either do as I suggested above or turn the crank until the cams aligned on the mark and see where the crank would sit. If the belt had skipped that many teeth it seems there would be evidence....stripped belt grooves. Unless, the belt was just that loose. And I guess it was. I would suspect the tensioner spring, myself.

I didn't realize the motor was pulled already. In that case, that would be a lot of work to just put it back in. I'd just pull the oil pan and valve covers then to inspect it. I suppose the chances of still having the oil filter is slim?

thook

On second thought, those cams are about 60*'s off.....more than the scenario I was curious about. I bet the belt was just too loose and it slipped. I'd inspect it before you totally rebuild. You may be okay. Then again, burning oil is not good. Blown seals, maybe.

Cyberman

Ya, I'm continuing with a rebuild. The truck has 150k on the clock, and a rebuild would make me feel better than sticking it back in. Plus there is other work to do, like rust management, new suspension, etc.

thook

I'm sure it would. Maybe post back what you find?

Cyberman

I'll keep track of everything, and document what I find out.

Cyberman

Well, I finally got the heads off, and it was a pretty nasty sight. Those of you that have rebuild one of these, did you ever deal with broken rods? How did you get the piston out? I haven't taken the oil pan off yet, but looks like that is the case. It also looks like the previous owner ran on 5 cylinders for quite a while (based on the color of the piston). Also, if anyone can comment on the goo that is the coolant in the one pic? I'm hoping that the block is okay.

thook

It's hard to tell from the pic because of the light, but is the solid matter in that goo-lant somewhat whitish (with some rust, obviously) and chalky?

thook

You have to drop the oil pan to get to the bottom end. The rod bearing caps are in there. If you don't have this, it will help.
http://personal.utulsa.edu/~nathan-b...ne/69cylin.pdf

I hope you have an engine stand. It just makes it easier than working on the floor.....or is that a table you're working on?

Cyberman

It is actually the color of that pic (greenish yellow), it's wet, but I supose it is chalky, if you mean like wet chalk.