trayballs

I have a 1994 toyota Extra cab 4x4 with V6 and manual. It jumped time back in may. And after a bunch of troubleshooting found out it had jumped time on the passenger side cam. It was 180 degee's off on just the passenger side cam. So I checked the Cam gear and crank gear, and everything looked good, like the belt just jumped teeth on the passenger cam. The belt is a gator belt and only has 20,000 miles on it, and looks brand new. So I just put it back in time and it ran fine for about 250 miles till it jumped time again. So I tore it apart again and this time i replaced the timing belt tensioner and fan pully bracket. thinking that would fix the problem. Well I got another 300 miles out of it and it jumped again. I havent tore it apart yet, because I'm not sure what to replace. I was thinking of putting a new belt and new injectors and while I have the intake off, pull the valve cover off and look at the passenger side cam real good. Any help is appreciated.

HighLux

Makes me think cam is trying to sieze. Id investigate.

rattlewagon

they normal only jump a tooth or 2, not 180*. something is definitely up.

trayballs

thanks,
Yeah, I'm going to try and fix the 3.0 one more time. If it jumps again I have a 98 explorer with the 5.0 V8. Going to work on buying all the adapters to instal it in the truck.

crazytexan

iTrader: (1)

180* consistant every time? Thats crazy jumping. Its almost like the sprocket is spinning on the cam. like that little retainer rod /key way roll pin is broke and bolt isnt tight. if the cam seized momentarily, wouldnt that wreck ship on the belt teeth on a noticable level after the first or second time?

trayballs

Yeah thats what we figured the first time, but it all looked good. Its backfireing now and barely runs. I haven't tore it apart yet to know how much its off this time, but it didn't backfire near as much the first two times it jumped. Do you think its possible that the fuel injectors acting up could cause the cam to sieze for a split second? If the cam bearings look good, I'm lost at to what is causing it.

trayballs

I had just changed the oil and added the lucus oil additive to the oil last time I retimed it.

bone collector

lucas wouldn't make it jump time like that. Im thinking your cam dowel is breaking or timing belt tensioner is going bad, making the belt go slack and having the cam jump time

bone collector

http://personal.utulsa.edu/~nathan-b...67timingbe.pdf

trayballs

Yeah, I was thinking the lucus would help keep oil on top of the motor to prevent it from happening again. The tensioner is brand new. I'll pull the cam gear off again while I have it apart. Thanks for all the info. I love the truck, its my little run around truck and hunting rig. Its quiet and goes anywhere. Just didn't want to jump into a V8 swap until I have the money to do it right.

trayballs

Well, she's running again, this time I pulled the cam gear to look again. The knock pin looked a little short, and there might of been a little bit of a shinny part where the knock pin spun around on the timming gear. So just to make sure it couldn't again, I made a longer knock pin out of a drill bit, so it will rule out the cam gear jumping. Then I replaced the timing belt and front crank seal. After looking closer at the belt, it was pretty oily compared to the new one. The oil could of been coming from the crank seal. So it's running for now, if it does it again I'm going to have to look at the cam I guess. Thanks for the help

scope103

Why did you think that? When you took it apart, did you CONFIRM that the cam was out of time? If the cam was actually more than 2-3 teeth out of time, 3 of 6 cylinders couldn't fire. I can't imagine you could even get it to run.
I wouldn't do that. A drill bit is hardened, and so is significantly weaker in shear than a knock pin. What size bit did you use, by the way? A knock pin (obviously) is not an SAE size.

I've heard others talk about "jumping time," but I find it really hard to believe you could jump a TOOTHED belt without destroying the belt. (even 1-2 teeth). I think something else is going on.

trayballs

I used a 3/16 drill bit, the knock pin was .197 of an inch or 5 mm. I used the drill bit to make the cam hole a little bigger and then cut it the right length. It worked out good to where the cam gear didn't have any play in it. I looked for a longer knock pin, but couldn't find one. Yeah I agree that it might shear easier than the knock pin, but is there really that much tension on the cam while its running? It was 180 degrees off again, just like the first two times, and it would still run with a bad miss and backfiring. I think the timing belt had oil on it from the crank seal leaking, so with a new belt and seal, so i can rule that out from the problem too if it does it again. I don't know, I guess all I can do is drive it and see if its going to leave me on the side of the road or limping it home.

scope103

Interesting. The cam turns at exactly 1/2 the speed of the crank. The driver's side cam determines the ignition timing.

So if you put the crank at 0° and found both cams 180° "out of time," that doesn't mean anything. Just give the crank one more turn and both cams will have their marks pointing straight up. I assume what you mean by "180° out of time" is that the cam mark on the passenger side was pointing down at the same time as the driver's side cam's mark was pointing straight up. This would mean that the plugs on the passenger side were firing at the top of the exhaust stroke, and none of those three cylinders would produce any power.

To my way of thinking, that's not a "bad miss." I doubt it would run at all on three cylinders.

Since I don't believe a cam can magically twist exactly 180° (at all, and certainly without shearing all the teeth off the belt), I still think something else is going on.

bone collector

Im with scope with this one. Something else is definitely going on. And a drill bit for a new cam dowel pin?? Im assuming you have never broke a drill bit when you have been drilling a piece of metal. And a drill spins at 1500-2000 rpm, and your motor will spin at 4-5k rpm, ( with a LOT more torque than a drill ). Im all for being cheap and thrifty but I think your playing with a ticking time bomb in this case... best of luck

YotaWoRx

I have an extra passenger side cam. PM me if you're interested

Gevo

I would disassemble and start reassembling the head. You should find the problem then. I would be afraid that mickey mouse fixes could lead to bigger problems.. Allthough I am totally for the 'duct tape and WD40" fix when it's appropriate .... interesting problem.

Punchy

Drill bits break at the cutting edges, There is an area that fits into the chuck that rarely breaks.
It will work since both are harden.


The 94 uses a hydraulic tensioner, There might be oil pressure issue at it.

trayballs

Yeah, the timing mark on the passenger cam gear was at the bottom again while the driver side was on its top mark. It would still crank up and run somehow. I would put it in low range to move it into the shop. I'm a little worried now about using the drill bit. I will probably find a dowel pin, and change it out when I can. Going to take the truck hunting this weekend. Only beacause I'll be close enough to call a friend if it breaks down again. I'm planning to install the upgraded fuel injectors when I take the intake off again to look at the passenger cam. Do y'all have any suggestions on which injectors are the best to buy? I was looking at the Bosch with the 4 holes in them. Thanks for all the help.

RJR

Maybe I'm not understanding this correctly, but it would seem that a broken dowel would not give you the result you're seeing. The cam would be out of time with a broken dowel, but the gear should still be happily rotating in time with the cogged belt. For the cam gear timing marks to be out of phase, the belt has to have jumped some teeth. Why it would be 180 degrees worth every time is a bit of a mystery, however.