Timing Belt Replacement Gone Wrong (1 Viewer)

[TomH]

I put a new timing belt on my 1996 Tacoma 3.4 today and after everything was wrapped up, I couldn't get it to run - it threw an 0340 code which is camshaft position sensor.

I'm almost certain the timing belt is on correctly but wanted to confirm one thing. Before pulling the belt, I turned the crank manually and brought the pulley to 0 on the timing mark. Cams weren't in the proper position so I spun it once more and everything lined up.

Since I replaced the oil seals, I had to pull the cam pulleys. After doing that and putting the pulleys back on, I noticed one side no longer had the marks lined up. It must have jumped when the bolt broke loose. So I just brought it back up to the top and called it good.

So my question is - would this be a problem? My understanding is that as long as the crank doesn't move I should be able to just line up the cams. Is it possible for the cams om one side to be a revolution out?

After I had the problem, I pulled the upper timing belt cover, spun the crank to 0 and the cams lined up just fine.

So I'm leaning towards damage to the camshaft position sensor (CPS) wires. During re-assembly when I went to hook up the CPS, I noticed it was a little short and I ended up removing the timing belt cover to loosen it up. I suspect I pinched the wires. I plan to check this out first.

I also put in new plugs and wires, removed and cleaned the throttle body, new fuel filter and new air filter. I'm assuming none of these would cause the 0340 code.

Any suggestions would be appreciated.

Thanks
Tom

 

[raydouble]

I put a new timing belt on my 1996 Tacoma 3.4 today and after everything was wrapped up, I couldn't get it to run - it threw an 0340 code which is camshaft position sensor.

I'm almost certain the timing belt is on correctly but wanted to confirm one thing. Before pulling the belt, I turned the crank manually and brought the pulley to 0 on the timing mark. Cams weren't in the proper position so I spun it once more and everything lined up.

Since I replaced the oil seals, I had to pull the cam pulleys. After doing that and putting the pulleys back on, I noticed one side no longer had the marks lined up. It must have jumped when the bolt broke loose. So I just brought it back up to the top and called it good.

So my question is - would this be a problem? My understanding is that as long as the crank doesn't move I should be able to just line up the cams. Is it possible for the cams om one side to be a revolution out?

After I had the problem, I pulled the upper timing belt cover, spun the crank to 0 and the cams lined up just fine.

So I'm leaning towards damage to the camshaft position sensor (CPS) wires. During re-assembly when I went to hook up the CPS, I noticed it was a little short and I ended up removing the timing belt cover to loosen it up. I suspect I pinched the wires. I plan to check this out first.

I also put in new plugs and wires, removed and cleaned the throttle body, new fuel filter and new air filter. I'm assuming none of these would cause the 0340 code.

Any suggestions would be appreciated.

Thanks
Tom

Did you have the factory belt with the timing marks on it?

The cams are keyed aren't they? One revolution out wouldn't matter, as it would be back to it's original position.

I'd guess you were right with the wires for the sensor being pinched.

 

[TomH]

Did you have the factory belt with the timing marks on it?

The cams are keyed aren't they? One revolution out wouldn't matter, as it would be back to it's original position.

I'd guess you were right with the wires for the sensor being pinched.

Well, I was wrong on the wires. Still chasing the problem - looks like the belt is going to have to come off for the fourth time. At least I'm good at it now. Thanks for the answer on the cams. I was pretty sure one revolution put it back to where it started but wasn't positive. I had to prove it to myself.

I've moved to Yotatech if you want to follow along there.

Thanks for the input.

Tom

 

[Duane]

Sounds like you may need to start back at the beginning.
Engine positioned to TDC piston#1 and confirm the crank pulley marks line up.
Then confirm the 2 cam shaft pulleys lined up on 12 oclock on their own shafts (1 pulley flange face in and one out)
and then you know the rest of the deal....

 

[TomH]

Sounds like you may need to start back at the beginning.
Engine positioned to TDC piston#1 and confirm the crank pulley marks line up.
Then confirm the 2 cam shaft pulleys lined up on 12 oclock (1 pulley flange face in and one out)
and then you know the rest of the deal....

Can't I just verify the belt is on correctly without starting over? If the timing marks on the cam pulleys are aligned with the timing marks on the #3 timing cover and the timing mark on the crank is aligned with the oil pump body and the intake and exhaust valves on #1 cylinder are both closed, then isn't the belt on correctly?

 

[raydouble]

Did the 34 tooth "gear" that the cam position sensor reads off of get damaged?

 

[raydouble]

Did the 1 tooth "gear" on the RH camshaft that the cam position sensor reads get damaged during the procedure.

P0340
-Open or short in camshaft position sensor circuit
-Camshaft position sensor
-No signal of camshaft position sensor to ECM with enginespeed 600 rpm or more
-RH camshaft timing pulley
-ECM

 

[Duane]

Can't I just verify the belt is on correctly without starting over? If the timing marks on the cam pulleys are aligned with the timing marks on the #3 timing cover and the timing mark on the crank is aligned with the oil pump body and the intake and exhaust valves on #1 cylinder are both closed, then isn't the belt on correctly?

That sounds correct.
If you continued to rotate the crank another half turn and cyl#1 valves stayed closed then you should be ok.
I'm not sure I would want to assume that the cyl 1 intake and exhaust valves being closed isn't a possibility of being at the end of an exhaust stroke and then starting back down for an intake stroke.
I haven't replaced cam shaft pulleys. Are these an alignment pin arrangement so they can not be installed rotated too far or the pulley slid on wrong side first?

 

[ToyotaDon]

Put my 2 cents in your thread on YotaTech.

 

[TomH]

Did the 34 tooth "gear" that the cam position sensor reads off of get damaged?

No reason for me to suspect the gear got damaged (although my thumb got damaged pretty good on the woodruff key when I slid the gear off). It didn't slide right off so I tapped the woodruff key down and had to pry a little with a screwdriver. Really just a little and then I pulled hard by hand. The gear was never dropped or banged around

It is possible it was damaged - but no reason to suspect that.

Did the 1 tooth "gear" on the RH camshaft that the cam position sensor reads get damaged during the procedure.

No reason to suspect that it did. I made an SST out of a piece of plywood and a couple bolts. The force of breaking the bolt loose did cause the cam to jump back a partial revolution. After I removed it I just set it on the little box that houses the cable for the throttle body. It sat there until I put it back on. I remember it didn't slide on easily the first attempt like the left one did so I pulled it off and tried again and all seemed well.

I'm wondering if it is possible the 5 legs of the cam sprocket twisted a little. Doesn't seem likely - but at this point I'm not sure what to think.

It is possible it was damaged - but no reason to suspect that.

P0340
-Open or short in camshaft position sensor circuit

Checks out ok.

-Camshaft position sensor

Checks out ok.

-No signal of camshaft position sensor to ECM with enginespeed 600 rpm or more

Not sure how to check this. When the truck starts it immediately thows a code. Won't idle or run easily.

-RH camshaft timing pulley

Guess this is next on the list.

-ECM

Trying to avoid this one.

Suggestions?
Thanks

 

[TomH]

That sounds correct.
If you continued to rotate the crank another half turn and cyl#1 valves stayed closed then you should be ok.
I'm not sure I would want to assume that the cyl 1 intake and exhaust valves being closed isn't a possibility of being at the end of an exhaust stroke and then starting back down for an intake stroke.
I haven't replaced cam shaft pulleys. Are these an alignment pin arrangement so they can not be installed rotated too far or the pulley slid on wrong side first?

If I rotate the crank from the point of all the marks being aligned, the the exhaust valves open and close followed by the intake valves opening and closing, back to TDC with both valves closed and all marks aligned.

There is an alignment pin on the cam and the pulley has a corresponding notch on the hub. It's a snug fit on the pin. There is probably a couple thousands tolerance but I assume the ECU compensates for that.

Pulleys are clearly marked L and R. At this point I pretty confident the belt and pulleys are all on correctly.

Thanks - I appreciate the input.

 

[TomH]

Problem solved.

Crankshaft gear was missing one of the teeth. Just need to source a new part and do one more tear down and reassembly.

Thanks for all the input.

Tom

 

[Blue77FJ40]

Did the tooth break off, did it fall into the engine? How does the gear it meshes with look like?

 

[TomH]

Did the tooth break off, did it fall into the engine? How does the gear it meshes with look like?

Good questions.

It's really not a gear, not sure why I've been calling it that. FSM calls it the crankshaft timing pulley.

The engine is isolated from the timing belt. The area for the timing belt is a relatively clean area designed to be free from oil and dirt. If it did fall on the engine, it would be sitting on a little ledge below the crank. I've already cleaned a bunch of debris from that area but I'll make sure the tooth didn't end up there. It would actually be nice to find it.

Since it's not a gear it doesn't mesh with anything. It just an outer ring on the crankshaft timing pulley that the crankshaft position sensor reads. The crankshaft and camshaft position sensors feedback info to the ECU so the ECU knows when to send the signal for the spark plugs to fire. At least that's my interpretation of how it works.

A couple pictures.

 

[Duane]

Glad to hear you found it. good catch! I was going to suggest crank or cam sensor next...

that sure seems like an unlikely thing though hey..to lose 1 tooth

Well glad you have it resolved.. good work!

Hopefully Mud helped you rather than Yotatech

 

[raydouble]

Did the 34 tooth "gear" that the cam position sensor reads off of get damaged?

Glad you were able to find it.

 

[TomH]

Glad you were able to find it.

I didn't want to name names because I appreciated everyones help, but there was one person who was first to suggest where the problem might be.

I posted on MUD first because I was hoping you would come to my rescue.

Thanks
Tom

 

[TomH]

Put the new part on after work today and the truck is running great.

Thanks again.

Tom

 

[Duane]

I didn't want to name names because I appreciated everyones help, but there was one person who was first to suggest where the problem might be.

I posted on MUD first because I was hoping you would come to my rescue.

Thanks
Tom

way to go Raydbl...
I'm still wondering how 1 tooth breaks off..did you have the crank pulley off when changing seals?

 

[TomH]

Yep - pulley has to come off to replace the seal. I must have mis-handled it.