I recently did my first timing belt job on my 1996 5sfe. It took a lot of trial and error for me to make sure the belt was installed with the proper tension, and so that timing marks stayed aligned.

Here is a summary of the procedure that I used.

1. Set the timing marks before putting on the belt ( the hole in the cam shaft sprocket and the notch/dimple on the crankshaft sprocket)
2. Put the belt on and tighten the tensioner.
3. Then rotate the engine with a wrench on the crankshaft pulley a couple times
4. Recheck the timing marks. When I did mine the timing marks were now off by a few teeth, because I couldnt get have the belt tight enough between the cam shaft and crankshaft sprockets.
5. I would then rotate the engine until the camshaft was on TDC, then inspect the crankshaft timing mark to see how far it was off. If only by a few teeth I would mark the tooth on the crankshaft and the point on the belt that SHOULD be aligned if the engine was in time. Also mark the an alignment position point for the belt on the camshaft.
6. I would then take the belt off, rotate the crank until it was now at TDC ( the camshaft should not have moved and would still be at TDC)
7. Put the belt back on with the alignment marks you made for the camshaft and crankshaft.
8. Rotate engine again, check the timing marks and repeat process as necesssary.

Also, dont forget to tight down the tensioner when you are checking the time. I forgot to do this a few times, and the belt would jump teeth, after a spent time getting it perfertctly aligned!

Good luck,
brian

 

When checking the TDC and the 10 o'clock cam pulley notch, also take a look at the belt ... looking for a little slack on the underside of the top cam pulley.
If you observe that the belt has slack at the top pulley, just take the belt off enough so that you can shift the belt tooth placement by one notch, and then replace it on the cam pulley. If everything is correct, the timing marks will be lined up and there will not be any apparent slack on either side of the top cam pulley. ...

Also be sure that everything is tightened appropriately ... as mentioned previously.

 

Did you remove the Cam gear AND crankshaft gear when replacing timing belt to put on new seals?

If not the cam gear pin or crankshaft woodruff key could be the problem, also make sure all the teeth on the crankshaft gear are intact.

New Timing belts don't just slip

 

Thanks for the feedback from everyone. I had a chance to work on it yesterday morning. It looks like the tensioner wasn't tight enough. I realigned the belt, made sure everything was tightened to spec and all is good. It's running great!