RickRoth

Hi folks,
My water pump needed replaced and it was past due for timing belt replacement anyway. When taking the belt off I got a little ahead of myself and forgot to turn by hand till the timing marks were on TDC or actualy 50 degrees before top dead center to protect valve/piston impact. In hind site I wish I would have put the belt back on right where sprockets were positioned and then reposition, but I again got ahead of myself and rotated each sprocket clockwise till on timing marks.

After putting everything back together I get NO firing of engine at all, it cranks and cranks with no pops at all. I took it back apart to verify my timing marks were aligned and they are dead on. I checked all connections and everything is connected. This brings me to a couple questions:

1. Is it possible for the crank to be 180 degrees out of sequence with the cams? I know the crank goes through 2 full rotations for each cam rotation since the crank sprocket is 24 teeth and the cams are 48. But I would think when piston #1 is at top dead center as long as the cam marks are lined up it should be correct since crank position is sensed by the timing disc behind the crank spocket, unlike the old days when a distributor could be placed 180 degrees out of sync.

2. If the crank can be one full rotation out of sync what positon can I place the cams in to guarantee I don't do valve/piston damage while rotating the crank one full rotation since this is an interference engine?

Hep!!!! This one has me stumped as this is probably the 8th time I've replaced timing belts and have never had a problem before. I'm pretty sure it is due to my forgetting to set the marks before taking the belt off but just can't see how it can not be correct unless spark is determined by yet another sensor/distributor somewhere else.

salimshah

Instead of repeating ... please read up


https://www.clublexus.com/forums/rx-...erference.html

TDC is based on crank and not the cam gear.

As long as you turn the crank by hand and stop on resistance you cant damage anything. To prevent fighting the compression you can remove the spark plugs.

Advancing beyond tdc #1, is not needed for RX300.

Salim

99rx300541

If the marks weren't lined up right you've more than likely already cause valve damage. I'd check cam and crank sensor wires

salimshah

Not necessarily and most likely not.

One can be 360 degrees (1 rev) out with the crank-shaft and will not have any collision.

On RX300, depending on cam advance (vvt), position you can escape damage.

In any case, it is a must to turn the crank a minimum of 2 turns by hand to ensure the timing is correct to confirm timing is set correctly. When you turn by hand and no go ape at it, you will not cause damage.

I cant guarantee, but most likely every thing will be OK, specially if 2 turns on the crank shaft was done by hand.

Salim

Wht95scort

Are all the teeth on the crank gear? Did you install the large gold washer on and with the bevel out? Where are you checking your marks at?

RickRoth

Thank you all for your help.
As Salim suggested I managed to escape any damage to the valves (at least no apparent miss or rough idle) but turning by hand and being very deliberate and careful. I did remove the spark plugs to make sure I could feel any impact, the rear 3 really were way past due for replacement anyway:-) When I replaced them the last time (engine now has 267,000 miles on it) remembering how tough it was to get to the 3 at firewall prior time I opted to do it later.... As life goes later never happened and so this was the perfect priority to nudge me to get it done...
I was amazed at the condition of the timing belt since it was actually the factory belt! It showed no signs of wear, original printing was still very readable. I know better than leave a belt on for even half that many miles but again, life happens and time flies. I was blessed to not have had a catastrophic failure along the way. I used to commute 70 each way a day so miles add up quickly.
I did note something that surprised me after first rotating crank extra revolution. I was getting spark on the mark on both rotations of the crank. I'm guessing spark is triggered by the crank position sensor?? In any case at first I was wondering if it made any difference. I then remembered someone else on another thread asking about resetting the ECM (I know, shame on me I had not removed the battery ground cable, I rarely do...). After restting the ECM I only got spark on TDC but not till on 3rd time past. Does the ECM normally need a couple revolutions to learn where the timing should be?? And if that is the case if I had just reset the ECM would it have learned correctly wven without realigning after 360 crank rotation??
I have loved this car and has given me such good service over the years I only wish I would have replaced it with another before retiring:-) I love my RX300!!!