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#187098 - 14/07/06 09:52 AM Cyclemut or DaveDatsun!--timing belt question
KCX Offline
Member

Registered: 14/10/00
Posts: 1219
Loc: Kansas
I hope this is a quick question for you to answer.

Bottomline in a nutshell:

My timing belt broke while backing out of my driveway. Hopefully I'm one of the lucky ones without engine damage. I did alot of searching on XOC about timing belts, so alot of my questions are answered already.

My question to you about TDC after reading over and over the Chilton book and other opinions:

As long as my two (R and L) camshaft sprockets are lining up properly(dot on sprocket matched to mark on back plate) and the crankshaft pulley was turned and aligned with the left yellow notch to the pointer on the timing belt cover and since the driver's side cam is in place, the rotor in the distributor is pointing at the #1 spark plug wire.....then my engine should be on TDC and ready for the new belt right??? (obviously I placed the new belt with the white belt marks on the gears with the dots)

The books and directions from others talk about putting the engine in TDC when the old belt is still on. Since mine snapped, I wanted to make sure I put it in TDC before I try to start the engine up to see if I'm a lucky guy. Thanks so much for you time.
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#187099 - 14/07/06 06:39 PM Re: Cyclemut or DaveDatsun!--timing belt question
Axle Offline
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Registered: 18/03/02
Posts: 1229
Loc: Fort Carson, CO
It's not going to matter as long as you get all of the lines and dots matched up. It'll take some patience to do it so just take your time. Hopefull you didn't get any valve to piston contact. Good luck.

Axle
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#187100 - 14/07/06 06:39 PM Re: Cyclemut or DaveDatsun!--timing belt question
Axle Offline
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Registered: 18/03/02
Posts: 1229
Loc: Fort Carson, CO
Oh, don't forget to replace the tensioner while your at it.

Axle
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#187101 - 14/07/06 08:17 PM Re: Cyclemut or DaveDatsun!--timing belt question
Anonymous
Unregistered


Ok, had my thoughts screwed up, as you can see below in John Doe's quote....Oh god he's going to love this.... :p

Yep, if your cams are line up with the marks, then you're all set. The crank actually turns twice as often as the cams, not the other way around. I was thinking of turning the crank bolt twice to get the cams lined up, but you don't have to mess with that. Just get all the marks lined up. Install the belt and hit the starter.

You'll be able to run the engine for a couple of seconds without reinstalling everything (I'd put the crank pulley on with the slingers in place, just like normal for this) to see if she's OK. Remember though, you're not circulating coolant like that, so keep the running time low.

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#187102 - 15/07/06 03:29 AM Re: Cyclemut or DaveDatsun!--timing belt question
John Doe Offline
Member

Registered: 24/08/01
Posts: 966
Loc: Chattanooga
Quote:
Originally posted by Cyclemut:
The problem with that scenario is this...

Your cam turns twice for every one revolution of the crank. So you could have the driver's side on the correct 'cycle' but have the passenger's side on the opposite 'cycle' (180° out of time).
If the marks on both cams are lined up, how could either one be 180* out of time? Are there two marks on the cam spockets? I realize the cams could 180* out of time with the distributor, but how could they be out of time with each other if the cam marks are lined up correctly?
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#187103 - 15/07/06 05:25 PM Re: Cyclemut or DaveDatsun!--timing belt question
John Doe Offline
Member

Registered: 24/08/01
Posts: 966
Loc: Chattanooga
Quote:
Originally posted by Cyclemut:
Just get all the marks lined up
Doesn't he also need to verify that the #1 piston is at the top of the compression stroke and not the exhaust stroke by verifing that the rotor button is in the fire position for the #1 cylinder?
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#187104 - 15/07/06 08:04 PM Re: Cyclemut or DaveDatsun!--timing belt question
Anonymous
Unregistered


Not really, as with the cam and crank not connected by the belt any more, the crank only really has two positions at this time, up and down.

The cam position for the #1 cylinder will determine the stroke now, as the cam will determine which valve is opening, closing or if both are closed. If the timing mark is lined up on the passenger's side cam (#1 cylinder side), then the cam is on compression. If the crank timing mark is lined up, then the cylinder is all the way up. And then the driver's side cam just needs to be lined up with the marks, and then the distributor rotor will be automatically lined up with the firing of the #1 cylinder.

Without the cams and crank connected, then the ball game changes a bit.

Great question though.

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#187105 - 16/07/06 03:20 AM Re: Cyclemut or DaveDatsun!--timing belt question
John Doe Offline
Member

Registered: 24/08/01
Posts: 966
Loc: Chattanooga
Quote:
Originally posted by Cyclemut:
Not really, as with the cam and crank not connected by the belt any more, the crank only really has two positions at this time, up and down.

The cam position for the #1 cylinder will determine the stroke now, as the cam will determine which valve is opening, closing or if both are closed. If the timing mark is lined up on the passenger's side cam (#1 cylinder side), then the cam is on compression. If the crank timing mark is lined up, then the cylinder is all the way up. And then the driver's side cam just needs to be lined up with the marks, and then the distributor rotor will be automatically lined up with the firing of the #1 cylinder.

Without the cams and crank connected, then the ball game changes a bit.

Great question though.
My mistake. I thought that the distributor was timed by the crank not the cams. The distributor and the cams do have to be in time don't they (i.e. the valve openings have to be timed with the distributor as so the spark plugs will fire at the top of the compression strokes and not the top of the exhaust strokes)? (Page EM-78 of The 2001 Nissan Xterra ESM says "Confirm that no. 1 piston is set at TDC on it's compression stroke")
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#187106 - 16/07/06 07:41 AM Re: Cyclemut or DaveDatsun!--timing belt question
Anonymous
Unregistered


Yes, the distributor and the cam has to be in time. The cam and distributor are timed together by the distributor gear, and taking the timing belt off won't change the timing between the distributor and cam. The only way that would happen would be if the distributor were physically removed from the engine. Then, you'd have to put the timing belt on, line up all the marks, then install the distributor.

But still, the distributor would have to go back in pointing to the #1 cylinder spark plug wire with that cam lined up with the timing marks. It would just be more insurance to have the timing belt on at that point in time.

And again, all this would only be necessary (retiming the distributor) if the distributor was physically removed from the engine.

As it sits now, just lining up the timing marks and putting a t-belt on would allow the engine to start and run.

Maybe you're thinking that the distributor turns at a different speed than the cam. But the distributor makes one full rotation for every one full rotation of the cam. If the cam's timing mark is lined up, then the distributor will be in the same place every time as well and won't need to be changed or even adjusted.

Now after he puts on a new belt, gets the engine warmed up and such, then he should recheck his timing. Especially if he ever had the engine tuned with a worn belt. The new belt will bring it all back together nicely, and most likely, will change his ignition timing by a couple of degrees. But then again, if the timing was never changed from the factory, then it will all go back to what it was before.

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#187107 - 18/07/06 09:57 AM Re: Cyclemut or DaveDatsun!--timing belt question
KCX Offline
Member

Registered: 14/10/00
Posts: 1219
Loc: Kansas
Thanks Cyclemut for your posts. I figured it out later that evening after I posted and before you posted the first time. After I went over and over in my head how everything should line up and work, then I figured it should work if the cams are lined up with the marks and my camshaft is lined up with the yellow notch on the pointer. I saw that the drivers side cam controls the distributor rotor. As long as you have your cam lined up with the marks, the rotor was on #1 wire. I removed the #1 spark plug and attached a compression gauge before I was going to start it. So I left the engine naked with everything off and just the timing belt to see if the engine will run. It did! A few seconds later, my transmission line that runs through the radiator(I had it plugged with a bolt) started shooting fluid all over the place!...so I stopped the engine quickly.

I went ahead and purchased the rest of the items for the 105k maintenance since I seem to have saved my engine. After everything was installed and completed. I started it back up and all was good! The engine prrrrs nicely. I guess I'm one of the lucky ones! Funny, I have done every kind of maintenance on this X, but only put off the timing belt...funny that is what got me....lesson learned!

Thanks all for your posts.
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#187108 - 18/07/06 11:03 AM Re: Cyclemut or DaveDatsun!--timing belt question
OffroadX Offline
Member

Registered: 17/08/00
Posts: 13692
Loc: Baltimore, MD
So how many miles are on your truck?
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#187109 - 19/07/06 04:08 PM Re: Cyclemut or DaveDatsun!--timing belt question
KCX Offline
Member

Registered: 14/10/00
Posts: 1219
Loc: Kansas
Approx 135K....purchased new in 12/99
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