# Sentra timing issue?



## Dezzy (Jul 17, 2013)

Hey guys!

I'm trying to fix my friends 1998 1.6 Nissan Sentra. The upper chain tensioner was worn all the way to the metal. I replaced it, but I'm wondering if the chain might have slipped?

Theres also suppost to be a lower chain, but I havent dug into it yet. 

How do i set timing?

The symptoms that are making me think its a timing issue:
-Good Spark
-Good Fuel
-Smoke/air coming back out of intake
-That tensioner was shot
-No compression when motor spins.

The only experience I have with bad timing was on my 3 cyl metro. When the timing was off on it, it behaved the same way with smoke coming outta the intake. 

Any help would be really really appreciated.


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## jdg (Aug 27, 2009)

You've got more than timing issues if you've got:
A) No compression
B) Smoke/Air coming back out of the intake

I know from first hand experience that 2 teeth will smack valves and pistons.
Short of finding something else that'll cause the same problems (e.g. timing chain fell off, etc.), better plan on pulling the head and having a few hundred bucks worth of work done to it.

I used to live in Jacksonville, Ar.
Glad I got outta there.


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## smj999smj (Jan 1, 2006)

Yeah, those upper chain tensioners are getting to be fairly common on the GA16DE engines with high mileage. Usually they strip the teeth on the timing main sprocket, which connects the upper to lower timing chain. As mentioned, this often results in bent valves.


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## Dezzy (Jul 17, 2013)

It seems to have some compression. It just wont quite start. I turned the distributor as far to the right as it would go with the bolts still in and it almost starts and there is compression, but it wont quite get there. 

Im new to timing chains. so this is a bit of a learning curve compared to working on my metro, which is just a glorified go kart lol.

Next step is to pull the lower sprocket off so I can find TDC and see where everything lines up. 

Will I need to pull that lower cover to figure out where the lower chain is riding? 

Where does the lower chain and upper chain meet? I took off that top cover and replaced the tensioner without any problems, but was expecting to see a lower chain meet up next to the top one or something similar. 

I cant seem to find any step by step guides on how to do this and Ive used that search function. Maybe I'm not using the right terms.? :wtf:

Thanks for all the help so far guys I'm a shade tree mechanic and this is a bit new to me.


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## smj999smj (Jan 1, 2006)

The chains meet at the main gear, which is the lower gear the upper timing chain rides on. The back part of the main gear, which you cannot see with just the upper cover removed, is a larger sprocket that the top of the lower chain rides on. By your description, you definitely have an engine timing issue at minimum. You need to turn the crank pulley so that the timing pointer on the cover lines up with the 0 degree TDC mark on the crank pulley and the timing mark on the main gear is in the correct position. Then you can put the cams so that the timing marks on the gears are in the correct location. There are plated or painted links on the upper timing chain that will need to line up with the marks on the gears. You should be able to find info on the timing chain in the free repair guides at Autozone.com (you need to register an e-mail address). Another thing you can do is remove the camshafts and use a compression tester hose hooked up to an airline to check for bent valves. The compressed air will enter the cylinder. If air blows out through the exhaust or up through the intake manifold, there is bent valves. With the camshafts removed, all of the valves will be closed.


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## wilburk (Dec 29, 2012)

Sounds like it would be very valuable for you to invest in a Haynes manual or Service Manual! Speaking from experience, pictures/diagrams help me a lot more than text. I took on a timing chain job a while ago and it was immensely helpful to have the diagrams and be able to visualize them before I jumped right in.


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## Dezzy (Jul 17, 2013)

Ok I finally figured it out. 

Got it all put together, but the chain is too loose. It just slips on the gears. Idk if its stretched, or if its the lower gear thats been worn down.

How do I tell if a chain is stretched?


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## wilburk (Dec 29, 2012)

Are you sure it's not skipping a tensioner or anything? Or that the tensioner is actually tensioning? If the engine isn't running you aren't going to be getting the oil pressure that's going to tension the chain...


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## Dezzy (Jul 17, 2013)

just went out and checked and yea its completely expanded  

How do I get the chain completely off? It catches on stuff. I'm doing all this for a friend and he doesnt have the cash to get a haynes manual or I'd get one.


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## smj999smj (Jan 1, 2006)

Those chains usually don't stretch a significant amount to cause a lot of play. It is an oil fed tensioner, as already mentioned, so full tension won't be achieved until the engine is running. There is a spring inside the tensioner that will take up most of the slack. As I said earlier, often the teeth on the main gear strip when the upper tensioner fails, so take a careful look at the gear at the bottom of the upper timing chain.


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## JWinston (Jul 1, 2014)

I'm sorry to inform you ,but you need to pull the head,I suspect you may have bent valves.I suggest you also do an oil pressure check you may have some worn bearings.


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## BeyondBiscuits2 (Jan 18, 2006)

There is a right and wrong way to install the upper timing chain. The slack needs to be on the intake side, as where the exhaust side should be tight without any play. Also, make sure your engine is at TDC before you do anything in regards to timing. But, before I did anything else, I would rent a compression test kit from your local parts house and make sure you have good compression in your cylinders. If not, sounds like the cylinder head needs to come off before you keep beating a dead horse.


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