ZCar Forum banner

Status
Not open for further replies.
1 - 17 of 17 Posts

·
Registered
Joined
·
286 Posts
Discussion Starter · #1 ·
I have an 86 nissan non turbo z...i was on base one day drivin to the shopette when i noticed the car idle went to stall but held at about 400-500 RPM...i tried to give it gas and it wouldnt accelerate...and almost died but it didnt...i got to my destination and restarted the car and it was makin a noise(dull clang like would be my best description) synchronized along with the engine firing order so to say....i assumed this car may have jumped timing...but i got half of the timing cover off today and saw that the timing belt was still intact(Thank God).i also tried to start it today too before i began dissasembling the timing belt cover...the engine turned over but gave a weak sustained sputter attempting to run. ive been readin the haynes manual cause my goal is to go ahead and change the timing belt (assuming the valves havent been bent) and replace all seals and stuff. what/where are the timing marks on the camshaft pulleys? are they refering to the L.H. and R.H markings? I only found one notch on the rear timing belt cover am i supposed to be looking on the rear of the timing belt cover....unless im looking in the wrong place? am i suppose to set the engine 20 degrees BTDC before i begin the timing belt exchange?

as i said before i feel that this vehicle has jumped timin but im open to any input anyone has i will be workin on it this week so i need all the input i can get...this is my first time workin on a 300zx...i also have a 1981 200sx



Post Edited (May 15, 10:05pm)
 

·
Registered
Joined
·
430 Posts
This might be right...then again it might not be.....

-------------

Finding TDC after a broken or stripped belt.

1) The EASY method? " just align the crank mark with the oil pump housing one, then align the 2 cam ones with the 2 notches in the back plate? put the belt on and make sure the marks all coincide... all done."

2) The RIGHT method? "Best way to line up cams with crank after belt is broken is to back off the rocker shafts to fully retract all of the valves into the head, then you can rotate the cams and crank into proper position, put the new belt on and then just tighten the rocker shafts back down." Engloid (involves removing the valve covers)

3) The HAYNES method?

a) Remove the spark plugs in order to be able to rotate the engine and to be able to sense any interference as it happens.

b) Assuming the belt is off, the FIRST MOVE (to avoid any more damage) is to get the marks on the cam gears lined up with the backing plate marks by rotating the gears the shortest distance you can to accomplish this. Don't force the gears if you run into any serious resistance other than the cam lobe and spring pressure.

The real question is do you move the crank first or the cam gears? Maybe the shortest move for any gear to get it lined up is best? Move them all SOME in the right direction until lined up? Avoid any interference during this process.

c) If your crank pulley/dampener key is intact and you can get an accurate indication of TDC for the crank, you then need to rotate the crank to TDC (zero degrees).

d) You MIGHT have to align the distributor with the rest of the engine, especially if you've pulled it. Find cylinder number one (look up the firing order in a manual) and trace this wire from that plug to the dist cap.

Take the dist cap off. When finding TDC for cylinder no 1, remember that the engine runs with the timing advanced, so when at TDC, the rotor will point about 15-20 degrees FORWARD (> in the direction of rotation >) of the no 1 wire contact INSIDE the cap.

There might be a couple of marks on the distributor housing to indicate the no 1 cylinder TDC postion. Get the dist in this general area so that you still have some adjustment room on either side at the base.

Might have to remove the bolt and pull the dist out & reset it to get it right. The dist has a sprial-cut gear that rotates some as you pull it or re-insert it...so you need to take this into account.

e) After putting on a new belt and snugging it up to a reasonable tightness, you'd would want to rotate the engine by hand to check for interference. Then you would try to run the engine (plugs in, hoses on, and coolant in) to see if runs OK. If it runs…then you let your breathe out slowly and do the full timing belt replacement gig. If it doesn't; test compression?
 

·
Registered
Joined
·
286 Posts
Discussion Starter · #3 ·
is it true that there is a chance that the valves can be bent if the engine jumps timing?...ive located the camshaft timing marks i just have to get the cranckshaft pulley to it marks....remove it....and the vibration damper off as well...it seems as if this engine hasnt jumped timing but until i get the marks to their respective spot i wont know. i do want to replace the timing belt and tensioner at this time
 

·
Registered
Joined
·
362 Posts
Haynes manual says to remove radiator...lol. I just thought that was funny since that makes the job twice as hard (as far as having to remove the radiator). But it would make it easier, just not necessary.
 

·
Registered
Joined
·
657 Posts
make sure you put a piece of cardboard over the radiator.... so you wont hurt it if you drop something......... i found this out the hard way.
 

·
Registered
Joined
·
286 Posts
Discussion Starter · #7 ·
Thanks Bob...i got the Zs engine to top dead zero with the number one piston on its compression stroke...but the markings on the driverside camshaft dont match with the timing covers markings...the passenger side camshaft is good but the driverside camshaft is off by one notch...so with the crankshaft pulley at its zero degree setting im assuming that the camshaft gears are suppose to be on their respective markings?



Post Edited (May 16, 11:04am)
 

·
Registered
Joined
·
1,530 Posts
just because you got the engine to tdc doesnt mean the marks are going to line up. change the belt and tensioner, line up the marks, and crank the engine. youll find if you set it back at tdc again, the marks wont be lined up. if its still running at all, theres a good chance you didnt bend any valves, you may have only jumped a tooth or two...or three. and the timing marks on the back of the tbelt cover are there. if the paint has worn off or is covered with oil, belt dust, etc... the marks are etched.



Post Edited (May 16, 10:13pm)
 

·
Registered
Joined
·
430 Posts
It's pretty hard for the cam gears to move vs the belt...most likely the crank gear would move...espec if the belt was loose. I'd say it was lined up wrong last belt job.

Time for a new belt and to line it up right...the marks on the cam and crank gears vs the backplate and oil pump marks......should ALWAYS line up at TDC.
 

·
Registered
Joined
·
286 Posts
Discussion Starter · #10 ·
hmm...ok...im convinced that this Z has not jumped timing...the timing belt is still on and it seems to be ok no burs or anything so ive put the car back 2 gether and now i go to start it and the engine turns but it seems as if its just turnning with no hesitstion..what i mean is when i turn the key i hear the starter motor engage and the engine turns but it not a rrrr......rrrrr.....rrrrrr....its a rrrrrrrrrrrrrrrrrrrrrrrrrr (like there is no fire) ya know when a starter motor usually engages there is a fluctuating load on it to turn the engine well the starter motor is just turning the engine. well ive checked the ignition coil and its givin a good spark...fuel pump is doin its job so it seems im lacking spark...hmmm could this be a distributor cap issue?...cause when the car initially stopped running the engine sorta died to a low RPM (400-500) and when i attempted to restart or give it gas it seemed as if it wanted to start but no go...the car has new plugs i changed them when i put the new valve cover and plenum gasket on but i did lack on the wires and the dist. cap so well here goes another shot folks!!!!!!!!!!!!
 

·
Registered
Joined
·
286 Posts
Discussion Starter · #12 ·
compression testing? that the same thing my cousin said...but if i dont get the correct compression from the engine then what does that mean?...well ive put on the distributor cap but its a no go....im about ready to throw this thing away...But then i remember how cool it is riding down the street with the tops down or...layin tracks @ 630 am on the way to work...well ill admit im lost folks and im getting tired...and its hot...im thinkin of findin a service center and let them diagnose it for me...cause i seem to be getting no where....and im runnin outta time...busy schedule next week...ima keep workin with her though...it sucks we only have one nissan dealer here.



Post Edited (May 17, 6:44pm)
 

·
Registered
Joined
·
1,644 Posts
If you get stupidly low compression then that may explain why it won't run and also may suggest internal damage.
 

·
Registered
Joined
·
286 Posts
Discussion Starter · #14 ·
these guys at the auto shop cant even figure out whats wrong with my z...they said there is no compression...and they wanna charge me about 94 bucks to do some inspection..now i ask myself and you all too...what else can cause an engine to loose compression besides valves.....my cranckshaft turns when i use the starter motor to crank the engine...so what else could it be causing a compression malfunction?
 

·
Registered
Joined
·
1,644 Posts
If it is not bent valves then it is the valve timing, or all the piston are holed, or the head gaskets are blown to bits, which you can appreciate is pretty serious stuff and not likely. Not impossible, but not likely.

This may seem like a dumb question, but does your dizzy shaft actually turn when the crank is turning?
 

·
Registered
Joined
·
286 Posts
Discussion Starter · #17 ·
well here's the weird thing....everything does turn...even the engine...someone told me earlier that if the valves were bent or the timing was off then the engine wouldnt even move....after the day the engine died i turned the Z off i..... tried to restart it and it seemed as if it wanted to start but it wouldnt....like there was firing going on but like there was no place or way to resume it....i turned the engine by hand at the crank once i got it home and tore it apart seemed to be effortless...seemed as if it had no resistance whatsoever....so i give it to these guys at this shop and they dont even know whats going on with it and want to charge me a yard and a half to do some inspection on the engine to ensure why it may or may not be gettin compression...maaan im thinkin to myself what if they dont find out what it is then its a yard and a half for nothing....im thinking take the car to base and tear it down myself....and see if i can get to the bottom of this!!!!!!!!!!!!!!!!!!!!!
 
1 - 17 of 17 Posts
Status
Not open for further replies.
Top