Finding TDC with the wrong flywheel

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Dobbs

Dobbs

Active Member
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Location
Suffolk
So here's a challenge. I was changing the timing belt on my 12J 2.5 NAD at the weekend. I'd already bought the timing pointer for the flywheel window - as I'd seen the flywheel window and have no bottom plug hole.

But, when turning the crank to fit the timing pointer, I noticed the flywheel was a more modern version with a timing notch rather than EP markings!!. Of course the notch is for the timing plug that fits into the drain hole.

So it looks like I've got a newer flywheel, in an older flywheel housing. With no EP mark, or drain plug hole how do I find TDC?

Cheers
 
could you take a glow plug out cylinder number one, put your thumb over it and feel for the compression stroke of the cycle while slowly turning the engine over via the crank bolt. then mark the flywheel accordingly?

I did that with a petrol engine once, i dont know if the glowplug hole will fit a thumb though lol, do you have any children as they have smaller fingers lol :D

Disconnect the starter solenoid!
 
flat said:
could you take a glow plug out cylinder number one, put your thumb over it and feel for the compression stroke of the cycle while slowly turning the engine over via the crank bolt. then mark the flywheel accordingly?!
Click to expand...

Possibly, but doesn't sound that accurate.
 
remove the rocker cover, rotate the crank pulley until the inlet starts to drop then rotate again until the exhaust starts to drop, measure the distance between and measure the distance between then half it
 
Dr_evil said:
remove the rocker cover, rotate the crank pulley until the inlet starts to drop then rotate again until the exhaust starts to drop, measure the distance between and measure the distance between then half it
Click to expand...

Measure the distance between? The crank position?
 
used a dial guage down injector hole or plug hole before, just put a piece of bar down the most vertical hole and wait till guage stops, that should do the trick, get it close by using the rockers first.
 
The correct way to do it is with a degree wheel attached to the crank (with a pointer attached to the block) and a depth gauge / DTI or similar down the plug hole.
1. Turn crank until No 1 piston is roughly at TDC (use use depth gauge to feel when piston stops rising.
2. Set the degree wheel / pointer so it reads 180 degrees (it doesn't actually need to be 180 but it will make the sums easier than if using zero)
3. Make a note of the figure (180)
4. Turn the crank clockwise until the piston drops exactly 15mm according to depth gauge.
5. Make a note of degree wheel number (say 200 as an example)
6. Turn crank anticlockwise back over TDC until depth indicator reads 20mm
7. Slowly turn crank clockwise until exactly 15mm is shown on depth gauge.
8. Make a note of degree wheel number (say 166 as an example)
9. Subtract '8' from '5' (use your actual figures) In this example 200 - 166 = 34
10. Divide '9' answer by 2 (34/2 = 17)
11. Now turn the crank clockwise by the answer to '10' (using the degree wheel) In this example 166 + 17 = 183
12. When the degree wheel reads 183 the No1 piston is at exactly TDC (the actual figure is irrelevant, it is just used to get the crank in the correct position).

Obviously accuracy is important when measuring the depth.
 
Last edited:
Dobbs said:
So here's a challenge. I was changing the timing belt on my 12J 2.5 NAD at the weekend. I'd already bought the timing pointer for the flywheel window - as I'd seen the flywheel window and have no bottom plug hole.

But, when turning the crank to fit the timing pointer, I noticed the flywheel was a more modern version with a timing notch rather than EP markings!!. Of course the notch is for the timing plug that fits into the drain hole.

So it looks like I've got a newer flywheel, in an older flywheel housing. With no EP mark, or drain plug hole how do I find TDC?

Cheers
Click to expand...

they arent timed tdc but exhaust peak 108 degrees btdc ,just use mark on front of crank pulley and arrow on rear case
 
jamesmartin said:
they arent timed tdc but exhaust peak 108 degrees btdc ,just use mark on front of crank pulley and arrow on rear case
Click to expand...

Ah. should have thought of that before I put the cover back on. I guess the timing marks on the pulleys would have given me the right spot.
 
Dobbs said:
Ah. should have thought of that before I put the cover back on. I guess the timing marks on the pulleys would have given me the right spot.
Click to expand...

as i said they arent timed at tdc so that wont help you ,hole for timing pin should be above cover if fitted for timing pointer
 
jamesmartin said:
hole for timing pin should be above cover if fitted for timing pointer
Click to expand...

Yes, nearly. It's about 10cm out. I can see the hole/slot for the pin whizz past when rotating the crank, but it stops about 10cm past the timing pointer cover. Otherwise, timing marks, and fuel pump are all lined up.
 
Dobbs said:
Yes, nearly. It's about 10cm out. I can see the hole/slot for the pin whizz past when rotating the crank, but it stops about 10cm past the timing pointer cover. Otherwise, timing marks, and fuel pump are all lined up.
Click to expand...


Hi, I know it's a long time ago but did you get this sorted?
My 12j has a tiny slot in flywheel but no pointer.

I'm timing to the manual but still refuses to start!
 
Hi, yes. I kind of ignored it until I took the front timing cover off. When I saw the timing marks all line up at front I was less worried about the flywheel.



Mark22_2 said:
Hi, I know it's a long time ago but did you get this sorted?
My 12j has a tiny slot in flywheel but no pointer.

I'm timing to the manual but still refuses to start!
Click to expand...
 
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